Environmental Technology
Runner-up: Microbial fuel cells 101
“Microbial Fuel Cells: Methodology and Technology” by Bruce Logan, Pennsylvania State University; Bert Hamelers, Wageningen University, The Netherlands; René Rozendal, Wageningen University and Wetsus, Centre for Sustainable Water Technology, The Netherlands; Uwe Schröder, University of Greifswald, Germany; Jürg Keller and Stefano Freguia, The University of Queensland, Australia; Peter Aelterman, Willy Verstraete, and Korneel Rabaey, Ghent University, Belgium, 2006, 40 (17), 5181–5192.
The day after Korneel Rabaey’s thesis defense—and on the heels of a celebratory evening with a “bit” of Belgian beer and some French wine—a group of microbial fuel cell (MFC) researchers gathered for a brief meeting in Ghent, Belgium. The result was their ES&T paper, a review article intended as a guideline for the growing number of researchers interested in MFCs. The launch of the paper also coincided with the creation of a heavily accessed MFC website, notes Rabaey.
People were asking worldwide: how do I build one, how do they work, what do I need to get started? Therefore, the group envisioned a nuts-and-bolts paper that would tell people about all the essential aspects of an MFC and, particularly, how to make one, says corresponding author Bruce Logan. He notes that coordinating a paper written by nine authors was tricky. The manuscript followed the sun around the globe, from Pennsylvania to Australia, to Europe, and back to Pennsylvania via email.
At a basic level, an MFC works by converting biochemical energy into electrical energy. When bacteria digest sugar, protein, or other biodegradable organic matter, including bits of matter in wastewater, they produce electrons. In an MFC, electrons flow through a wire from an anode to a cathode, generating electricity. Given a little energy boost, MFCs can also yield hydrogen gas.
MFCs have yet to find their way out of the lab, and they generate only small amounts of power. However, as technical barriers give way, wattage goes up. To evolve from a scientific curiosity into a practical technology, MFCs must be characterized in terms engineers can evaluate and appreciate, according to coauthor Willy Verstraete. This was a primary goal of the paper.
A major question addressed at the meeting was: what are the best units to express the power generated by an MFC? “I wouldn’t say we reached consensus on everything,” says Logan. “But we at least appreciated that you had to do it more than one way,” he adds. The group decided that it was reasonable to continue reporting power per area—of the anode, most often—because that is how people had been doing it, but that reporting power per volume was equally, if not more, important.
Although this nascent technology is not yet ready for prime time, Logan speculates that eventually MFCs will find multiple uses. The current goal is to scale up. Logan suspects that the first practical application will be using leftover organic matter in wastewater to help power sewage treatment. Both Verstraete and Logan stress the importance of attracting the interest of industry and investors, and Logan says that several companies are paying attention.
