Though we've talked briefly about this before [2], ABC News recently went into a lot more detail about the plan. They interviewed Robert Reed, an employee of Norcal Waste, the trash-hauling company that went to the city and suggested converting the organic waste into energy.
Norcal already seems to have a nice track record for efficiency: the company provides fertilizer for local organic farms and vineyards made from 300 tons food scraps a day. That's over half a million pounds of food refuse not rotting in city dumps but instead being put to excellent use. Over a year's time, that totals over 230 million pounds -- or almost 110,000 tons.
According to Norcal, the high protein mass in pet poop makes for a good energy output. Combined with garbage like cantaloupe skins, broccoli, and Brussels sprouts, the poop mixture provides enough calories to procure fifty gallons of fuel for each ton of the garbage mixture, which is known as "manufactured biomass." Eighty tons of manufactured biomass could produce enough energy to run a thousand homes -- which wouldn't be hard to find, considering the sources of garbage from which Norcal already collects. Mentioned in the article specifically are restaurants and doggy daycares.
So how does the conversion occur?
The biomass converts to methane gas via a machine called a digester [3]. And apparently this is not an uncommon piece of hardware. References to this machine are all over the web, notably in an Argentinean article from December, 2004, that talks about a man who made his own digester [4] -- over thirty years ago! You can find fantastic information on digesters here [5].
Thanks to a combination of a liberal government and a dense pet population, San Francisco seems destined to realize a novel and wonderful form of natural energy. If this new source of both energy and jobs works, I am hopeful that the rest of the country will take heed to notice.
