Traded Plastic, Traded Impacts? Designing Counterfactual Scenarios to Assess Environmental Impacts of Global Plastic Waste Trade

The global trade of plastic waste has raised environmental concerns, especially regarding pollution in waste-importing countries. However, the overall environmental contribution remains unclear due to uncertain treatment shares between handling plastic waste abroad and domestically. Here, we conduct a life cycle assessment of global plastic waste trade in 2022 across 18 countries and six plastic waste types, alongside three “nontrade” counterfactual scenarios. By considering the required cycling rate, which balances importers’ costs and recycling revenues, we find that the trade resulted in lower environmental impacts than treating domestically with the average treatment mix. The trade scenario alone reduced climate change impact by 2.85 million tonnes of CO2 equivalent and mitigated damages to ecosystem quality, human health, and resource availability by 12 species-years, 6200 disability-adjusted life years (DALYs), and 1.4 billion United States dollars (USD in 2013), respectively. These results underscore the significance of recognizing plastic waste trade as a pivotal factor in regulating global secondary plastic production when formulating a global plastics treaty.


Supplementary table
Table S1.The selected research on quantifying the environmental impacts of plastic waste trade.

Research
Main results

Highlights limitations
Wen, Xie, • Detailed trade flow data at the state level.
• Uniform treatment setting for importing countries outside the USA.

Adams and
Zhao 4 Global plastic waste trade had a net emission reduction of 8.27 Mt CO 2 -eq in 2012.
• Linking environmental input-output analysis.
• Without reference to a no-trade scenario.

Geyer and
Suh 5 China's plastic waste import ban may exacerbate environmental impacts both in China and globally.
• Specified plastic waste (PET) in LCA • Considered recycling and landfill only.
• Uniform treatment setting for importing countries outside China.

Sun and
Tabata 6 A post-ban carbon emission surge in both China and Japan.
Fig. S6.Sensitivity analysis for the remaining impact categories under four scenarios (the second part).The variance exceeds or equals 100% as the bar reaches its endpoint.The length and colour depth of the horizontal bars are proportional to the range of sensitivity results derived from pessimistic and optimistic cases.The characterization factors with full names are ionising radiation potential (irp; kg Co-60-eq), agricultural land occupation (lop; m2*a cropeq), surplus ore potential (sop; kg Cu-eq), ozone depletion potential (odpinfinite: kg CFC-11eq), particulate matter formation potential (pmfp; kg PM2.5-eq), photochemical oxidant formation potential: human health (hofp; kg NOx-eq), photochemical oxidant formation potential: terrestrial ecosystems (eofp; kg NOx-eq), water consumption (wcp; cubic meter).

Fig. S2 .
Fig. S2.The system boundary of mechanical recycling of waste PVC in LCA.The figure is adapted from Ye, Qi, Hong and Ma 45 .We excluded the collection and sorting processes.

Fig. S3 .
Fig. S3.The system boundary of mechanical recycling of waste PET in LCA.The figure is adapted from Shen, Worrell and Patel 84 .

Fig. S4 .
Fig. S4.The environmental impacts of plastic waste trade under four scenarios in 2022 across the remaining impact categories from the ReCiPe midpoint (H).

Table S2 .
The domestic average plastic treatment mix among 18 research countries (unit: %).

Table S3 .
The share of plastic types in recycling across countries.Research countries without data instead use regional averages.

Table S4 .
The required recycling rates across 18 research countries and four plastic waste types.

Table S5 .
Original unit processes and adjustments in LCI databases of Ecoinvent 3.8 and LCA Commons.'Row' is short for 'Rest of the world'.

Table S6 .
35fe cycle inventories for mechanical recycling of high density polyethene (HDPE) with lower and upper ranges.The original life cycle inventory is derived from Civancik-Uslu, Nhu, Van Gorp, Kresovic, Larrain, Billen, Ragaert, De Meester, Dewulf and Huysveld35.For other adjustments see references.
*As the same value as in the low impact.

Table S7 .
35fe cycle inventories for mechanical recycling of low density polyethene (LDPE) with lower and upper ranges.The original life cycle inventory is derived from Civancik-Uslu, Nhu, Van Gorp, Kresovic, Larrain, Billen, Ragaert, De Meester, Dewulf and Huysveld35.For other adjustments see references.
* As the same value as in the low impact.

Table S8 .
35fe cycle inventories for mechanical recycling of polystyrene (PS) with lower and upper ranges.The original life cycle inventory is derived from Civancik-Uslu, Nhu, Van Gorp, Kresovic, Larrain, Billen, Ragaert, De Meester, Dewulf and Huysveld35.For other adjustments see references.
* As the same value as in the low impact.

Table S9 .
45fe cycle inventories for mechanical recycling of polyvinyl chloride (PVC) with lower and upper ranges.The original life cycle inventory is derived from Ye, Qi, Hong and Ma45.For other adjustments see references.

Table S10 .
40fe cycle inventories for mechanical recycling of polyethene terephthalate (PET) with lower and upper ranges.The original life cycle inventory is derived from Ecoinvent 3.840.For other adjustments see references.
* As the same value as in the low impact.

Table S11 .
40fe cycle inventories for mechanical recycling of polypropylene (PP) with lower and upper ranges.The original life cycle inventory is derived from Ecoinvent 3.840.For other adjustments see references.
* As the same value as in the low impact.

Table S12 .
Life cycle inventory of Incineration (with energy recovery) among six plastic waste types and 18 research countries with lower and upper ranges.  ,,, * -  ,,, * *   ,,, indicates the avoided net energy generation by incinerating 1 kg of plastic  in country  calculated by using the maximu m value of net energy generation and the maximu m value of the lower heating value of plastic in Eq.4.Ditto for   ,,, .

Table S13 .
Recovered electricity and heat from municipal waste incineration.Bottom ash for road construction and metal recycling are not considered.SYSAV is short for Sysav South Scania waste-to-energy plant.

Table S14 .
Comparison of lower heating values (LHV) reported in the literature for principal components of plastics in the waste stream (unit: MJ/kg).The table originated from Themelis, Castaldi, Bhatti and Arsova 77 .

Table S15 .
Substitution factors of secondary plastic to primary plastic regarding technical properties.The maximum and minimum values for each plastic are dropped when calculating the average value and selecting the range.The average range value of the substitution factor is assigned to plastic PS and PVC as no sufficient data is provided.: A measure of the duration of a dissolved polymer to dilute through a specified capillary.II : Flexural modulus denotes the ability of a plastic material to bend.III : The material's resistance to elastic deformation.VI : The material's ability to withstand an applied load without failure (tensile strength) or plastic deformation (yield stress). I