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Microbes and the Next Nitrogen Revolution
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Environmental Science & Technology

Cite this: Environ. Sci. Technol. 2017, 51, 13, 7297–7303

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https://doi.org/10.1021/acs.est.7b00916

Published May 23, 2017

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Abstract

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The Haber Bosch process is among the greatest inventions of the 20th century. It provided agriculture with reactive nitrogen and ultimately mankind with nourishment for a population of 7 billion people. However, the present agricultural practice of growing crops for animal production and human food constitutes a major threat to the sustainability of the planet in terms of reactive nitrogen pollution. In view of the shortage of directly feasible and cost-effective measures to avoid these planetary nitrogen burdens and the necessity to remediate this problem, we foresee the absolute need for and expect a revolution in the use of microbes as a source of protein. Bypassing land-based agriculture through direct use of Haber Bosch produced nitrogen for reactor-based production of microbial protein can be an inspiring concept for the production of high quality animal feed and even straightforward supply of proteinaceous products for human food, without significant nitrogen losses to the environment and without the need for genetic engineering to safeguard feed and food supply for the generations to come.

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The Haber Bosch Process: An Invention that Changed the World

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Thomas Malthus (1766–1834) stated that the increasing human population would suffer hunger because of the limited capacity of the earth to produce food crops. (1) This would particularly be caused by the lack of reactive nitrogen, the critical factor in agro-production. About a century later, in 1908, Fritz Haber patented the Haber Bosch process, so-called “synthesis of ammonia from its elements”, which led to the production of synthetic fertilizers and stepped up agricultural production intensively. (2) This has allowed the human population to grow to 7 billion. At present, per unit of biological fixed nitrogen, more than 3 units of Haber Bosch derived nitrogen enter the plant based production chain of protein and calories. (3) This represents around 80% of the total Haber Bosch produced nitrogen and requires about 1% of the total annual world energy expenditure. (2) While the Haber Bosch process itself is optimized and is reaching near thermodynamic process efficiencies, (4) the subsequent use of the Haber Bosch nitrogen in agriculture suffers from many losses. These include, leaching, runoff and volatilization, which result in high inefficiencies and a set of indirect detrimental environmental impacts. This so-called nitrogen cascade effect (3, 5, 6) particularly relates to the production of plants destined to feed livestock, with a large fraction of croplands being devoted to produce protein-rich animal feed like soybean and cereals. (7) As shown in Figure 1, if 100 units of reactive nitrogen are used in the agro-production system, only 4–14% end up as consumable protein, (8, 9) illustrating the inefficiency of conventional agriculture based protein production chains and the need for a more sustainable and efficient path. Almost half of the reactive nitrogen is dissipated when used to fertilize fields, causing serious environmental damage and affecting human health at a global scale (because of, for example, water and air pollution). (10-14) Moreover, these externalities also come with serious economic repercussions for society at large. Indeed, recent studies highlight the enormous scale of the externalities of reactive nitrogen pollution (see Table 1), on the order of the estimated benefits the fertilizer industry constitutes for the agriculture.

Figure 1. Amount of Haber Bosch nitrogen required and its fate during the different protein production routes. The orange and green fractions represent the amount of reactive nitrogen lost or retained, respectively, within the protein supply chain (expressed in percentage of total input, i.e., 100%). The vegetarian- and animal-product-based protein supply routes are adapted from ref 52. A nitrogen uptake efficiency in the microbial protein production step of 90% was assumed; all other losses were based on Galloway and Cowling. (52)

Table 1. Recent Studies Highlighting the Significance of Environmental Costs of Reactive Nitrogen Pollution

region	ref	costs of reactive nitrogen pollution
China	54	This study estimates that agriculture accounted for 95% of the NH₃ and 51% of the N₂O in China in the year 2008. In the same study, it was also estimated that the total atmospheric emissions of reactive nitrogen causing related health damage ranged US$19–62 billion per year. Of this number, agricultural-induced emissions accounted for more than 50% of the costs (in 2008 US dollars).
EU	55	This study revealed that the costs of agricultural-induced reactive nitrogen losses exceed the economic benefit because of increased primary crop production by a factor of 4. Overall, the annual costs associated with agricultural reactive nitrogen losses was estimated to range between €35 and 230 billion per year (equal to ∼38–251 billion -in 2008 US dollars).
USA	56	This study is the first assessing the cost associated with reactive nitrogen losses to the biosphere from human activities in the United States. The study revealed that the total potential environmental and health economic impact of reactive nitrogen losses from anthropogenic nitrogen summed up to an average of US$210 ($81–$441) billion per year in the beginning of the 21th century. Of this, ∼75% of the estimated costs were associated with agricultural induces losses. Costs are in 2008 US dollars or as reported otherwise in the manuscript.
World	19	In this report, conducted by the European Nitrogen Assessment, a costing procedure based on the European situation was implemented aiming at calculating the global cost of nitrogen pollution. Taking into account that the global costs would be approximately a factor 3-fold of the European situation, resulting in an overall estimated costs associated with reactive nitrogen losses ranging between 200 and 2000 billion US dollars annually (in 2008 US dollars).
USA	57	In this study, the Air Pollution Emission Experiments and Policy (APEEP) model (an integrated assessment model) was used to determine the economic impact of air pollution by means of air quality modeling, exposure, dose–response and valuation for a large range of point sources, based on data of more than 10 000 sources measured by the United States EPA. Costs for NH₃ and NO_x emissions are estimated at $900 ($100–$59 400) and 250 ($20–$1780) per ton NH₃ and NO_x, respectively. No information is given regarding year of reference.
USA	58	This study aimed to determine the environmental and health externalities associated with the production of different agricultural crops such as corn and switch grass for the production of ethanol. While the purpose and crops used are different, the externalities are directly assessed based on the emissions of NH₃ and NO_x. Estimated costs (in 2008 US dollars) for NH₃ and NO_x emissions were $3.03 ($1.25–$4.80) and 14.6 ($2.0–$27.27) per kg NH₃ and NO_x, respectively.
USA and EU	59	In this study, the findings of several previous studies (60-62) on the externalities of reactive nitrogen emissions in terms of health, ecosystems/coastal systems, crop decline and climate change were summarized. Costs were estimated at €3.1–€30 kg NH₃–N (to air), €13–€43 kg NO_x–N (to air), €5–€54 kg Nr (to water) and €2–18 kg N₂O–N (to air) which equals to $3.4–$33 kg NH₃–N, $14–$47 kg NO_x-N, $5.5–$59 kg Nr and $2.2–$120 kg N₂O–N when expressed in US dollars. Note that emission data for the year 2008 was used, where the damage costs were derived from studies between 1995 and 2005 and were not corrected for inflation.

In recent years a lot of research has been conducted to address the problems associated with the use of reactive nitrogen in agriculture. Yet so far, proposed solutions favor optimization of existing agricultural practices, rather than advancing agriculture-free approaches. The production of microbial proteins as a disruptive technology has not been described as yet. Here we provide an overview of the need for and expectation of a coming revolution in securing nitrogen for food and feed using microbes as the feedstock rather than traditional agricultural production routes.

The Nitrogen Cycle to Come

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The world’s population is expected to grow to 9–10 billion by 2050. (15) Moreover the demand for high-quality protein will increase as more people converge on more developed countries consumption patterns due to increase in wealth. (16, 17) Estimates by the United Nations Food and Agriculture Organization (FAO) suggest a further 50% increase in N fertilizer demand by 2050, while at the same time recent studies foresee nitrogen losses to the environment of up to 70%. (11, 18) Available mitigation measures to reduce nitrogen pollution include reduced food waste, lower consumption of animal products, better livestock feeding, more efficient fertilization and improved manure use. (19, 20) However, a model estimate (3) showed that even under ambitious mitigation efforts that combine all above measures, nitrogen losses still amount to some 94 million tons per year, well above the critical thresholds for greenhouse gases, air pollution and water pollution (see Figure 2). (3) Under these conditions, it is uncertain whether environmental sustainability thresholds can be reached (3, 21) and that the nitrogen cycle can return within the planetary boundaries. (13, 17, 18, 22, 23) Moreover, implementing these ambitious measures, which include, for example, a doubling of nitrogen use efficiency on fields or halving the consumption of animal products, could be very challenging in political, technological and economic terms. (3) In addition to conventional nitrogen mitigation measures, (19) it is therefore paramount to think “outside the box” for new innovations to effectively decrease nitrogen pollution.

Figure 2. Currently available mitigation measures may not have the capacity to decrease nitrogen losses sufficiently. (3) The scenarios described in the figure are (a) a middle-of-the road scenario of the shared socio-economic pathways, (53) (b) reduction to a maximum of 20% in household waste with increased waste recycling, (c) animal consumption reduced to 50% of western diets, (d) improved fertilization, (e) improved livestock management, and (f) with all mitigation measures in combination. Panels g–i describe a range for critical thresholds for reactive nitrogen related greenhouse gases, air pollution, and water pollution, respectively. Please refer to Bodirsky et al. (2014) (3) for a detailed description of all the mitigation methods, simulated reactive nitrogen flows, and critical thresholds.

Microbial Protein Production Is a Very Efficient Way to Produce Valuable Protein

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An alternative to plant and animal protein is the aerobic production of microbial proteins (MP) by bacteria, fungi, yeast, and algae. (24) Typically, this mode of production involves the supply of nitrogen, an electron donor, a carbon source (can be the donor) and an electron acceptor (e.g., oxygen) to a reactor system enabling highly efficient production and harvesting of the protein. The concept of MP is not new. In fact, methanol based production of bacterial MP was achieved at industrial scale in the 1970s, (25) but a combination of low prices for soy and fishmeal, increased oil prices, the underdeveloped state of the fermentation technology and limited focus on nitrogen efficiency resulted in the discontinuation of it as a production process. The increases in soybean and fishmeal prices in recent years, (26) together with the enormous progress made in industrial fermentation technologies, justifies revisiting the potential of MP as a source of usable nutritive protein. Additionally, the recent findings and increased awareness of the enormous environmental costs of nitrogen pollution (Table 1) make it imperative to rectify this planetary boundary.

A fundamental difference between MP and plant based production of protein is the fact that leaching, runoff and volatilization of nitrogen can be completely avoided. MP production can take place in fully controlled, enclosed and automated bioreactors similar to those widely used in the fermentation processes by the food industry for the production of, for example, beer and yoghurt. As microbes can convert Haber Bosch nitrogen into cellular protein with an unmatched efficiency of close to 100% (24, 27) in such reactor systems, the overall nitrogen efficiency of the total feed/food chain would become substantially higher than conventional protein supply routes. As illustrated in Figure 1, with microbial protein based systems 10–43% ends up as consumable protein, compared to only 4–14% for agricultural based protein production.

Bacteria Can Use a Broad Range of Carbon Sources

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Compared to fungi, algae, and yeast, bacteria have the advantage of not only growing rapidly on organic substrates like carbohydrates, starch, and cellulose but also on gases, such as methane, hydrogen and syngas (i.e., a mixture of CO + H₂) (Figure 3). (28-30) When bacteria are supplied with one of these substrates they can produce highly concentrated cellular protein up to 75 wt % of the dry microbial biomass (24) at achievable protein production rates of 2–4 kg per m³ reactor volume per hour. (25) The latter protein production rates, using naturally available microorganisms, are several orders of magnitude higher than plant based protein production (i.e., up to 3120 tons/hectare per year of microbial protein (9) versus 3–8 ton dry matter per ha per year for conventional soy production). The fact that bacteria can use hydrogen (in combination with carbon dioxide), methane gas or syngas as their energy source opens up the unique opportunity to completely short-cut agriculture-based feed and food production, enabling virtually land free production of MP which concomitantly is less dependent on weather conditions. The process can be placed on marginal land, but also in urban areas. This decreases the pressure on agriculture in general and on high carbon and biodiversity ecosystems in particular. (31) The production of MP using hydrogen, generated through water electrolysis powered by wind or photovoltaic energy would require an additional inorganic carbon source. CO₂ from industrial point sources, such as flue gases from power stations could serve as a carbon source, (32) and would offer the valuable opportunity for large CO₂ emitting industries to substantially reduce their carbon footprint via substitution.

Figure 3. Potential technological pathways for industrial-reactor-based production of MP using different feedstocks with their respective inputs and environmental losses for livestock production and human consumption. Direct upgrading of Haber Bosch generated reactive nitrogen into microbial proteins using hydrogen, methane, or carbohydrates as energy source for microbial growth. Green and gray arrows represent inputs, whereas red arrows represent losses to water, atmosphere, and soil.

Bacterial Protein Production Has Many Additional Environmental Benefits

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Land Use Change, Greenhouse Gas Emissions, and Biodiversity Loss

Agriculture currently constitutes a dominant form of land use globally. According to the FAO, about 5 billion hectares (approximately 38% of the land surface) is currently used for agriculture, either as cropland (12%) or pasture (26%). (33) It is important to realize that agriculture uses the most fertile and suitable land available. A large fraction of remaining terrestrial land on our planet is deemed unsuitable for agriculture and represents deserts, mountains, and tundra. (34) MP production would help to decrease future pressures on fertile land to the benefit of natural ecosystems, thereby, positively affecting biodiversity and CO₂ emissions from land use change. (31) Of particular importance are biodiversity hotspots, such as the Amazon, where a large fraction of the deforestation is related to the expansion of soybean fields. (35)

Phosphorus Pollution

Agricultural loss of phosphorus, another essential nutrient for crops applied as fertilizer in large amounts (i.e., ∼20 Mton P in 2012), (33) through erosion and leaching, is also considered a major environmental burden, already falling outside its safe planetary boundary. (13) Similar to nitrogen, phosphorus losses are completely avoided during the reactor-based MP production process. Note that P losses still can occur in the overall protein supply chain (see Figure 1).

Fresh Water Withdrawals

Agriculture requires major inputs of fresh water, with ∼70% of the global fresh water withdrawals used for irrigation. (36) Reactor-based MP production requires very limited amounts of water (i.e., ∼5 m³/ton MP (27) versus 2364 m³/ton for soy (37)), which can be further reduced if water is recycled or recycled water is used.

Pesticides

MP production does not require the use of chemicals to control weeds or insect pests. Contamination of surface and groundwater with agricultural pesticides is a global environmental and health concern. (38, 39)

Opportunities and Challenges

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Technological Implementation

Large-scale production of MP is connected to certain challenges in terms of growing the cultures, processing the cells to product and assuring the quality of the final product. The obstacles should be, relative to comparable production processes dealing with microbial fermentations, in all respects achievable. The first key challenge is the development of microbial cultures, either as pure culture, as combination of pure cultures or as microbiome. In the latter two approaches, cooperating microorganisms that complement each other to fully use low-value forms of carbon (e.g., CO, CO₂, carbohydrates, methane derived from anaerobic digestion and oils) are present. Such mixed cooperative cultures, which by natural selection evolve to highly efficient biocatalysts are currently named microbiomes. (40, 41) A two-prongued approach can be followed for nonpure culture systems. Microbiomes have been successfully enriched from natural samples to achieve high protein content. (28) One can also use defined cultures to make a mixed inoculum and let it gradually evolve to improved cooperation whereby a predefined ratio between the cell types can be aimed at.

The second challenge is to scale these reactor microbiomes up to a relevant scale and maintain stability as well as guarantee microbial and chemical safety of the resulting product. From the microbiomes, novel organisms can be obtained, complementing the already existing pure cultures enabling protein production. Working with pure and mixtures of pure cultures results in some new challenges, but may lead to a high level of product quality control and facilitated consumer acceptance. On the basis of the substrate, different feeds and foods could be tailored toward a diverse end-use while maximizing usage of substrate. The central element is to come to assemblages of beneficial organisms which at high rates produce in a stable way proteinaceous metabolites. It should be noted that the latter at no point can have negative nutritional attributes, such as raising allergic reactions. On the contrary, they may have certain special properties, such as being rich in high value amino acids or being capable of inducing a stimulation of the immuno-system. (42)

The third challenge (and opportunity) is then to deal with these single-cell microbial biomass rich in protein and transform it to a commodity that has functionalities (e.g., specific taste and odor, the capacity to coagulate and provide structure) that would allow MP to compete in the context of food and feed quality with widely used milk, egg, or meat proteins.

Establishing a Large-Scale Demand for MP

The main challenge for establishing MP as a major sector in the feed/food industry is that it must be accepted by the public as an appropriate alternative to conventional agriculture-based protein. This involves a transition of the existing protein production industries. The protein market is in the order of several hundreds of million tons annually, (27) so in the first instance the production of MP would still rely on Haber Bosch nitrogen.

The direct supply route of MP to human food would be from an efficiency standpoint most beneficial. Even small replacement rates of conventional protein concentrate like soy and cereals could lead to a substantial change in the food supply chain, in particular if it would substitute for animal-based products. A particular issue here can be the regulatory hurdles about food safety and quality assurance that need to be overcome for MP to be fully accepted as a protein supplement. Yet, using carbohydrates to produce fungal protein is already an established concept in human consumption under the name of Quorn, (43) presently produced at some 25 000 ton per year and growing. The main challenge lies in creating a product of competitive texture, nutritional attributes, and taste, which will require applied consumer research involving partners from the food industry. Using MP as feed for animals is comparatively easier, as in the European Union (EU), it is officially recognized and approved as commercial feed for all types of livestock. (44) Moreover, the feed industry is already used to integrating various brewery and distillery yeast-containing products.

Cost Competitiveness of MP

The production cost of MP will depend mostly on the natural gas price and energy costs, which determine the price for Haber Bosch, as well as for substrates like methane or hydrogen. Considering the current prices of natural gas, energy (e.g., for hydrogen production though electrolysis), and carbohydrates on the one hand, (45) and the rising prices of conventional protein (i.e., in particular those of fish meal) on the other hand, this allows MP to be produced at competitive costs. Indeed, methane-based MP, as well as Quorn, are effectively entering the market economy. (43, 46) Similarly important to the MP production costs will be the effective pricing of environmental pollution of agricultural production. MP can reach its full market potential only if the strongly reduced external costs of the food supply chain are reflected in market prices. This requires a shifting of the current policy paradigm away from supporting industrial output-oriented agriculture toward a resource efficient nitrogen economy with a low environmental footprint.

Toward Protein Self-Sufficiency

Having an amino acid composition resembling that of fishmeal, MP will be mainly eligible to replace the protein portion (e.g., soybean meal) within the feed basket, while the potential to replace other feed components (e.g., calories and fibers) is limited. The protein demand of intensified agricultural systems, such as pork or poultry production, is, however, so large that Europe or China (as well as Japan, the Middle East, Korea, and Mexico) cannot settle this demand domestically but have to import large quantities of protein animal feed from Latin and North America. (33) For example, in 2012, the EU produced 96% and 99%, respectively, of the total meat and dairy products available to the European market. However, up to 64% of the total protein-rich feed additives used to support livestock production are currently provided by soybean meal, with domestic EU production only able to cover 3% of the internal demand of soy. (47) This highlights the endemic production and dependence of EU on soy imports, resulting in exposure to price volatility and to risk of scarcity of soybean on the global market. The fact that MP can be locally produced at industrial scale holds the potential for protein-importers, such as Europe and China, to become protein self-sufficient and independent of soy imports.

Concluding Remarks

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The supply of quality protein is of crucial importance for the overall health and wellbeing of the global population. To find a long-term solution to the environmental burdens of our protein-supply chain, we ultimately need to reshape the nitrogen cycle back to its state prior to the Haber Bosch revolution when significant losses of reactive nitrogen into the biosphere did not exist. Contemporary agriculture alone, hindered by its inefficient use of reactive nitrogen, will not achieve this. We therefore foresee a revolution in the use of Haber Bosch nitrogen that allows the radical restructuring of agricultural practices and holds the potential to completely bypass agriculture by directly upgrading Haber Bosch nitrogen into microbial protein for use in animal feed or human food. The new platform does not generate issues in terms of ethics in relation to production animals, genetically modified organisms, and has low water and land footprints. Other routes to protein production should be explored simultaneously to assist in alleviating the environmental burdens. Examples are the use of improved biological nitrogen fixation, (48, 49) engineering nitrogen-fixing cereals (although these types of GMOs would likely face substantial challenges in terms of public acceptance), and developing N fixation by electrochemical processes not involving pressures and temperatures in the Haber Bosch process (50) or even by hybrid nitrogenases. (51) Moreover, some microbes could even use atmospheric nitrogen directly. However, it is questionable that nitrogen fixation would lead to high productivity in terms of cell growth; in the context of MP we are talking about assimilation, not dissimilatory production of a metabolite.

Despite the technical challenges and research needs outlined above, first and foremost the widespread use and acceptability of MP will be dependent on careful and correct marketing to receive overall acceptability from regulators and consumers. Triggering a constructive public dialogue on the mutual benefits for the consumer and the environment as well of this new protein supply route will be essential to safeguard feed and food supply for the generations to come in a sustainable way.

Author Information

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Corresponding Author
- Willy Verstraete - Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Gent, Belgium; Avecom NV, Industrieweg 122P, 9032 Wondelgem, Belgium; Email: [email protected]
Authors
- Ilje Pikaar - School of Civil Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia; http://orcid.org/0000-0002-1820-9983
- Silvio Matassa - Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Gent, Belgium; Avecom NV, Industrieweg 122P, 9032 Wondelgem, Belgium
- Korneel Rabaey - Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Benjamin Leon Bodirsky - Potsdam Institute for Climate Impact Research, 14412 Potsdam, Germany
- Alexander Popp - Potsdam Institute for Climate Impact Research, 14412 Potsdam, Germany
- Mario Herrero - Commonwealth Scientific and Industrial Research Organisation, St Lucia, Queensland 4072 Australia
Notes
The authors declare no competing financial interest.

Biographies

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Ilje Pikaar is a lecturer in environmental engineering at the University of Queensland, Australia. His research has a central theme: recovery of valuable resources from solid waste and “used” water with a special focus on nitrogen recovery and subsequent valorization into microbial proteins.

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Dr. Silvio Matassa is an environmental engineer at Avecom, Belgium. His main area of interest is within environmental biotechnology for resource recovery from used water, with a strong focus on microbial fermentation applied to the upgrading of recovered nutrients and carbon.

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Prof. Korneel Rabaey is professor in Technological Applications of Microbial Processes at the Center for Microbial Ecology and Technology, Ghent University. He is specialized in electricity driven treatment and production processes. An example is electrochemical recovery of ammonia from waste streams for further conversion to chemicals or biochemicals.

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Dr. Benjamin Leon Bodirsky is a researcher at the Potsdam Institute for Climate Impact Research. Designing quantitative models, he investigates the current state and plausible future developments of the agro-food system, with particular interest in long-term dietary change and the environmental consequences on the nutrient cycles and greenhouse gas emissions.

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Dr. Alexander Popp is a Senior Scientist at the Potsdam Institute for Climate Impact Research and leads a research group on Land-Use Management. His research focuses on future land transformations, competition for land, food and water security, biodiversity, climate change impacts, greenhouse gas emissions, land-based mitigation, and climate policy.

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Prof. Mario Herrero is Chief Research Scientist and Office of the Chief Executive Science Leader at CSIRO Agriculture and Food and Honorary Professor of Agriculture and Food Systems at the University of Queensland, Australia. A known team player, with an extensive network of partners and donors, he works all around the world in the areas of agriculture, food security and global change, sustainable development, climate change, and food nutrition.

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Willy Verstraete is emeritus Professor for Environmental Biotechnology and Microbial Ecology at the Ghent University. He keeps exploring the domains of Resource Recovery and Climate Change. Currently, he has set full focus on the topic of nitrogen recovery in general and the upgrading of mineral nitrogen to microbial protein in particular.

References

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Can Direct Conversion of Used Nitrogen to New Feed and Protein Help Feed the World?
Matassa, Silvio; Batstone, Damien J.; Hulsen, Tim; Schnoor, Jerald; Verstraete, Willy
Environmental Science & Technology (2015), 49 (9), 5247-5254CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
A review. The increase in the world population, vulnerability of conventional crop prodn. to climate change, and population shifts to megacities justify a re-examn. of current methods of converting reactive nitrogen to dinitrogen gas in sewage and waste treatment plants. Indeed, by up-grading treatment plants to factories in which the incoming materials are first deconstructed to units such as ammonia, carbon dioxide and clean minerals, one can implement a highly intensive and efficient microbial resynthesis process in which the used nitrogen is harvested as microbial protein (at efficiencies close to 100%). This can be used for animal feed and food purposes. The technol. for recovery of reactive nitrogen as microbial protein is available but a change of mindset needs to be achieved to make such recovery acceptable.
10
Galloway, J. N. Nitrogen footprints: Past, present and future Environ. Res. Lett. 2014, 9, 115003 DOI: 10.1088/1748-9326/9/11/115003
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Bodirsky, B. L. N2O emissions from the global agricultural nitrogen cycle-current state and future scenarios Biogeosciences 2012, 9, 4169– 4197 DOI: 10.5194/bg-9-4169-2012
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N2O emissions from the global agricultural nitrogen cycle-current state and future scenarios
Bodirsky, B. L.; Popp, A.; Weindl, I.; Dietrich, J. P.; Rolinski, S.; Scheiffele, L.; Schmitz, C.; Lotze-Campen, H.
Biogeosciences (2012), 9 (10), 4169-4197CODEN: BIOGGR; ISSN:1726-4170. (Copernicus Publications)
Reactive nitrogen (Nr) is not only an important nutrient for plant growth, thereby safeguarding human alimentation, but it also heavily disturbs natural systems. To mitigate air, land, aquatic, and atm. pollution caused by the excessive availability of Nr, it is crucial to understand the long-term development of the global agricultural Nr cycle. For our anal., we combine a material flow model with a land-use optimization model. In a first step we est. the state of the Nr cycle in 1995. In a second step we create four scenarios for the 21st century in line with the SRES storylines. Our results indicate that in 1995 only half of the Nr applied to croplands was incorporated into plant biomass. Moreover, less than 10 per cent of all Nr in cropland plant biomass and grazed pasture was consumed by humans. In our scenarios a strong surge of the Nr cycle occurs in the first half of the 21st century, even in the environmentally oriented scenarios. Nitrous oxide (N2O) emissions rise from 3 Tg N2O-N in 1995 to 7-9 in 2045 and 5-12 Tg in 2095. Reinforced Nr pollution mitigation efforts are therefore required.
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Lelieveld, J.; Evans, J. S.; Fnais, M.; Giannadaki, D.; Pozzer, A. The contribution of outdoor air pollution sources to premature mortality on a global scale Nature 2015, 525, 367– 371 DOI: 10.1038/nature15371
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The contribution of outdoor air pollution sources to premature mortality on a global scale
Lelieveld, J.; Evans, J. S.; Fnais, M.; Giannadaki, D.; Pozzer, A.
Nature (London, United Kingdom) (2015), 525 (7569), 367-371CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
Assessing the global burden of disease is based on epidemiol. cohort studies which connect premature mortality to a wide range of causes, including long-term health impacts of O3 and fine particulate matter (PM2.5). It is difficult to quantify premature mortality related to air pollution, notably in regions where air quality is not monitored, and because toxicity of particles from various sources may vary. This work used a global atm. chem. model to assess the link between premature mortality and 7 emission source categories in urban and rural environments. In accord with the global burden of disease for 2010 (S.S. Lim, et al., 2013), the authors calcd. outdoor air pollution, mostly PM2.5, led to 3.3 million (95% confidence interval, 1.61-4.81) premature deaths/yr worldwide, predominantly in Asia. It was primarily assumed that all particles were equally toxic, but a sensitivity study was conducted to account for differential toxicity. Results showed emissions from residential energy use (heating, cooking), prevalent in India and China, had the largest effect on premature mortality globally, even more dominant if carbonaceous particles are assumed to be most toxic. In much of the US and several other countries, traffic and power generation emissions are important. In eastern US, Europe, Russia, and East Asia, agricultural emissions provide the largest relative contribution to PM2.5, with estd. overall health impact dependent on particle toxicity assumptions. Model projections based on a business-as-usual emission scenario indicated the contribution of outdoor air pollution to premature mortality could double by 2050.
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Sustainability. Planetary boundaries: guiding human development on a changing planet
Steffen Will; Richardson Katherine; Rockstrom Johan; Cornell Sarah E; Fetzer Ingo; Bennett Elena M; Biggs Reinette; Carpenter Stephen R; de Vries Wim; de Wit Cynthia A; Folke Carl; Gerten Dieter; Heinke Jens; Mace Georgina M; Persson Linn M; Ramanathan Veerabhadran; Reyers Belinda; Sorlin Sverker
Science (New York, N.Y.) (2015), 347 (6223), 1259855 ISSN:.
The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries--climate change and biosphere integrity--have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.
14
Townsend, A. R. Human health effects of a changing global nitrogen cycle Frontiers in Ecology and the Environment 2003, 1, 240– 246 DOI: 10.1890/1540-9295(2003)001[0240:HHEOAC]2.0.CO;2
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Food Security: The Challenge of Feeding 9 Billion People
Godfray, H. Charles J.; Beddington, John R.; Crute, Ian R.; Haddad, Lawrence; Lawrence, David; Muir, James F.; Pretty, Jules; Robinson, Sherman; Thomas, Sandy M.; Toulmin, Camilla
Science (Washington, DC, United States) (2010), 327 (5967), 812-818CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
Continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years. Growing competition for land, water, and energy, in addn. to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. But the world can produce more food and can ensure that it is used more efficiently and equitably. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security, different components of which are explored here.
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Sutton, M. A.; Bleeker, A. Environmental science: The shape of nitrogen to come Nature 2013, 494, 435– 437 DOI: 10.1038/nature11954
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de Vries, W.; Kros, J.; Kroeze, C.; Seitzinger, S. P. Assessing planetary and regional nitrogen boundaries related to food security and adverse environmental impacts Current Opinion in Environmental Sustainability 2013, 5, 392– 402 DOI: 10.1016/j.cosust.2013.07.004
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Sustainability Your feet's too big
Galloway, James N.; Leach, Allison M.
Nature Geoscience (2016), 9 (2), 97-98CODEN: NGAEBU; ISSN:1752-0894. (Nature Publishing Group)
Humanity's nitrogen pollution footprint has increased by a factor of six since the 1930s. A global anal. reveals that a quarter of this nitrogen pollution is assocd. with the prodn. of internationally traded products.
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Anupama; Ravindra, P. Value-added food: Single cell protein Biotechnol. Adv. 2000, 18, 459– 479 DOI: 10.1016/S0734-9750(00)00045-8
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Value-added food: Single cell protein
Anupama; Ravindra, P.
Biotechnology Advances (2000), 18 (6), 459-479CODEN: BIADDD; ISSN:0734-9750. (Elsevier Science Inc.)
A review with 117 refs. The alarming rate of population growth has increased the demand for food prodn. in third-world countries leading to a yawning gap in demand and supply. This has led to an increase in the no. of hungry and chronically malnourished people. This situation has created a demand for the formulation of innovative and alternative proteinaceous food sources. Single cell protein (SCP) prodn. is a major step in this direction. SCP is the protein extd. from cultivated microbial biomass. It can be used for protein supplementation of a staple diet by replacing costly conventional sources like soymeal and fishmeal to alleviate the problem of protein scarcity. Moreover, bioconversion of agricultural and industrial wastes to protein-rich food and fodder stocks has an addnl. benefit of making the final product cheaper. This would also offset the neg. cost value of wastes used as substrate to yield SCP. Further, it would make food prodn. less dependent upon land and relieve the pressure on agriculture. This article reviews diversified aspects of SCP as an alternative protein-supplementing source. Various potential strains and substrates that could be utilized for SCP prodn. are described. Nutritive value and removal of nucleic acids and toxins from SCP as a protein-supplementing source are discussed. New processes need to be exploited to improve yield. In that direction the solid state fermn. (SSF) method and its advantages for SCP prodn. are highlighted.
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http://www.indexmundi.com/commodities/?commodity=fish-meal&months=300.
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Matassa, S.; Boon, N.; Pikaar, I.; Verstraete, W. Microbial protein: future sustainable food supply route with low environmental footprint Microb. Biotechnol. 2016, 9, 568– 575 DOI: 10.1111/1751-7915.12369
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Microbial protein: future sustainable food supply route with low environmental footprint
Matassa Silvio; Boon Nico; Verstraete Willy; Matassa Silvio; Verstraete Willy; Pikaar Ilje; Verstraete Willy
Microbial biotechnology (2016), 9 (5), 568-75 ISSN:.
Microbial biotechnology has a long history of producing feeds and foods. The key feature of today's market economy is that protein production by conventional agriculture based food supply chains is becoming a major issue in terms of global environmental pollution such as diffuse nutrient and greenhouse gas emissions, land use and water footprint. Time has come to re-assess the current potentials of producing protein-rich feed or food additives in the form of algae, yeasts, fungi and plain bacterial cellular biomass, producible with a lower environmental footprint compared with other plant or animal-based alternatives. A major driver is the need to no longer disintegrate but rather upgrade a variety of low-value organic and inorganic side streams in our current non-cyclic economy. In this context, microbial bioconversions of such valuable matters to nutritive microbial cells and cell components are a powerful asset. The worldwide market of animal protein is of the order of several hundred million tons per year, that of plant protein several billion tons of protein per year; hence, the expansion of the production of microbial protein does not pose disruptive challenges towards the process of the latter. Besides protein as nutritive compounds, also other cellular components such as lipids (single cell oil), polyhydroxybuthyrate, exopolymeric saccharides, carotenoids, ectorines, (pro)vitamins and essential amino acids can be of value for the growing domain of novel nutrition. In order for microbial protein as feed or food to become a major and sustainable alternative, addressing the challenges of creating awareness and achieving public and broader regulatory acceptance are real and need to be addressed with care and expedience.
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Matassa, S.; Verstraete, W.; Pikaar, I.; Boon, N. Autotrophic nitrogen assimilation and carbon capture for microbial protein production by a novel enrichment of hydrogen-oxidizing bacteria Water Res. 2016, 101, 137– 146 DOI: 10.1016/j.watres.2016.05.077
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Autotrophic nitrogen assimilation and carbon capture for microbial protein production by a novel enrichment of hydrogen-oxidizing bacteria
Matassa, Silvio; Verstraete, Willy; Pikaar, Ilje; Boon, Nico
Water Research (2016), 101 (), 137-146CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
Domestic used water treatment systems are currently predominantly based on conventional resource inefficient treatment processes. While resource recovery is gaining momentum it lacks high value end-products which can be efficiently marketed. Microbial protein prodn. offers a valid and promising alternative by upgrading low value recovered resources into high quality feed and also food. In the present study, we evaluated the potential of hydrogen-oxidizing bacteria to upgrade ammonium and carbon dioxide under autotrophic growth conditions. The enrichment of a generic microbial community and the implementation of different culture conditions (sequenced batch resp. continuous reactor) revealed surprising features. At low selection pressure (i.e. under sequenced batch culture at high solid retention time), a very diverse microbiome with an important presence of predatory Bdellovibrio spp. was obsd. The microbial culture which evolved under high rate selection pressure (i.e. diln. rate D = 0.1 h-1) under continuous reactor conditions was dominated by Sulfuricurvum spp. and a highly stable and efficient process in terms of N and C uptake, biomass yield and volumetric productivity was attained. Under continuous culture conditions the max. yield obtained was 0.29 g cell dry wt. per g COD equiv. of hydrogen, whereas the max. volumetric loading rate peaked 0.41 g cell dry wt. per L per h at a protein content of 71%. Finally, the microbial protein produced was of high nutritive quality in terms of essential amino acids content and can be a suitable substitute for conventional feed sources such as fishmeal or soybean meal.
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Matassa, S.; Boon, N.; Verstraete, W. Resource recovery from used water: The manufacturing abilities of hydrogen-oxidizing bacteria Water Res. 2015, 68, 467– 478 DOI: 10.1016/j.watres.2014.10.028
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Resource recovery from used water: The manufacturing abilities of hydrogen-oxidizing bacteria
Matassa, Silvio; Boon, Nico; Verstraete, Willy
Water Research (2015), 68 (), 467-478CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
A review. Resources in used water are at present mainly destroyed rather than reused. Recovered nutrients can serve as raw material for the sustainable prodn. of high value bio-products. The concept of using hydrogen and oxygen, produced by green or off-peak energy by electrolysis, as well as the unique capability of autotrophic hydrogen oxidizing bacteria to upgrade nitrogen and minerals into valuable microbial biomass, is proposed. Both axenic and mixed microbial cultures can thus be of value to implement re-synthesis of recovered nutrients in biomols. This process can become a major line in the sustainable "water factory" of the future.
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Pohlmann, A. Genome sequence of the Bioplastic-producing [ldquo]Knallgas[rdquo] bacterium Ralstonia eutropha H16 Nat. Biotechnol. 2006, 24, 1257– 1262 DOI: 10.1038/nbt1244
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Popp, A. Land-use protection for climate change mitigation Nat. Clim. Change 2014, 4, 1095– 1098 DOI: 10.1038/nclimate2444
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Land-use protection for climate change mitigation
Popp, Alexander; Humpenoeder, Florian; Weindl, Isabelle; Bodirsky, Benjamin Leon; Bonsch, Markus; Lotze-Campen, Hermann; Mueller, Christoph; Biewald, Anne; Rolinski, Susanne; Stevanovic, Miodrag; Dietrich, Jan Philipp
Nature Climate Change (2014), 4 (12), 1095-1098CODEN: NCCACZ; ISSN:1758-6798. (Nature Publishing Group)
Land-use change, mainly the conversion of tropical forests to agricultural land, is a massive source of carbon emissions and contributes substantially to global warming. Therefore, mechanisms that aim to reduce carbon emissions from deforestation are widely discussed. A central challenge is the avoidance of international carbon leakage if forest conservation is not implemented globally. Here, we show that forest conservation schemes, even if implemented globally, could lead to another type of carbon leakage by driving cropland expansion in non-forested areas that are not subject to forest conservation schemes (non-forest leakage). These areas have a smaller, but still considerable potential to store carbon. We show that a global forest policy could reduce carbon emissions by 77 Gt CO2, but would still allow for decreases in carbon stocks of non-forest land by 96 Gt CO2 until 2100 due to non-forest leakage effects. Furthermore, abandonment of agricultural land and assocd. carbon uptake through vegetation regrowth is hampered. Effective mitigation measures thus require financing structures and conservation investments that cover the full range of carbon-rich ecosystems. However, our anal. indicates that greater agricultural productivity increases would be needed to compensate for such restrictions on agricultural expansion.
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Foley, Jonathan A.; Ramankutty, Navin; Brauman, Kate A.; Cassidy, Emily S.; Gerber, James S.; Johnston, Matt; Mueller, Nathaniel D.; O'Connell, Christine; Ray, Deepak K.; West, Paul C.; Balzer, Christian; Bennett, Elena M.; Carpenter, Stephen R.; Hill, Jason; Monfreda, Chad; Polasky, Stephen; Rockstroem, Johan; Sheehan, John; Siebert, Stefan; Tilman, David; Zaks, David P. M.
Nature (London, United Kingdom) (2011), 478 (7369), 337-342CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approx. a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainability needs, food prodn. must grow substantially while, at the same time, agriculture's environmental footprint must shrink dramatically. Here we analyze solns. to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food prodn. while greatly reducing the environmental impacts of agriculture.
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Stehle, S.; Schulz, R. Agricultural insecticides threaten surface waters at the global scale Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 5750 DOI: 10.1073/pnas.1500232112
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Stehle, Sebastian; Schulz, Ralf
Proceedings of the National Academy of Sciences of the United States of America (2015), 112 (18), 5750-5755CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
Compared with nutrient levels and habitat degrdn., the importance of agricultural pesticides in surface water may have been underestimated due to a lack of comprehensive quant. anal. Increasing pesticide contamination results in decreasing regional aquatic biodiversity, i.e., macroinvertebrate family richness is reduced by ∼30% at pesticide concns. equaling the legally accepted regulatory threshold levels (RTLs). This study provides a comprehensive meta anal. of 838 peer-reviewed studies (>2,500 sites in 73 countries) that evaluates, for the first time to our knowledge on a global scale, the exposure of surface waters to particularly toxic agricultural insecticides. We tested whether measured insecticide concns. (MICs; i.e., quantified insecticide concns.) exceed their RTLs and how risks depend on insecticide development over time and stringency of environmental regulation. Our anal. reveals that MICs occur rarely (i.e., an estd. 97.4% of analyses conducted found no MICs) and there is a complete lack of scientific monitoring data for ∼90% of global cropland. Most importantly, of the 11,300 MICs, 52.4% (5,915 cases; 68.5% of the sites) exceeded the RTL for either surface water (RTLSW) or sediments. Thus, the biol. integrity of global water resources is at a substantial risk. RTLSW exceedances depend on the catchment size, sampling regime, and sampling date; are significantly higher for newer-generation insecticides (i.e., pyrethroids); and are high even in countries with stringent environmental regulations. These results suggest the need for worldwide improvements to current pesticide regulations and agricultural pesticide application practices and for intensified research efforts on the presence and effects of pesticides under real-world conditions.
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The Challenge of Micropollutants in Aquatic Systems
Schwarzenbach, Rene P.; Escher, Beate I.; Fenner, Kathrin; Hofstetter, Thomas B.; Johnson, C. Annette; von Gunten, Urs; Wehrli, Bernhard
Science (Washington, DC, United States) (2006), 313 (5790), 1072-1077CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
A review. Increasing worldwide freshwater system pollution by industrial and natural chem. compds. is a key environmental problem. Although most compds. occur in low concns., many have considerable toxicol. concerns, particularly when present as components of complex mixts. This review assesses 3 scientific challenges in addressing water quality problems caused by such micro-pollutants. Tools to assess the impact of these pollutants on aquatic life and human health must be further developed and refined. Cost-effective, appropriate remediation and water treatment technologies must be explored and implemented. Use and disposal strategies coupled with the search for environmentally more benign products and processes should minimize introduction of crit. pollutants to the aquatic environment. Topics discussed include: micro-pollutant assessment in aquatic systems; mitigating aq. micro-pollutants; water quality preventive management; and outlook.
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Verstraete Willy
Microbial biotechnology (2015), 8 (1), 36-7 ISSN:.
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van der Lelie Daniel; Taghavi Safiyh; Henry Christopher; Gilbert Jack A; Henry Christopher; Henry Christopher; Gilbert Jack A; Gilbert Jack A
Microbial biotechnology (2017), 10 (1), 4-5 ISSN:.
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Fox, A. R. Major cereal crops benefit from biological nitrogen fixation when inoculated with the nitrogen-fixing bacterium Pseudomonas protegens Pf-5 X940 Environ. Microbiol. 2016, 18, 3522– 3534 DOI: 10.1111/1462-2920.13376
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Major cereal crops benefit from biological nitrogen fixation when inoculated with the nitrogen-fixing bacterium Pseudomonas protegens Pf-5 X940
Fox, Ana Romina; Soto, Gabriela; Valverde, Claudio; Russo, Daniela; Lagares, Antonio, Jr; Zorreguieta, Angeles; Alleva, Karina; Pascuan, Cecilia; Frare, Romina; Mercado-Blanco, Jesus; Dixon, Ray; Ayub, Nicolas Daniel
Environmental Microbiology (2016), 18 (10), 3522-3534CODEN: ENMIFM; ISSN:1462-2912. (Wiley-Blackwell)
Summary : A main goal of biol. nitrogen fixation research has been to expand the nitrogen-fixing ability to major cereal crops. In this work, we demonstrate the use of the efficient nitrogen-fixing rhizobacterium Pseudomonas protegens Pf-5 X940 as a chassis to engineer the transfer of nitrogen fixed by BNF to maize and wheat under non-gnotobiotic conditions. Inoculation of maize and wheat with Pf-5 X940 largely improved nitrogen content and biomass accumulation in both vegetative and reproductive tissues, and this beneficial effect was pos. assocd. with high nitrogen fixation rates in roots. 15N isotope diln. anal. showed that maize and wheat plants obtained substantial amts. of fixed nitrogen from the atm. Pf-5 X940-GFP-tagged cells were always reisolated from the maize and wheat root surface but never from the inner root tissues. Confocal laser scanning microscopy confirmed root surface colonization of Pf-5 X940-GFP in wheat plants, and microcolonies were mostly visualized at the junctions between epidermal root cells. Genetic anal. using biofilm formation-related Pseudomonas mutants confirmed the relevance of bacterial root adhesion in the increase in nitrogen content, biomass accumulation and nitrogen fixation rates in wheat roots. To our knowledge, this is the first report of robust BNF in major cereal crops.
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Electrochemical Society Interface (2015), 24 (2), 51-57CODEN: ELSIE3; ISSN:1064-8208. (Electrochemical Society)
A review. The approach of electrochem. synthesis of ammonia at low pressure and low temp.
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Brown, K. A. Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid Science 2016, 352, 448– 450 DOI: 10.1126/science.aaf2091
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Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid
Brown, Katherine A.; Harris, Derek F.; Wilker, Molly B.; Rasmussen, Andrew; Khadka, Nimesh; Hamby, Hayden; Keable, Stephen; Dukovic, Gordana; Peters, John W.; Seefeldt, Lance C.; King, Paul W.
Science (Washington, DC, United States) (2016), 352 (6284), 448-450CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
Nitrogenase enzymes catalyze the biol. prodn. of fixed nitrogen. Because this is not enough to sustain modern agriculture, industrial fertilizers contg. ammonia are produced via the energy-intensive Haber-Bosch process. Brown et al. developed a way to use nitrogenase enzymes from nitrogen-fixing bacteria to make ammonia in vitro without other biol. steps or high-energy inputs. Light-activated CdS nanorods provided electrons to the FeMo nitrogenase enzyme to reduce nitrogen and produce ammonia at rates up to 64% of biol. nitrogen fixation. These nanoparticle-protein complexes show the potential for solar-driven ammonia prodn. Science, this issue p. 448.
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Environmental Science & Technology (2012), 46 (17), 9420-9427CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
Human activity has intensely altered the global N cycle, producing nitrogenous gases of environmental significance, particularly in China where the most serious worldwide atm. N pollution exists. This work comprehensively assessed NH3, NOx, and N2O emissions in China based on a full cycle anal. Total reactive nitrogen (Nr) emissions more than doubled over the past 30 yr, during which the increasing trend slowed for NH3 emissions after 2000, while the increasing trend continued to accelerate for NOx and N2O emissions. Several hot-spots were identified; their Nr emissions were ∼10 times higher than others. Agricultural sources caused 95% of total NH3 emissions; fossil fuel combustion accounted for 96% of total NOx emissions; and agricultural (51%) and natural sources (forest, surface water, 39%) both contributed to Chinese N2O emissions. Total atm. Nr emission-related health damage in China (2008) reached 19-62 billion US dollars, accounting for 0.4-1.4% of its gross domestic product, of which 52-60% was from NH3 emissions and 39-47% was from NOx emissions. These results provide policy-makers an integrated view of Nr sources and health damage to address significant challenges assocd. with reduced air pollution.
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Environmental Science & Technology (2013), 47 (8), 3571-3579CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
Cost-benefit anal. can be used to provide guidance for emerging policy priorities in reducing nitrogen (N) pollution. This paper provides a crit. and comprehensive assessment of costs and benefits of the various flows of N on human health, ecosystems and climate stability to identify major options for mitigation. The social cost of impacts of N in the EU27 in 2008 was estd. between euro75-485 billion per yr. A cost share of around 60% is related to emissions to air. The share of total impacts on human health is ∼45% and may reflect the higher willingness to pay for human health than for ecosystems or climate stability. Air pollution by nitrogen also generates social benefits for climate by present cooling effects of N contg. aerosol and C-sequestration driven by N deposition, amounting to an estd. net benefit of about euro5 billion/yr. The economic benefit of N in primary agricultural prodn. ranges between euro20-80 billion/yr and is lower than the annual cost of pollution by agricultural N which is in the range of euro35-230 billion/yr. Internalizing these environmental costs would lower the optimum annual N-fertilization rate in Northwestern Europe by ∼50 kg/ha. Acknowledging the large uncertainties and conceptual issues of our cost-benefit ests., the results support the priority for further redn. of NH3 and NOx emissions from transport and agriculture beyond commitments recently agreed in revision of the Gothenburg Protocol.
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Leakage of reactive nitrogen (N) from human activities to the environment can cause human health and ecol. problems. Often these harmful effects are not reflected in the costs of food, fuel, and fiber that derive from N use. Spatial analyses of damage costs attributable to source at management relevant scales could inform decisions in areas where anthropogenic N leakage causes harm. We used recently compiled data describing N inputs in the conterminous United States (US) to assess potential damage costs assocd. with anthropogenic N. We estd. fates of N leaked to the environment (air/deposition, surface freshwater, groundwater, and coastal zones) in the early 2000s by multiplying watershed-level N inputs (8-digit US Geol. Survey Hydrol. Unit Codes; HUC8s) with published coeffs. describing nutrient uptake efficiency, leaching losses, and gaseous emissions. We scaled these N leakage ests. with mitigation, remediation, direct damage, and substitution costs assocd. with human health, agriculture, ecosystems, and climate (per kg of N) to calc. annual damage cost (US dollars in 2008 or as reported) of anthropogenic N per HUC8. Ests. of N leakage byHUC8 ranged from <1 to 125 kg N ha-1 yr-1, with most N leaked to freshwater ecosystems. Ests. of potential damages (based on median ests.) ranged from $1.94 to $2255 ha-1 yr-1 across watersheds, with a median of $252 ha-1 yr-1. Eutrophication of freshwater ecosystems and respiratory effects of atm. N pollution were important across HUC8s. However, significant data gaps remain in our ability to fully assess N damages, such as damage costs from harmful algal blooms and drinking water contamination. Nationally, potential health and environmental damages of anthropogenic N in the early 2000s totaled $210 billion yr-1 USD (range: $81-$441 billion yr-1). While a no. of gaps and uncertainties remain in these ests., overall this work represents a starting point to inform decisions and engage stakeholders on the costs of N pollution.
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Philosophical Transactions of the Royal Society, B: Biological Sciences (2013), 368 (1621), 20130116/1-20130116/9CODEN: PTRBAE; ISSN:0962-8436. (Royal Society)
The demand for more food is increasing fertilizer and land use, and the demand for more energy is increasing fossil fuel combustion, leading to enhanced losses of reactive nitrogen (Nr) to the environment. Many thresholds for human and ecosystem health have been exceeded owing to Nr pollution, including those for drinking water (nitrates), air quality (smog, particulate matter, ground-level ozone), freshwater eutrophication, biodiversity loss, stratospheric ozone depletion, climate change and coastal ecosystems (dead zones). Each of these environmental effects can be magnified by the 'nitrogen cascade': a single atom of Nr can trigger a cascade of neg. environmental impacts in sequence. Here, we provide an overview of the impact of Nr on the environment and human health, including an assessment of the magnitude of different environmental problems, and the relative importance of Nr as a contributor to each problem. In some cases, Nr loss to the environment is the key driver of effects (e.g. terrestrial and coastal eutrophication, nitrous oxide emissions), whereas in some other situations nitrogen represents a key contributor exacerbating a wider problem (e.g. freshwater pollution, biodiversity loss). In this way, the central role of nitrogen can remain hidden, even though it actually underpins many trans-boundary pollution problems.
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Ecosystem services altered by human changes in the nitrogen cycle: a new perspective for US decision making
Compton Jana E; Harrison John A; Dennis Robin L; Greaver Tara L; Hill Brian H; Jordan Stephen J; Walker Henry; Campbell Holly V
Ecology letters (2011), 14 (8), 804-15 ISSN:.
Human alteration of the nitrogen (N) cycle has produced benefits for health and well-being, but excess N has altered many ecosystems and degraded air and water quality. US regulations mandate protection of the environment in terms that directly connect to ecosystem services. Here, we review the science quantifying effects of N on key ecosystem services, and compare the costs of N-related impacts or mitigation using the metric of cost per unit of N. Damage costs to the provision of clean air, reflected by impaired human respiratory health, are well characterized and fairly high (e.g. costs of ozone and particulate damages of $28 per kg NO(x)-N). Damage to services associated with productivity, biodiversity, recreation and clean water are less certain and although generally lower, these costs are quite variable (<$2.2-56 per kg N). In the current Chesapeake Bay restoration effort, for example, the collection of available damage costs clearly exceeds the projected abatement costs to reduce N loads to the Bay ($8-15 per kg N). Explicit consideration and accounting of effects on multiple ecosystem services provides decision-makers an integrated view of N sources, damages and abatement costs to address the significant challenges associated with reducing N pollution.
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Birch, M. B. L.; Gramig, B. M.; Moomaw, W. R.; Doering, O. C., III; Reeling, C. J. Why Metrics Matter: Evaluating Policy Choices for Reactive Nitrogen in the Chesapeake Bay Watershed Environ. Sci. Technol. 2011, 45, 168– 174 DOI: 10.1021/es101472z
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Why Metrics Matter: Evaluating Policy Choices for Reactive Nitrogen in the Chesapeake Bay Watershed
Birch, Melissa B. L.; Gramig, Benjamin M.; Moomaw, William R.; Doering, Otto C., III; Reeling, Carson J.
Environmental Science & Technology (2011), 45 (1), 168-174CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
Despite major efforts, the redn. of reactive N (rN) using traditional metrics and policy tools for the Chesapeake Bay has slowed in recent years. We apply the concept of the N Cascade to the chem. dynamic nature and multiple sources of rN to examine the temporal and spatial movement of different forms of rN through multiple ecosystems and media. We also demonstrate the benefit of using more than the traditional mass fluxes to set criteria for action. The use of multiple metrics provides addnl. information about where the most effective intervention point might be. Utilizing damage costs or mortality metrics demonstrates that even though the mass fluxes to the atm. are lower than direct releases to terrestrial and aquatic ecosystems, total damage costs to all ecosystems and health are higher because of the cascade of rN and the assocd. damages, and because they exact a higher human health cost. Abatement costs for reducing rN releases into the air are also lower. These findings have major implications for the use of multiple metrics and the addnl. benefits of expanding the scope of concern beyond the bay itself and support improved coordination between the Clean Air and Clean Water Acts while restoring the Chesapeake Bay.
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Cite this: Environ. Sci. Technol. 2017, 51, 13, 7297–7303

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Abstract
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Figure 1
Figure 1. Amount of Haber Bosch nitrogen required and its fate during the different protein production routes. The orange and green fractions represent the amount of reactive nitrogen lost or retained, respectively, within the protein supply chain (expressed in percentage of total input, i.e., 100%). The vegetarian- and animal-product-based protein supply routes are adapted from ref 52. A nitrogen uptake efficiency in the microbial protein production step of 90% was assumed; all other losses were based on Galloway and Cowling. (52)
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Figure 2
Figure 2. Currently available mitigation measures may not have the capacity to decrease nitrogen losses sufficiently. (3) The scenarios described in the figure are (a) a middle-of-the road scenario of the shared socio-economic pathways, (53) (b) reduction to a maximum of 20% in household waste with increased waste recycling, (c) animal consumption reduced to 50% of western diets, (d) improved fertilization, (e) improved livestock management, and (f) with all mitigation measures in combination. Panels g–i describe a range for critical thresholds for reactive nitrogen related greenhouse gases, air pollution, and water pollution, respectively. Please refer to Bodirsky et al. (2014) (3) for a detailed description of all the mitigation methods, simulated reactive nitrogen flows, and critical thresholds.
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Figure 3
Figure 3. Potential technological pathways for industrial-reactor-based production of MP using different feedstocks with their respective inputs and environmental losses for livestock production and human consumption. Direct upgrading of Haber Bosch generated reactive nitrogen into microbial proteins using hydrogen, methane, or carbohydrates as energy source for microbial growth. Green and gray arrows represent inputs, whereas red arrows represent losses to water, atmosphere, and soil.
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References
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  Bodirsky, B. L.; Popp, A.; Weindl, I.; Dietrich, J. P.; Rolinski, S.; Scheiffele, L.; Schmitz, C.; Lotze-Campen, H.
  Biogeosciences (2012), 9 (10), 4169-4197CODEN: BIOGGR; ISSN:1726-4170. (Copernicus Publications)
  Reactive nitrogen (Nr) is not only an important nutrient for plant growth, thereby safeguarding human alimentation, but it also heavily disturbs natural systems. To mitigate air, land, aquatic, and atm. pollution caused by the excessive availability of Nr, it is crucial to understand the long-term development of the global agricultural Nr cycle. For our anal., we combine a material flow model with a land-use optimization model. In a first step we est. the state of the Nr cycle in 1995. In a second step we create four scenarios for the 21st century in line with the SRES storylines. Our results indicate that in 1995 only half of the Nr applied to croplands was incorporated into plant biomass. Moreover, less than 10 per cent of all Nr in cropland plant biomass and grazed pasture was consumed by humans. In our scenarios a strong surge of the Nr cycle occurs in the first half of the 21st century, even in the environmentally oriented scenarios. Nitrous oxide (N2O) emissions rise from 3 Tg N2O-N in 1995 to 7-9 in 2045 and 5-12 Tg in 2095. Reinforced Nr pollution mitigation efforts are therefore required.
12. 12
  Lelieveld, J.; Evans, J. S.; Fnais, M.; Giannadaki, D.; Pozzer, A. The contribution of outdoor air pollution sources to premature mortality on a global scale Nature 2015, 525, 367– 371 DOI: 10.1038/nature15371
  12
  The contribution of outdoor air pollution sources to premature mortality on a global scale
  Lelieveld, J.; Evans, J. S.; Fnais, M.; Giannadaki, D.; Pozzer, A.
  Nature (London, United Kingdom) (2015), 525 (7569), 367-371CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
  Assessing the global burden of disease is based on epidemiol. cohort studies which connect premature mortality to a wide range of causes, including long-term health impacts of O3 and fine particulate matter (PM2.5). It is difficult to quantify premature mortality related to air pollution, notably in regions where air quality is not monitored, and because toxicity of particles from various sources may vary. This work used a global atm. chem. model to assess the link between premature mortality and 7 emission source categories in urban and rural environments. In accord with the global burden of disease for 2010 (S.S. Lim, et al., 2013), the authors calcd. outdoor air pollution, mostly PM2.5, led to 3.3 million (95% confidence interval, 1.61-4.81) premature deaths/yr worldwide, predominantly in Asia. It was primarily assumed that all particles were equally toxic, but a sensitivity study was conducted to account for differential toxicity. Results showed emissions from residential energy use (heating, cooking), prevalent in India and China, had the largest effect on premature mortality globally, even more dominant if carbonaceous particles are assumed to be most toxic. In much of the US and several other countries, traffic and power generation emissions are important. In eastern US, Europe, Russia, and East Asia, agricultural emissions provide the largest relative contribution to PM2.5, with estd. overall health impact dependent on particle toxicity assumptions. Model projections based on a business-as-usual emission scenario indicated the contribution of outdoor air pollution to premature mortality could double by 2050.
13. 13
  Steffen, W. Planetary boundaries: Guiding human development on a changing planet Science 2015, 347, 1259855 DOI: 10.1126/science.1259855
  13
  Sustainability. Planetary boundaries: guiding human development on a changing planet
  Steffen Will; Richardson Katherine; Rockstrom Johan; Cornell Sarah E; Fetzer Ingo; Bennett Elena M; Biggs Reinette; Carpenter Stephen R; de Vries Wim; de Wit Cynthia A; Folke Carl; Gerten Dieter; Heinke Jens; Mace Georgina M; Persson Linn M; Ramanathan Veerabhadran; Reyers Belinda; Sorlin Sverker
  Science (New York, N.Y.) (2015), 347 (6223), 1259855 ISSN:.
  The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries--climate change and biosphere integrity--have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.
14. 14
  Townsend, A. R. Human health effects of a changing global nitrogen cycle Frontiers in Ecology and the Environment 2003, 1, 240– 246 DOI: 10.1890/1540-9295(2003)001[0240:HHEOAC]2.0.CO;2
  There is no corresponding record for this reference.
15. 15
  United Nations Population Division. The World Population Prospects; Department of Economic and Social Affairs, The United Nations: New York, 2015.
  There is no corresponding record for this reference.
16. 16
  Bodirsky, B. L. Global food demand scenarios for the 21st century PLoS One 2015, 10, e0139201 DOI: 10.1371/journal.pone.0139201
  There is no corresponding record for this reference.
17. 17
  Godfray, H. C. J. Food Security: The Challenge of Feeding 9 Billion People Science 2010, 327, 812– 818 DOI: 10.1126/science.1185383
  17
  Food Security: The Challenge of Feeding 9 Billion People
  Godfray, H. Charles J.; Beddington, John R.; Crute, Ian R.; Haddad, Lawrence; Lawrence, David; Muir, James F.; Pretty, Jules; Robinson, Sherman; Thomas, Sandy M.; Toulmin, Camilla
  Science (Washington, DC, United States) (2010), 327 (5967), 812-818CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
  Continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years. Growing competition for land, water, and energy, in addn. to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. But the world can produce more food and can ensure that it is used more efficiently and equitably. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security, different components of which are explored here.
18. 18
  Sutton, M. A.; Bleeker, A. Environmental science: The shape of nitrogen to come Nature 2013, 494, 435– 437 DOI: 10.1038/nature11954
  There is no corresponding record for this reference.
19. 19
  Sutton, M.A. Our Nutrient World: The Challenge to Produce More Food and Energy with Less Pollution; Centre for Ecology & Hydrology on behalf of the Global Partnership on Nutrient Management (GPNM) and the International Nitrogen Initiative (INI), 2013.
  There is no corresponding record for this reference.
20. 20
  Herrero, M. Greenhouse gas mitigation potentials in the livestock sector Nat. Clim. Change 2016, 6, 452– 461 DOI: 10.1038/nclimate2925
  There is no corresponding record for this reference.
21. 21
  de Vries, W.; Kros, J.; Kroeze, C.; Seitzinger, S. P. Assessing planetary and regional nitrogen boundaries related to food security and adverse environmental impacts Current Opinion in Environmental Sustainability 2013, 5, 392– 402 DOI: 10.1016/j.cosust.2013.07.004
  There is no corresponding record for this reference.
22. 22
  Seitzinger, S. Nitrogen cycle: Out of reach Nature 2008, 452, 162– 163 DOI: 10.1038/452162a
  There is no corresponding record for this reference.
23. 23
  Galloway, J. N.; Leach, A. M. Sustainability: Your feet’s too big Nat. Geosci. 2016, 9, 97– 98 DOI: 10.1038/ngeo2647
  23
  Sustainability Your feet's too big
  Galloway, James N.; Leach, Allison M.
  Nature Geoscience (2016), 9 (2), 97-98CODEN: NGAEBU; ISSN:1752-0894. (Nature Publishing Group)
  Humanity's nitrogen pollution footprint has increased by a factor of six since the 1930s. A global anal. reveals that a quarter of this nitrogen pollution is assocd. with the prodn. of internationally traded products.
24. 24
  Anupama; Ravindra, P. Value-added food: Single cell protein Biotechnol. Adv. 2000, 18, 459– 479 DOI: 10.1016/S0734-9750(00)00045-8
  24
  Value-added food: Single cell protein
  Anupama; Ravindra, P.
  Biotechnology Advances (2000), 18 (6), 459-479CODEN: BIADDD; ISSN:0734-9750. (Elsevier Science Inc.)
  A review with 117 refs. The alarming rate of population growth has increased the demand for food prodn. in third-world countries leading to a yawning gap in demand and supply. This has led to an increase in the no. of hungry and chronically malnourished people. This situation has created a demand for the formulation of innovative and alternative proteinaceous food sources. Single cell protein (SCP) prodn. is a major step in this direction. SCP is the protein extd. from cultivated microbial biomass. It can be used for protein supplementation of a staple diet by replacing costly conventional sources like soymeal and fishmeal to alleviate the problem of protein scarcity. Moreover, bioconversion of agricultural and industrial wastes to protein-rich food and fodder stocks has an addnl. benefit of making the final product cheaper. This would also offset the neg. cost value of wastes used as substrate to yield SCP. Further, it would make food prodn. less dependent upon land and relieve the pressure on agriculture. This article reviews diversified aspects of SCP as an alternative protein-supplementing source. Various potential strains and substrates that could be utilized for SCP prodn. are described. Nutritive value and removal of nucleic acids and toxins from SCP as a protein-supplementing source are discussed. New processes need to be exploited to improve yield. In that direction the solid state fermn. (SSF) method and its advantages for SCP prodn. are highlighted.
25. 25
  Goldberg, I. Single Cell Protein; Springer-Verlag: Springer-Verlag, Berlin, 1985; Vol. 1.
  There is no corresponding record for this reference.
26. 26
  http://www.indexmundi.com/commodities/?commodity=fish-meal&months=300.
  There is no corresponding record for this reference.
27. 27
  Matassa, S.; Boon, N.; Pikaar, I.; Verstraete, W. Microbial protein: future sustainable food supply route with low environmental footprint Microb. Biotechnol. 2016, 9, 568– 575 DOI: 10.1111/1751-7915.12369
  27
  Microbial protein: future sustainable food supply route with low environmental footprint
  Matassa Silvio; Boon Nico; Verstraete Willy; Matassa Silvio; Verstraete Willy; Pikaar Ilje; Verstraete Willy
  Microbial biotechnology (2016), 9 (5), 568-75 ISSN:.
  Microbial biotechnology has a long history of producing feeds and foods. The key feature of today's market economy is that protein production by conventional agriculture based food supply chains is becoming a major issue in terms of global environmental pollution such as diffuse nutrient and greenhouse gas emissions, land use and water footprint. Time has come to re-assess the current potentials of producing protein-rich feed or food additives in the form of algae, yeasts, fungi and plain bacterial cellular biomass, producible with a lower environmental footprint compared with other plant or animal-based alternatives. A major driver is the need to no longer disintegrate but rather upgrade a variety of low-value organic and inorganic side streams in our current non-cyclic economy. In this context, microbial bioconversions of such valuable matters to nutritive microbial cells and cell components are a powerful asset. The worldwide market of animal protein is of the order of several hundred million tons per year, that of plant protein several billion tons of protein per year; hence, the expansion of the production of microbial protein does not pose disruptive challenges towards the process of the latter. Besides protein as nutritive compounds, also other cellular components such as lipids (single cell oil), polyhydroxybuthyrate, exopolymeric saccharides, carotenoids, ectorines, (pro)vitamins and essential amino acids can be of value for the growing domain of novel nutrition. In order for microbial protein as feed or food to become a major and sustainable alternative, addressing the challenges of creating awareness and achieving public and broader regulatory acceptance are real and need to be addressed with care and expedience.
28. 28
  Matassa, S.; Verstraete, W.; Pikaar, I.; Boon, N. Autotrophic nitrogen assimilation and carbon capture for microbial protein production by a novel enrichment of hydrogen-oxidizing bacteria Water Res. 2016, 101, 137– 146 DOI: 10.1016/j.watres.2016.05.077
  28
  Autotrophic nitrogen assimilation and carbon capture for microbial protein production by a novel enrichment of hydrogen-oxidizing bacteria
  Matassa, Silvio; Verstraete, Willy; Pikaar, Ilje; Boon, Nico
  Water Research (2016), 101 (), 137-146CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
  Domestic used water treatment systems are currently predominantly based on conventional resource inefficient treatment processes. While resource recovery is gaining momentum it lacks high value end-products which can be efficiently marketed. Microbial protein prodn. offers a valid and promising alternative by upgrading low value recovered resources into high quality feed and also food. In the present study, we evaluated the potential of hydrogen-oxidizing bacteria to upgrade ammonium and carbon dioxide under autotrophic growth conditions. The enrichment of a generic microbial community and the implementation of different culture conditions (sequenced batch resp. continuous reactor) revealed surprising features. At low selection pressure (i.e. under sequenced batch culture at high solid retention time), a very diverse microbiome with an important presence of predatory Bdellovibrio spp. was obsd. The microbial culture which evolved under high rate selection pressure (i.e. diln. rate D = 0.1 h-1) under continuous reactor conditions was dominated by Sulfuricurvum spp. and a highly stable and efficient process in terms of N and C uptake, biomass yield and volumetric productivity was attained. Under continuous culture conditions the max. yield obtained was 0.29 g cell dry wt. per g COD equiv. of hydrogen, whereas the max. volumetric loading rate peaked 0.41 g cell dry wt. per L per h at a protein content of 71%. Finally, the microbial protein produced was of high nutritive quality in terms of essential amino acids content and can be a suitable substitute for conventional feed sources such as fishmeal or soybean meal.
29. 29
  Matassa, S.; Boon, N.; Verstraete, W. Resource recovery from used water: The manufacturing abilities of hydrogen-oxidizing bacteria Water Res. 2015, 68, 467– 478 DOI: 10.1016/j.watres.2014.10.028
  29
  Resource recovery from used water: The manufacturing abilities of hydrogen-oxidizing bacteria
  Matassa, Silvio; Boon, Nico; Verstraete, Willy
  Water Research (2015), 68 (), 467-478CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)
  A review. Resources in used water are at present mainly destroyed rather than reused. Recovered nutrients can serve as raw material for the sustainable prodn. of high value bio-products. The concept of using hydrogen and oxygen, produced by green or off-peak energy by electrolysis, as well as the unique capability of autotrophic hydrogen oxidizing bacteria to upgrade nitrogen and minerals into valuable microbial biomass, is proposed. Both axenic and mixed microbial cultures can thus be of value to implement re-synthesis of recovered nutrients in biomols. This process can become a major line in the sustainable "water factory" of the future.
30. 30
  Pohlmann, A. Genome sequence of the Bioplastic-producing [ldquo]Knallgas[rdquo] bacterium Ralstonia eutropha H16 Nat. Biotechnol. 2006, 24, 1257– 1262 DOI: 10.1038/nbt1244
  There is no corresponding record for this reference.
31. 31
  Popp, A. Land-use protection for climate change mitigation Nat. Clim. Change 2014, 4, 1095– 1098 DOI: 10.1038/nclimate2444
  31
  Land-use protection for climate change mitigation
  Popp, Alexander; Humpenoeder, Florian; Weindl, Isabelle; Bodirsky, Benjamin Leon; Bonsch, Markus; Lotze-Campen, Hermann; Mueller, Christoph; Biewald, Anne; Rolinski, Susanne; Stevanovic, Miodrag; Dietrich, Jan Philipp
  Nature Climate Change (2014), 4 (12), 1095-1098CODEN: NCCACZ; ISSN:1758-6798. (Nature Publishing Group)
  Land-use change, mainly the conversion of tropical forests to agricultural land, is a massive source of carbon emissions and contributes substantially to global warming. Therefore, mechanisms that aim to reduce carbon emissions from deforestation are widely discussed. A central challenge is the avoidance of international carbon leakage if forest conservation is not implemented globally. Here, we show that forest conservation schemes, even if implemented globally, could lead to another type of carbon leakage by driving cropland expansion in non-forested areas that are not subject to forest conservation schemes (non-forest leakage). These areas have a smaller, but still considerable potential to store carbon. We show that a global forest policy could reduce carbon emissions by 77 Gt CO2, but would still allow for decreases in carbon stocks of non-forest land by 96 Gt CO2 until 2100 due to non-forest leakage effects. Furthermore, abandonment of agricultural land and assocd. carbon uptake through vegetation regrowth is hampered. Effective mitigation measures thus require financing structures and conservation investments that cover the full range of carbon-rich ecosystems. However, our anal. indicates that greater agricultural productivity increases would be needed to compensate for such restrictions on agricultural expansion.
32. 32
  Intergovernmental Panel on Climate Change. Carbon Dioxide Capture and Storage; Cambridge University Press: New York, 2005.
  There is no corresponding record for this reference.
33. 33
  FAOSTAT; Food and Agriculture Organization of the United Nations: Rome, 2012.
  There is no corresponding record for this reference.
34. 34
  Ellis, E. C.; Klein Goldewijk, K.; Siebert, S.; Lightman, D.; Ramankutty, N. Anthropogenic transformation of the biomes, 1700 to 2000 Global Ecology and Biogeography 2010, 19, 589– 606 DOI: 10.1111/j.1466-8238.2010.00540.x
  There is no corresponding record for this reference.
35. 35
  Gibbs, H. K. Brazil’s Soy Moratorium: Supply-chain governance is needed to avoid deforestation Science 2015, 347, 377– 378 DOI: 10.1126/science.aaa0181
  There is no corresponding record for this reference.
36. 36
  Foley, J. A. Solutions for a cultivated planet Nature 2011, 478, 337– 342 DOI: 10.1038/nature10452
  36
  Solutions for a cultivated planet
  Foley, Jonathan A.; Ramankutty, Navin; Brauman, Kate A.; Cassidy, Emily S.; Gerber, James S.; Johnston, Matt; Mueller, Nathaniel D.; O'Connell, Christine; Ray, Deepak K.; West, Paul C.; Balzer, Christian; Bennett, Elena M.; Carpenter, Stephen R.; Hill, Jason; Monfreda, Chad; Polasky, Stephen; Rockstroem, Johan; Sheehan, John; Siebert, Stefan; Tilman, David; Zaks, David P. M.
  Nature (London, United Kingdom) (2011), 478 (7369), 337-342CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
  Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approx. a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainability needs, food prodn. must grow substantially while, at the same time, agriculture's environmental footprint must shrink dramatically. Here we analyze solns. to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food prodn. while greatly reducing the environmental impacts of agriculture.
37. 37
  http://waterfootprint.org/en/water-footprint/product-water-footprint/water-footprint-crop-and-animal-products/.
  There is no corresponding record for this reference.
38. 38
  Stehle, S.; Schulz, R. Agricultural insecticides threaten surface waters at the global scale Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 5750 DOI: 10.1073/pnas.1500232112
  38
  Agricultural insecticides threaten surface waters at the global scale
  Stehle, Sebastian; Schulz, Ralf
  Proceedings of the National Academy of Sciences of the United States of America (2015), 112 (18), 5750-5755CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
  Compared with nutrient levels and habitat degrdn., the importance of agricultural pesticides in surface water may have been underestimated due to a lack of comprehensive quant. anal. Increasing pesticide contamination results in decreasing regional aquatic biodiversity, i.e., macroinvertebrate family richness is reduced by ∼30% at pesticide concns. equaling the legally accepted regulatory threshold levels (RTLs). This study provides a comprehensive meta anal. of 838 peer-reviewed studies (>2,500 sites in 73 countries) that evaluates, for the first time to our knowledge on a global scale, the exposure of surface waters to particularly toxic agricultural insecticides. We tested whether measured insecticide concns. (MICs; i.e., quantified insecticide concns.) exceed their RTLs and how risks depend on insecticide development over time and stringency of environmental regulation. Our anal. reveals that MICs occur rarely (i.e., an estd. 97.4% of analyses conducted found no MICs) and there is a complete lack of scientific monitoring data for ∼90% of global cropland. Most importantly, of the 11,300 MICs, 52.4% (5,915 cases; 68.5% of the sites) exceeded the RTL for either surface water (RTLSW) or sediments. Thus, the biol. integrity of global water resources is at a substantial risk. RTLSW exceedances depend on the catchment size, sampling regime, and sampling date; are significantly higher for newer-generation insecticides (i.e., pyrethroids); and are high even in countries with stringent environmental regulations. These results suggest the need for worldwide improvements to current pesticide regulations and agricultural pesticide application practices and for intensified research efforts on the presence and effects of pesticides under real-world conditions.
39. 39
  Schwarzenbach, R. P. The challenge of micropollutants in aquatic systems Science 2006, 313, 1072– 1077 DOI: 10.1126/science.1127291
  39
  The Challenge of Micropollutants in Aquatic Systems
  Schwarzenbach, Rene P.; Escher, Beate I.; Fenner, Kathrin; Hofstetter, Thomas B.; Johnson, C. Annette; von Gunten, Urs; Wehrli, Bernhard
  Science (Washington, DC, United States) (2006), 313 (5790), 1072-1077CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
  A review. Increasing worldwide freshwater system pollution by industrial and natural chem. compds. is a key environmental problem. Although most compds. occur in low concns., many have considerable toxicol. concerns, particularly when present as components of complex mixts. This review assesses 3 scientific challenges in addressing water quality problems caused by such micro-pollutants. Tools to assess the impact of these pollutants on aquatic life and human health must be further developed and refined. Cost-effective, appropriate remediation and water treatment technologies must be explored and implemented. Use and disposal strategies coupled with the search for environmentally more benign products and processes should minimize introduction of crit. pollutants to the aquatic environment. Topics discussed include: micro-pollutant assessment in aquatic systems; mitigating aq. micro-pollutants; water quality preventive management; and outlook.
40. 40
  Verstraete, W. The manufacturing microbe Microb. Biotechnol. 2015, 8, 36– 37 DOI: 10.1111/1751-7915.12183
  40
  The manufacturing microbe
  Verstraete Willy
  Microbial biotechnology (2015), 8 (1), 36-7 ISSN:.
  There is no expanded citation for this reference.
41. 41
  Verstraete, W. The technological side of the microbiome Npj Biofilms And Microbiomes 2015, 1, 15001 DOI: 10.1038/npjbiofilms.2015.1
  There is no corresponding record for this reference.
42. 42
  van der Lelie, D.; Taghavi, S.; Henry, C.; Gilbert, J. A. The microbiome as a source of new enterprises and job creation: Considering clinical faecal and synthetic microbiome transplants and therapeutic regulation Microb. Biotechnol. 2017, 10, 4– 5 DOI: 10.1111/1751-7915.12597
  42
  The microbiome as a source of new enterprises and job creation: Considering clinical faecal and synthetic microbiome transplants and therapeutic regulation
  van der Lelie Daniel; Taghavi Safiyh; Henry Christopher; Gilbert Jack A; Henry Christopher; Henry Christopher; Gilbert Jack A; Gilbert Jack A
  Microbial biotechnology (2017), 10 (1), 4-5 ISSN:.
  There is no expanded citation for this reference.
43. 43
  http://www.quorn.com/.
  There is no corresponding record for this reference.
44. 44
  https://ec.europa.eu/food/sites/food/files/safety/docs/animal-feed-eu-reg-comm_register_feed_additives_1831-03.pdf.
  There is no corresponding record for this reference.
45. 45
  http://www.indexmundi.com/commodities/?commodity=sugar.
  There is no corresponding record for this reference.
46. 46
  http://calystanutrition.com/.
  There is no corresponding record for this reference.
47. 47
  de Visser, C. L. M.; Schreuder, R.; Stoddard, F. The EU’s dependency on soya bean import for the animal feed industry and potential for EU produced alternatives OCL: Oilseeds Fats, Crops Lipids 2014, 21, D407 DOI: 10.1051/ocl/2014021
  There is no corresponding record for this reference.
48. 48
  Kremer, T. A.; LaSarre, B.; Posto, A. L.; McKinlay, J. B. N ₂ gas is an effective fertilizer for bioethanol production by Zymomonas mobilis Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 2222– 2226 DOI: 10.1073/pnas.1420663112
  There is no corresponding record for this reference.
49. 49
  Fox, A. R. Major cereal crops benefit from biological nitrogen fixation when inoculated with the nitrogen-fixing bacterium Pseudomonas protegens Pf-5 X940 Environ. Microbiol. 2016, 18, 3522– 3534 DOI: 10.1111/1462-2920.13376
  49
  Major cereal crops benefit from biological nitrogen fixation when inoculated with the nitrogen-fixing bacterium Pseudomonas protegens Pf-5 X940
  Fox, Ana Romina; Soto, Gabriela; Valverde, Claudio; Russo, Daniela; Lagares, Antonio, Jr; Zorreguieta, Angeles; Alleva, Karina; Pascuan, Cecilia; Frare, Romina; Mercado-Blanco, Jesus; Dixon, Ray; Ayub, Nicolas Daniel
  Environmental Microbiology (2016), 18 (10), 3522-3534CODEN: ENMIFM; ISSN:1462-2912. (Wiley-Blackwell)
  Summary : A main goal of biol. nitrogen fixation research has been to expand the nitrogen-fixing ability to major cereal crops. In this work, we demonstrate the use of the efficient nitrogen-fixing rhizobacterium Pseudomonas protegens Pf-5 X940 as a chassis to engineer the transfer of nitrogen fixed by BNF to maize and wheat under non-gnotobiotic conditions. Inoculation of maize and wheat with Pf-5 X940 largely improved nitrogen content and biomass accumulation in both vegetative and reproductive tissues, and this beneficial effect was pos. assocd. with high nitrogen fixation rates in roots. 15N isotope diln. anal. showed that maize and wheat plants obtained substantial amts. of fixed nitrogen from the atm. Pf-5 X940-GFP-tagged cells were always reisolated from the maize and wheat root surface but never from the inner root tissues. Confocal laser scanning microscopy confirmed root surface colonization of Pf-5 X940-GFP in wheat plants, and microcolonies were mostly visualized at the junctions between epidermal root cells. Genetic anal. using biofilm formation-related Pseudomonas mutants confirmed the relevance of bacterial root adhesion in the increase in nitrogen content, biomass accumulation and nitrogen fixation rates in wheat roots. To our knowledge, this is the first report of robust BNF in major cereal crops.
50. 50
  Renner, J. N.; Greenlee, L. F.; Herring, A. M.; Ayres, K. E. Electrochemical synthesis of ammonia: A low pressure, low temperature approach Electrochem. Soc. Interface 2015, 24, 51– 57 DOI: 10.1149/2.F04152if
  50
  Electrochemical synthesis of ammonia: a low pressure, low temperature approach
  Renner, Julie N.; Greenlee, Lauren F.; Herring, Andrew M.; Ayers, Katherine E.
  Electrochemical Society Interface (2015), 24 (2), 51-57CODEN: ELSIE3; ISSN:1064-8208. (Electrochemical Society)
  A review. The approach of electrochem. synthesis of ammonia at low pressure and low temp.
51. 51
  Brown, K. A. Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid Science 2016, 352, 448– 450 DOI: 10.1126/science.aaf2091
  51
  Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid
  Brown, Katherine A.; Harris, Derek F.; Wilker, Molly B.; Rasmussen, Andrew; Khadka, Nimesh; Hamby, Hayden; Keable, Stephen; Dukovic, Gordana; Peters, John W.; Seefeldt, Lance C.; King, Paul W.
  Science (Washington, DC, United States) (2016), 352 (6284), 448-450CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
  Nitrogenase enzymes catalyze the biol. prodn. of fixed nitrogen. Because this is not enough to sustain modern agriculture, industrial fertilizers contg. ammonia are produced via the energy-intensive Haber-Bosch process. Brown et al. developed a way to use nitrogenase enzymes from nitrogen-fixing bacteria to make ammonia in vitro without other biol. steps or high-energy inputs. Light-activated CdS nanorods provided electrons to the FeMo nitrogenase enzyme to reduce nitrogen and produce ammonia at rates up to 64% of biol. nitrogen fixation. These nanoparticle-protein complexes show the potential for solar-driven ammonia prodn. Science, this issue p. 448.
52. 52
  Galloway, J. N.; Cowling, E. B. Reactive nitrogen and the world: 200 Years of change Ambio 2002, 31, 64– 71 DOI: 10.1579/0044-7447-31.2.64
  52
  Reactive nitrogen and the world: 200 years of change
  Galloway James N; Cowling Ellis B
  Ambio (2002), 31 (2), 64-71 ISSN:0044-7447.
  This paper examines the impact of food and energy production on the global N cycle by contrasting N flows in the late-19th century with those of the late-20th century. We have a good understanding of the amounts of reactive N created by humans, and the primary points of loss to the environment. However, we have a poor understanding of nitrogen's rate of accumulation in environmental reservoirs, which is problematic because of the cascading effects of accumulated N in the environment. The substantial regional variability in reactive nitrogen creation, its degree of distribution, and the likelihood of increased rates of reactive-N formation (especially in Asia) in the future creates a situation that calls for the development of a Total Reactive Nitrogen Approach that will optimize food and energy production and protect environmental systems.
53. 53
  Popp, A. Land-use futures in the shared socio-economic pathways Global Environmental Change 2017, 42, 331– 345 DOI: 10.1016/j.gloenvcha.2016.10.002
  There is no corresponding record for this reference.
54. 54
  Gu, B. Atmospheric Reactive Nitrogen in China: Sources, Recent Trends, and Damage Costs Environ. Sci. Technol. 2012, 46, 9420– 9427 DOI: 10.1021/es301446g
  54
  Atmospheric Reactive Nitrogen in China: Sources, Recent Trends, and Damage Costs
  Gu, Baojing; Ge, Ying; Ren, Yuan; Xu, Bin; Luo, Weidong; Jiang, Hong; Gu, Binhe; Chang, Jie
  Environmental Science & Technology (2012), 46 (17), 9420-9427CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  Human activity has intensely altered the global N cycle, producing nitrogenous gases of environmental significance, particularly in China where the most serious worldwide atm. N pollution exists. This work comprehensively assessed NH3, NOx, and N2O emissions in China based on a full cycle anal. Total reactive nitrogen (Nr) emissions more than doubled over the past 30 yr, during which the increasing trend slowed for NH3 emissions after 2000, while the increasing trend continued to accelerate for NOx and N2O emissions. Several hot-spots were identified; their Nr emissions were ∼10 times higher than others. Agricultural sources caused 95% of total NH3 emissions; fossil fuel combustion accounted for 96% of total NOx emissions; and agricultural (51%) and natural sources (forest, surface water, 39%) both contributed to Chinese N2O emissions. Total atm. Nr emission-related health damage in China (2008) reached 19-62 billion US dollars, accounting for 0.4-1.4% of its gross domestic product, of which 52-60% was from NH3 emissions and 39-47% was from NOx emissions. These results provide policy-makers an integrated view of Nr sources and health damage to address significant challenges assocd. with reduced air pollution.
55. 55
  Van Grinsven, H. J. M. Costs and benefits of nitrogen for europe and implications for mitigation Environ. Sci. Technol. 2013, 47, 3571– 3579 DOI: 10.1021/es303804g
  55
  Costs and Benefits of Nitrogen for Europe and Implications for Mitigation
  Van Grinsven, Hans J. M.; Holland, Mike; Jacobsen, Brian H.; Klimont, Zbigniew; Sutton, Mark a.; Jaap Willems, W.
  Environmental Science & Technology (2013), 47 (8), 3571-3579CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  Cost-benefit anal. can be used to provide guidance for emerging policy priorities in reducing nitrogen (N) pollution. This paper provides a crit. and comprehensive assessment of costs and benefits of the various flows of N on human health, ecosystems and climate stability to identify major options for mitigation. The social cost of impacts of N in the EU27 in 2008 was estd. between euro75-485 billion per yr. A cost share of around 60% is related to emissions to air. The share of total impacts on human health is ∼45% and may reflect the higher willingness to pay for human health than for ecosystems or climate stability. Air pollution by nitrogen also generates social benefits for climate by present cooling effects of N contg. aerosol and C-sequestration driven by N deposition, amounting to an estd. net benefit of about euro5 billion/yr. The economic benefit of N in primary agricultural prodn. ranges between euro20-80 billion/yr and is lower than the annual cost of pollution by agricultural N which is in the range of euro35-230 billion/yr. Internalizing these environmental costs would lower the optimum annual N-fertilization rate in Northwestern Europe by ∼50 kg/ha. Acknowledging the large uncertainties and conceptual issues of our cost-benefit ests., the results support the priority for further redn. of NH3 and NOx emissions from transport and agriculture beyond commitments recently agreed in revision of the Gothenburg Protocol.
56. 56
  Sobota, D. J.; Compton, J. E.; McCrackin, M. L.; Singh, S. Cost of reactive nitrogen release from human activities to the environment in the United States Environ. Res. Lett. 2015, 10, 025006 DOI: 10.1088/1748-9326/10/2/025006
  56
  Cost of reactive nitrogen release from human activities to the environment in the United States
  Sobota, Daniel J.; Compton, Jana E.; McCrackin, Michelle L.; Singh, Shweta
  Environmental Research Letters (2015), 10 (2), 025006/1-025006/13CODEN: ERLNAL; ISSN:1748-9326. (IOP Publishing Ltd.)
  Leakage of reactive nitrogen (N) from human activities to the environment can cause human health and ecol. problems. Often these harmful effects are not reflected in the costs of food, fuel, and fiber that derive from N use. Spatial analyses of damage costs attributable to source at management relevant scales could inform decisions in areas where anthropogenic N leakage causes harm. We used recently compiled data describing N inputs in the conterminous United States (US) to assess potential damage costs assocd. with anthropogenic N. We estd. fates of N leaked to the environment (air/deposition, surface freshwater, groundwater, and coastal zones) in the early 2000s by multiplying watershed-level N inputs (8-digit US Geol. Survey Hydrol. Unit Codes; HUC8s) with published coeffs. describing nutrient uptake efficiency, leaching losses, and gaseous emissions. We scaled these N leakage ests. with mitigation, remediation, direct damage, and substitution costs assocd. with human health, agriculture, ecosystems, and climate (per kg of N) to calc. annual damage cost (US dollars in 2008 or as reported) of anthropogenic N per HUC8. Ests. of N leakage byHUC8 ranged from <1 to 125 kg N ha-1 yr-1, with most N leaked to freshwater ecosystems. Ests. of potential damages (based on median ests.) ranged from $1.94 to $2255 ha-1 yr-1 across watersheds, with a median of $252 ha-1 yr-1. Eutrophication of freshwater ecosystems and respiratory effects of atm. N pollution were important across HUC8s. However, significant data gaps remain in our ability to fully assess N damages, such as damage costs from harmful algal blooms and drinking water contamination. Nationally, potential health and environmental damages of anthropogenic N in the early 2000s totaled $210 billion yr-1 USD (range: $81-$441 billion yr-1). While a no. of gaps and uncertainties remain in these ests., overall this work represents a starting point to inform decisions and engage stakeholders on the costs of N pollution.
57. 57
  Muller, N. Z.; Mendelsohn, R. O. Weighing the Value of a Ton of Pollution Regulation 2010, 33, 20
  There is no corresponding record for this reference.
58. 58
  Kusiima, J. M.; Powers, S. E. Monetary value of the environmental and health externalities associated with production of ethanol from biomass feedstocks Energy Policy 2010, 38, 2785– 2796 DOI: 10.1016/j.enpol.2010.01.010
  There is no corresponding record for this reference.
59. 59
  Erisman, J. W. Consequences of human modification of the global nitrogen cycle Philos. Trans. R. Soc., B 2013, 368, 20130116 DOI: 10.1098/rstb.2013.0116
  59
  Consequences of human modification of the global nitrogen cycle
  Erisman, Jan Willem; Galloway, James N.; Seitzinger, Sybil; Bleeker, Albert; Dise, Nancy B.; Petrescu, A. M. Roxana; Leach, Allison M.; de Vries, Wim
  Philosophical Transactions of the Royal Society, B: Biological Sciences (2013), 368 (1621), 20130116/1-20130116/9CODEN: PTRBAE; ISSN:0962-8436. (Royal Society)
  The demand for more food is increasing fertilizer and land use, and the demand for more energy is increasing fossil fuel combustion, leading to enhanced losses of reactive nitrogen (Nr) to the environment. Many thresholds for human and ecosystem health have been exceeded owing to Nr pollution, including those for drinking water (nitrates), air quality (smog, particulate matter, ground-level ozone), freshwater eutrophication, biodiversity loss, stratospheric ozone depletion, climate change and coastal ecosystems (dead zones). Each of these environmental effects can be magnified by the 'nitrogen cascade': a single atom of Nr can trigger a cascade of neg. environmental impacts in sequence. Here, we provide an overview of the impact of Nr on the environment and human health, including an assessment of the magnitude of different environmental problems, and the relative importance of Nr as a contributor to each problem. In some cases, Nr loss to the environment is the key driver of effects (e.g. terrestrial and coastal eutrophication, nitrous oxide emissions), whereas in some other situations nitrogen represents a key contributor exacerbating a wider problem (e.g. freshwater pollution, biodiversity loss). In this way, the central role of nitrogen can remain hidden, even though it actually underpins many trans-boundary pollution problems.
60. 60
  Compton, J. E. Ecosystem services altered by human changes in the nitrogen cycle: A new perspective for US decision making Ecology Letters 2011, 14, 804– 815 DOI: 10.1111/j.1461-0248.2011.01631.x
  60
  Ecosystem services altered by human changes in the nitrogen cycle: a new perspective for US decision making
  Compton Jana E; Harrison John A; Dennis Robin L; Greaver Tara L; Hill Brian H; Jordan Stephen J; Walker Henry; Campbell Holly V
  Ecology letters (2011), 14 (8), 804-15 ISSN:.
  Human alteration of the nitrogen (N) cycle has produced benefits for health and well-being, but excess N has altered many ecosystems and degraded air and water quality. US regulations mandate protection of the environment in terms that directly connect to ecosystem services. Here, we review the science quantifying effects of N on key ecosystem services, and compare the costs of N-related impacts or mitigation using the metric of cost per unit of N. Damage costs to the provision of clean air, reflected by impaired human respiratory health, are well characterized and fairly high (e.g. costs of ozone and particulate damages of $28 per kg NO(x)-N). Damage to services associated with productivity, biodiversity, recreation and clean water are less certain and although generally lower, these costs are quite variable (<$2.2-56 per kg N). In the current Chesapeake Bay restoration effort, for example, the collection of available damage costs clearly exceeds the projected abatement costs to reduce N loads to the Bay ($8-15 per kg N). Explicit consideration and accounting of effects on multiple ecosystem services provides decision-makers an integrated view of N sources, damages and abatement costs to address the significant challenges associated with reducing N pollution.
61. 61
  Birch, M. B. L.; Gramig, B. M.; Moomaw, W. R.; Doering, O. C., III; Reeling, C. J. Why Metrics Matter: Evaluating Policy Choices for Reactive Nitrogen in the Chesapeake Bay Watershed Environ. Sci. Technol. 2011, 45, 168– 174 DOI: 10.1021/es101472z
  61
  Why Metrics Matter: Evaluating Policy Choices for Reactive Nitrogen in the Chesapeake Bay Watershed
  Birch, Melissa B. L.; Gramig, Benjamin M.; Moomaw, William R.; Doering, Otto C., III; Reeling, Carson J.
  Environmental Science & Technology (2011), 45 (1), 168-174CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
  Despite major efforts, the redn. of reactive N (rN) using traditional metrics and policy tools for the Chesapeake Bay has slowed in recent years. We apply the concept of the N Cascade to the chem. dynamic nature and multiple sources of rN to examine the temporal and spatial movement of different forms of rN through multiple ecosystems and media. We also demonstrate the benefit of using more than the traditional mass fluxes to set criteria for action. The use of multiple metrics provides addnl. information about where the most effective intervention point might be. Utilizing damage costs or mortality metrics demonstrates that even though the mass fluxes to the atm. are lower than direct releases to terrestrial and aquatic ecosystems, total damage costs to all ecosystems and health are higher because of the cascade of rN and the assocd. damages, and because they exact a higher human health cost. Abatement costs for reducing rN releases into the air are also lower. These findings have major implications for the use of multiple metrics and the addnl. benefits of expanding the scope of concern beyond the bay itself and support improved coordination between the Clean Air and Clean Water Acts while restoring the Chesapeake Bay.
62. 62
  Brink, C.; van Grinsven, H. J. M. In The European Nitrogen Assessment; Sutton, M. A., Ed.; Cambridge University Press: Cambridge, 2011.
  There is no corresponding record for this reference.

Microbes and the Next Nitrogen RevolutionClick to copy article linkArticle link copied!

Environmental Science & Technology

Abstract

The Haber Bosch Process: An Invention that Changed the World

Figure 1

The Nitrogen Cycle to Come

Figure 2

Microbial Protein Production Is a Very Efficient Way to Produce Valuable Protein

Bacteria Can Use a Broad Range of Carbon Sources

Figure 3

Bacterial Protein Production Has Many Additional Environmental Benefits

Land Use Change, Greenhouse Gas Emissions, and Biodiversity Loss

Phosphorus Pollution

Fresh Water Withdrawals

Pesticides

Opportunities and Challenges

Technological Implementation

Establishing a Large-Scale Demand for MP

Cost Competitiveness of MP

Toward Protein Self-Sufficiency

Concluding Remarks

Author Information

Biographies

Ilje Pikaar

Silvio Matassa

Korneel Rabaey

Benjamin Leon Bodirsky

Alexander Popp

Mario Herrero

Willy Verstraete

References

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Abstract

Figure 1

Figure 2

Figure 3

References

Microbes and the Next Nitrogen Revolution
Click to copy article linkArticle link copied!