Bioengineers at Oregon State University (OSU) have developed a microbial fuel cell that can treat waste water — and generate significant amounts of electricity at the same time.

The microbial fuel cell (MFC) works much like a normal fuel cell, but it uses waste water as a fuel (instead of hydrogen or ethanol), and specially-crafted bacteria act as a catalyst (instead of platinum). In the case of this fuel cell, developed by Hong Liu and her OSU colleagues, waste water comes into the fuel cell (at the anode), and bacteria oxidizes the organic compounds, producing spare electrons that flow to the cathode — creating electricity. The anode and cathode are separated by a membrane that only clean water can pass through, purifying the waste water.

All told, the MFC produces two kilowatts of power per cubic meter of bioreactor volume — not a huge amount, but apparently 10 to 50 times more power electricity than other MFCs on the market.

Compare this MFC with conventional waste water processing plants, which for almost 100 years have used activated sludge to clean the water. Activated sludge was developed way back in 1913, and it also uses bacteria to break down organic compounds in waste water — but unlike the MFC, the process consumes a lot of electricity, rather than producing it. According to the OSU, around 3% of the United States’ power consumption is spent on treating waste water.

Suffice it to say, if the treatment of waste water actually produced electricity, we’d be onto a very good thing indeed. Not only does the MFC provide a very green source of electricity, it would also be hugely helpful to developing countries that don’t have reliable access to electricity or lack water treatment plants. Even if MFCs can only produce 1% of the US’s power requirements, that would still be a total swing of 4% — a truly vast amount of money/oil.

Research paper: DOI: 10.1039/C2EE21964F