Fecal Fuel

Science, technology, and life.
April 13 2009 9:24 AM

Fecal Fuel

Several days ago, we looked at "toilet to tap," the increasingly useful art of turning sewage into drinking water . Orange County, Calif., which is pioneering the practice, is proud to tell you how thoroughly its filtration purges the sewage : "Thousands of microfilters, hollow fibers covered in holes one-three-hundredth the width of a human hair, strain out suspended solids, bacteria and other materials."

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William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.

But what if the water isn't what you want? What if you want the sewage?

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Who would want these lovely "suspended solids," you ask? Why, you would. Apparently, they're a fine source of environmentally friendly fuel. Agence France Presse  reports that in Oslo, Norway,

city officials soon plan to introduce buses that run on biofuels extracted from human waste. ... The biofuel, which is methane generated by fermenting sludge, will come from the Bekkelaget sewage treatment plant which handles waste from 250,000 city dwellers. "By going to the bathroom, a person produces the equivalent of eight litres (2.1 gallons) of diesel per year. That may not seem like a lot, but multiplied by 250,000 people, that is enough to operate 80 buses for 100,000 kilometres (62,000 miles) each," [one official] says.

Fecal fuel is, if you'll pardon the expression, green:

In addition to being carbon neutral, it emits 78 percent less nitrogen oxide and 98 percent fewer fine particles—two causes of respiratory illnesses—and is 92 percent less noisy. ... "If our entire fleet switched to biomethane, carbon dioxide emissions would be reduced by around 30,000 tonnes per year," according to [an Oslo official].

It protects the food supply:

Contrary to first generation bio-ethanol, made from grains and plants, biomethane has the added advantage of not impacting food supplies, nor does it require fertilisation or deplete precious water resources.

In other words, instead of turning corn into fuel, which prevents you from eating the corn , we should feed you the corn first and then collect your droppings so that your sustenance becomes part of the fuel production process.

And it's cheap:

All included, the cost of producing biofuel equivalent to one litre of diesel comes to 0.72 euros (98 cents), while diesel at the pump in Norway currently costs more than 1.0 euro.

In fact, as a fuel supplier, maybe you should get a cut of the savings. Remember that pilot project in India I mentioned last year? The one where villagers get paid to use public toilets while their urine is tested for use as a fertilizer? At the time, I proposed that

we could try our own version of the Indian experiment. To do that, we'd need to devise an efficient method of converting public-toilet waste into something productive, such as fertilizer, without endangering public health. ... I bet somebody will figure out pretty soon how to monetize toilet waste. ... Restaurant grease [is] being illegally siphoned from filthy bins and barrels. Bandits are selling it for conversion to biodiesel. When bandits start siphoning public toilets, maybe governments will wake up and get in on the action. And you'll stop having to pay.

Nine months later, Oslo may have worked out the last piece of the puzzle. You go to the bathroom. We filter the excrement from the water. We recycle the water so you can drink it again. Meanwhile, we turn the excrement into fuel. All of this helps the environment, protects the food supply and saves money. And if you play it right, you get paid.

Anyone got a problem with this?