More inspiring green technology news from Scandinavia. Apparently there is a Swedish company that makes gas from human waste. Yup - what you flush down the toilet every morning. Here comes the science:
Chemically, biogas is the same as natural gas from fossil fuels, but its manufacture relies on a process where bacteria feed on fecal waste for about three weeks in an oxygen-free chamber. The result is two-thirds methane and one-third carbon dioxide, as well as a nutrient-rich residue that can be used as soil or construction material.
Once the methane is purified, it is pumped through Goteborg’s network of gas pipelines to specialized filling stations, where it is pressurized for delivery. Any car with an engine and tank configured for compressed natural gas can use biogas.
Apparently, it’s cheaper than gasoline and diesel, and though slightly more expensive than ethanol per unit, it’s more efficient, compensating for the price gap.
So what’re the downsides? Plenty, actually. First, the fuel isn’t all that efficient. Car fuel tanks are huge (crowding out trunk space), but only hold enough for about 2-3 hours of driving. Some owners have apparently also complained that the cars don’t do well on steep climbs and can be sluggish in certain kinds of weather. Perhaps as a result, Volvo stopped making biofuel cars in 2006, dealing a blow to the prospects for market expansion. Also, from an American perspective, part of the supposed “low cost” of biofuels is almost certainly artificial - fueled by high Swedish taxes on gas, government subsidies for biofuel station construction, and tax breaks for people who buy biofuel cars. Furthermore, it doesn’t seem to be that great of a supply:
Ola Fredriksson, an engineer at Gryaab, the sewage facility in Goteborg, said that what an average person flushed down the toilet each year created enough biogas to drive 120 kilometers, or 75 miles.
The average American (as well as the average Swede, for that matter) travels quite a bit further than that in a year. Even with the recent drop in highway miles travelled, Americans still clocked 688.7billion highway miles in March alone. If every American gets 75 highway miles a year, that comes to a total of 22.5billion miles - or just over 3% of what we actually travelled in just one month. Which is like saying that people would have to poop at least 396 times more than they do to cover yearly highway travel in the US.
No one has that kind of time or dedication.
Still, the idea of dumping human waste into the city’s natural gas grid (which is how it actually works in some places in Sweden: the drivers put natural gas in their car, and in return the city natural gas grid accepts an offset amount of biofuel) is appealing. It doesn’t solve any large-scale energy problems, but it does at least find something useful to do with the sewer system.
The prospects? This 2007 Swedish government report claims that there are 11,000 biofuel cars in Sweden being served by at least 71 fueling stations. That’s a start.