Filling a vital need: the unknown story of waste to energy
BA few weeks ago I lost the use of my toilet and learned firsthand just how much I missed it when it wasn’t there.
My plumbing went out of order when the pipe between my house and the city’s sewer line in the street collapsed. Pipes like that belong to the homeowner, so it was my responsibility to get it fixed. It took about a week for the workmen to come and replace it. During that week I had to go to the local fast food place to use the facilities. It got old fast.
More than 2 billion people around the world today don’t have a toilet or even an outhouse. They must relieve themselves beside the road or behind a bush. I’ve been reading about sanitation – and the lack of it – in a book called “The Big Necessity” by Rose George.
Toilets and the modern treatment of human waste make a difference not just to our comfort, but also to basic human health. Our bodily waste can carry bacteria, viruses, and parasites. If the waste comes into contact with water that’s later used for drinking, people can become violently ill.
The Chinese work very hard to address their waste problem. With over a billion people, they have a monumental task in disposing of all that waste on a daily basis. In the countryside one approach they sometimes use is a device called an anaerobic digester. It’s a vessel in which natural processes that break down waste without much oxygen present can proceed. Human waste is one material added to the digesters, but things like pig excrement can also be inputs. As they break down they form gas and solids that are less hazardous to human health.
One of the products of digesters is methane, called “biogas” in this context. It’s the same chemical that’s the main ingredient in the “natural gas” we burn in our furnaces. Biogas in some parts of rural China is used as fuel for cook stoves. Compared to burning wood to cook, it’s convenient and of course it conserves trees.
Digesters can break down things other than sewage. The same basic biological processes can help break down agricultural waste. But the sewage-to-fuel process surprises people the most, an example of making something valuable out of hazardous materials.
On more than one occasion I’ve taken students to tour my local sewage treatment plant. (I think they should know what happens to their waste as part of being generally informed citizens and residents of the planet.) The anaerobic digesters at the plant produce methane. At least sometimes, that methane has been burned to provide heat to breakdown more waste. And sometimes it’s burned off in a flame atop the digester.
Most Americans don’t know much about where their waste goes or how it’s treated and released into the general environment. Here’s hoping we can get over our embarrassment about our bodily waste and educate ourselves at least about the basics of wastewater treatment.
Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Her most recent book is “The Whole Story of Climate,” just published by Prometheus Books. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.