02-06-09 by dugan
You know the coffee can full of bacon grease that Grandma used to keep for frying? Or, in parts of the South, to drizzle on bread? Well, yeah, it was tasty but not so good for you, and most people now either put it down the drain (bad) or stick the full coffee can in the garbage (better). San Francisco, however, is about to make this "brown grease"into biodiesel for city buses and fuel oil for powering sewage plants. The point isn’t just making fuel–it won’t be a great price per gallon–but making use of some very bad sludge.
The brown grease is different from "yellow grease," which is just used deep-fry oil. Restaurants can sell or at worst give it to biodiesel makers (San Francisco already has a yellow grease to biodiesel program). The brown grease is pure rancid waste. Restaurants are required to collect it in grease traps to keep from clogging sewer pipes, but then they have to pay for collection and it ends up in landfills. The financial incentive is cheat a little and put some down the drain. But if the city collects it and makes use of the grease, the incentive is for proper disposal.
San Francisco is using state and federal grants to build its small biodiesel plant near the city zoo and in return for the grant will release all of its data about what works and what doesn’t– an "open source toolkit" for other cities.
The program won’t extend to home grease, but it’s a start. And the city is hoping restaurants will use only vegetable oil for frying, to cut down on animal fat like bacon grease, and hydrogenated oils in the sludge.
Commenters on the San Francisco Chronicle website groused today about the cost per gallon, and the energy used to produced fuel from brown grease. They’re missing the point. You don’t compare the energy cost to making regular diesel from light, sweet crude oil. Compare it to the environmental and monetary cost of making diesel from tar sands or shale oil or Ecuadoran heavy oil. And the cost per gallon is a better use of funds than filling landfills or grinding grease out of sewer pipes.
My only question: Can they make it so the vehicle exhaust smell like bacon?