[This is an EXCERPT: read the whole article here. The full article goes more into depth on the limitations of the current stock of biogas cars. Also notable is that biogas is a technology that uses waste to make energy, and can use existing natural gas infrastructure. -Ed.]

by James Kanter

Goteborg, Sweden is "among dozens of municipalities in Sweden with facilities that transform sewage waste into enough biogas to run thousands of cars and buses."

"Cars using biogas created a stir when they began to be rolled out on a large scale at the start of the decade. The tailpipe emissions are virtually odorless, the fuel is cheaper than gasoline and diesel, and the idea of recovering energy from toilet waste appealed to green-minded Swedes."

"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."

Photo credit: Brian Mitchell