- eawag.ch
First, let’s get something clear. Fecal sludge* is different from sewage. Sewage, at least the American version, consists of wastewater as well as what gets flushed down the toilet. Fecal sludge is human biowaste alone. Unless you’re dealing with a bed pan situation, you don’t know fecal sludge. The closest most Americans come to fecal sludge is when using a porta-potty. And even then it’s mixed with sanitizing chemicals.
In countries without developed sewer systems, disposing fecal sludge is an everyday fact of life. It has to get dumped somewhere, and oftentimes that somewhere is the local river. The same river people bathe in and drink from.
A few years ago Columbia University environmental engineer Kartik Chandran visited Ghana, where he watched villagers discard fecal sludge into a local stream. He thought there had to be a better option for waste management.
“That’s what I do,” Chandran told me over the phone yesterday afternoon, “I look for strategies for improving human health.” He knew he had to find a way to treat the fecal sludge, but he needed to do it in a way that was financially sustainable for a developing nation.
Human waste contains organic compounds like fatty acids and fats. Some of those organic acids, when combined with methanol, form a methyl ester of those fatty acids. These methyl esters are what make up biodiesel, a biofuel. Other organic compounds in fecal sludge can be converted to methane, another biofuel. Chandran realized that a waste processing facility would also operate as a biorefinery.
Engineers have converted sewage sludge to biodiesel before, but Chandran is the first to attempt the process with fecal sludge. The Bill and Melinda Gates Foundation recently awarded his US-Ghanaian team $1.5 million to build a biorefinery in Ghana.
Considering all the infrastructure such a biorefinery will require, I had to wonder whether it could really be profitable. That depends on your idea of net gains, says Chandran. They’ll be treating fecal sludge that would ordinarily go into surrounding water bodies. That will have an immediate benefit on human health, and healthcare costs. The project will go on for the next two years, enough time Chandran says, to get an idea of what their ultimate fuel yield will be.
I’m a sucker for anything that sounds like the realization of sci-fi novel technology, and turning biowaste into fuel seems just that amazing. Whether it will be successful enough to gain widespread implementation is yet to be seen, but I’ll be interested to observe the progress.
*This gem of a term is novel to me, so please excuse the over-use. I am quite taken by the repulsive strength of these two words. “Sludge” alone sounds like a dirtier, muckier version of mud, disgusting in its own right. And “fecal” not only denotes images of poop, but gains further distaste in its similarity to the word “fetus”.