I think we can all agree that there is no doubt that sewage sludge is the very definition of a waste product. According to a new EPA report, biodiesel generated from the sewage sludge leftover after wastewater treatment costs just 10 cents more per gallon than conventional diesel.
The secret ingredient is the addition of oil-producing bacteria that create the biofuels as a waste product during photosynthesis. Research at Arizona State University showed that genetic engineering of these photosynthetic bacteria can help to maximize the biodiesel output they release. Potentially, this type of sewage-generated biodiesel could be on the market for as little as $3.11 per gallon (less than regular gas in Seattle, thank you very much!)
There are a few potential stumbling blocks here, though. According to Inhabitat,
The best practices for getting biodiesel this way have hardly been worked out yet, according to the study by EPA scientist David Kargbo. Among the biggest problems is finding a way to collect sludge that is high in lipids — the material the reaction uses — ensuring that traces of pharmaceutical chemicals don’t make it into the fuel. Finally, regulators haven’t even begun to assess what it would mean to transfer large amounts of sewage sludge to private companies for processing into biodiesel.Operationally, it seems like retrofitting all of our sewage-treatment plants to create large amounts of commercially-viable biodiesel could be very challenging. But compared to other biodiesel alternatives like waste vegetable oil from restaurants or soy-based biodiesel from the Amazon rainforest, the idea is looking more attractive every day.