Tuesday, July 3, 2012

In the grip of energy

Wastewater treatment involves steps like separation, settling, filtration, biological digestion, and chemical treatment. This means a lot of equipment and energy consumption! One evaluation has estimated that wastewater treatment uses 2% of the United States’ overall energy consumption.
Scientists now have come up with a microbial fuel cell (MFC) that has a 13% energy recovery capacity which means wastewater treatment for free making it possible for poor nations to find clean water affordably from wastewater.
While traditional fuel cells convert fuel into electricity without igniting it (combining hydrogen and oxygen, as in the hydrogen fuel cell), an MFC uses organic matter as the fuel and microbes to break them down.  As the microbes break down the organic matter, electrons (the movement of which constitutes electricity) are produced.  The new MFC uses sewage from a bog standard sewage treatment plant. It’s made of a sealed container and an unsealed container, separated by a membrane.
The microbes grow in a film on an electrode in the sealed chamber, sending electrons to the electrode and protons to the unsealed container. Oxygen in that container plus microbes on a second electrode plus the electrons from the sealed chamber combine to produce things that are not sewage and generate some electricity in the process.
The device also removes the vast majority of organic matter and potentially disease-causing microbes, though not quite at the point of creating drinkable water along with electricity. But it is a step towards that. Today, every activity involves some energy expenditure. That is how comfort has been introduced into our lives – by using energy. That was fine at a time when energy was believed to be abundant. Today the move should be to release more and more of these processes from dependence on energy, at least energy from fossil fuels.

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