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San Francisco Chronicle - Tuesday, February 21, 2006
In the future, we might be heating our houses with dog poop.
As San Francisco, Oakland and other Bay Area cities strive to reach self-imposed goals of keeping every bit of trash out of landfills by 2020, even animal waste is being scrutinized to see how it might be reused or recycled.
And so San Francisco has become the first city in the country to consider turning Fido's droppings into methane, which can heat homes, cook meals and generate electricity.
"Poop power? Yes, it's possible to produce electricity, natural gas and even fuel from Rover's poop and other waste material," said Robert Reed, a spokesman for Norcal Waste, which carts away the waste San Francisco, San Jose and a dozen other Northern California cities generate. "There are a lot of bugs to work out, steps to figure out, costs to be considered, but we are beginning to talk to the city about it and look into this area more actively."
Animal feces make up nearly 4 percent of San Francisco's residential waste -- nearly as much as disposable diapers -- so it is a significant stumbling block to cities reaching their landfill goal.
"American dogs and cats produce 10 million tons of waste a year, and no one knows where it's going," said Will Brinton, a scientist in Mount Vernon, Maine, and one of the world's leading authorities on waste reduction and composting. "That's really beginning to be looked at as a nightmare."
Dog and cat waste usually ends up in a landfill, where it's mummified for generations in plastic bags. If it's not tossed out, it's left where it falls and dissolves into the ground, where it flows untreated into the water table or the bay. Or it's scooped up with yard waste and tossed into the compost bin -- which is a no-no, because animal waste is full of pathogens.
So San Francisco has asked Sunset Scavenger, a subsidiary of Norcal, to find a use for it.
In the next few months, Norcal hopes to place biodegradable bags and dog-waste carts in Duboce Park, one of the city's busiest dog parks.
The waste will be collected and tossed into a contraption called a methane digester, which is little more than a tank in which bacteria chew on poo for about two weeks to create methane.
The methane can be piped directly to a gas stove, heater, turbine or anything else powered by natural gas.
The idea isn't so far-fetched. Several European countries, developing nations elsewhere in the world and a smattering of American dairy farms already convert animal waste into energy.
Straus Family Creamery in Marin County installed a methane digester in 2000, and it's working great, company officials said.
In a 2004 report prepared for the California Energy Commission, the creamery's manure-to-energy process met or exceeded expectations. The dairy uses the methane to power the plant, saving Straus thousands of dollars a month in energy bills.
There are a few potential glitches, however.
Most households don't produce enough food scraps, animal waste and other organic matter to power an entire home. And most households don't produce waste at a rate consistent enough to be a reliable energy source.
Another problem is that the gas in the methane digester will probably contain small amounts of other gases, which will diminish the methane's efficiency.
But with a few technological tweaks, methane digesters could be used in individual homes within the next few years, said Fernando Berton of the state Integrated Waste Management Board
"You've got solar panels on homes. Why not home-based anaerobic digestion processes?" he said.
But it's more likely that cities, not individuals, will use methane digestion to produce energy that would be piped to homes, he said.
The state's Integrated Waste Management Board is also eager to explore methane digestion. The board is working with a UC Davis biogas lab to study further uses for methane digestion, and the state is giving out methane digestion grants to dairies and farms.
"California sends 40 million tons annually to landfill, and over half of it is organic in nature. It makes sense to look at the alternatives," Berton said. "If we can turn something from a waste into a resource, we should be doing that."
Dog owners seem to be open to recycling their pets' waste. At Bernal Heights dog park in San Francisco, trash cans can overflow with plastic dog-poop bags on a busy weekend.
"It bugs me that I'm sending a plastic-wrapped time capsule of my dogs' stool samples to the landfill every day," said Robert Picciotto, a high school English teacher who regularly walks his setter, Jesse, at the park. "Apparently, that's going to be my shout-out to future generations."
In Oakland, the problem isn't animal waste in landfills, but in the water supply. It seeps into creeks, down rain gutters and flows untreated into the bay.
"It's a big water-quality thing. Dog poop gets into the water, and sometimes we have to close beaches because of it," said Becky Dowdakin, solid waste and recycling supervisor for the city of Oakland. "That's a really important reason to clean up dog poop."
Until turning all those droppings into methane is feasible, the most ecologically sound way to dispose of it is to flush it down the toilet, where it can be treated in the sewage system, waste experts said.
There is some debate among pet owners and environmental groups about tossing pet waste into backyard compost bins. Most scientists warn against it because the compost does not heat up enough to kill the pathogens such as E. coli -- which could then be transmitted to people if the compost is used in a vegetable garden.
Industrial composters, used by some cities to dispose of green waste and kitchen scraps, are a better option. They can reach temperatures of about 160 degrees, hot enough to kill even the most stubborn pathogen.
High-heat techniques also are an effective way of converting animal waste to methane, but it's less appealing than methane digestion because it produces significant air pollution, experts said.
So that leaves methane digestion as the most promising solution. But it won't take off until it makes sense economically.
Landfills remain relatively cheap -- it costs only $40 per ton to dump garbage into a landfill -- so although each Californian sends more than 5 pounds of trash to a landfill daily, it's still among the cheapest options in the short run.
What's more, natural gas and electricity remain fairly inexpensive. So although Bay Area residents may someday heat their homes with dog droppings, the rest of the state isn't about to jump on that bandwagon, Berton said.
"We're very supportive of what San Francisco is looking to do," he said. "Maybe it'll be a test case. But as far as the rest of the state goes, I think we're still a ways off."
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