Sparks

Dirty water = clean energy

 By Robin Wylie

Humans have been harnessing the power of water for thousands of years, but never like this. A new study has managed to generate significant amounts of electricity from industrial wastewater using only the power of its naturally-occurring bacteria. “Microbial Fuel Cells” – in which electricity is produced using an electrochemical gradient produced by bacteria – have been around for years. But now it seems that using microbes to produce clean energy could be even easier, and cheaper, than we once thought…

(Cover photo E. Coli bacteria by NIAID)

Water works well for us. Living on a planet that’s literally bathed in the stuff, it’s no surprise that we’ve found ways to squeeze as much energy from this molecule as we can.

But perhaps we should be squeezing harder. A new study has found that even the water we throw away could have hidden (electrical) potential.

Scientists from South Korea, Egypt and Saudi Arabia have just shown that industrial wastewater can be used to generate electricity using only the bacteria naturally present in the water as a power source. As a bonus, the process even treats the wastewater at the same time.

The researchers used wastewater, which they obtained from food, dairy and alcohol factories in South Korea, to make various “microbial fuel cells” — systems which use electrodes coated with bacteria to generate electrical power, via catalytic reactions carried out naturally by the microbes themselves.

In the study, the scientists managed to generate one watt of electrical power per cubic meter of wastewater (this was for food wastewater, the alcohol and dairy wastewaters were about half as effective).

 

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The only power input a microbial fuel cell requires is a chemical food source for the bacteria, which in the case of the new study came entirely from the organic compounds already present within the wastewater (byproducts of the food, alcohol and dairy processing).

Microbial fuel cells had been used to generate electricity from wastewater before, but this is the first time this feat has been achieved using raw wastewater; previous studies had added chemicals to the wastewater to enhance its electrical productivity.

A useful side-effect of microbial fuel cells is that they actually treat the wastewater at the same time as producing power. This means that as well as being a potential source of clean energy, wastewater-powered microbial fuel cells could also be a source of clean water.

Humans dump millions of tons of industrial wastewater each year. But science is showing that this liquid could be much more useful than its name suggests.

about the author
Robin Wylie
Freelance earth/space science journalist. Currently finishing off a PhD in volcanology at University College London.