One Man’s Compost Is Another Man’s Fuel

Just as we’ve finally been rewired to think that the most eco-friendly place for those overripe fruits and vegetables is in the compost bin, there may soon be an even better option. Rather than turn fruits and veggies back into fuel for your garden, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart, Germany, want to turn them into biogas fuel for your car.

Seeing natural gas as a better alternative to gasoline or diesel, with less C02 released in its emissions and almost no soot particles, these researchers aim to overcome the major downsides—that it is still a fossil fuel with all the issues that go along with that, and the supply is far from endless. So they’re turning to the compost bin, where the process is actually pretty simple. When food waste ferments it produces methane, which the researchers then compress into high-pressure cylinders to be used as fuel.

Stuttgart Biogas Plant

image via Fraunhofer IGB

In early 2012, the researchers will test out a pilot plant next to Stuttgart’s wholesale market to get first dibs on all the picked-over fruits and vegetables. Once the food is in hand, they will use various microorganisms to generate methane in a two-stage digestion process. Because the waste is high in water content and low in lignocelluloses content, rapid fermentation is possible, only taking a few days.

While seemingly straightforward, it may be awhile before we’re all sporting bumper stickers stating, “Powered by Fruits and Veggies.” Relying on the whims of market customers and Mother Nature’s influence over what goes bad first, the mix of fruits and vegetables varies day by day. If a lot of oranges went bad, the high acid content requires the researchers to adjust the pH levels.

Angeli Duffin is a Midwest transplant currently living in San Francisco, CA. Kicking off her career doing product design and development with Fair Trade artisans around the world, she then moved on to the editorial side, writing for eBay’s Green Team blog and working as a marketing consultant for social and environmentally minded companies