Pet Poop: Experts Explore Its Energy Potential

From: Grist Magazine <www.grist.org>
2/23/06

Old Dog Poop, New Tricks

San Francisco looks to harness the power of pet poop

Renewable energy is the sh*t. No, really. San Francisco Bay Area cities are
aiming to generate no trash by 2020, and nearly 4 percent of San Francisco's
residential waste is animal excrement. What to do with the doo? Turn it into
methane and heat your home or cook your meals with it! (Um, ew.) In the next
few months, a San Francisco sanitation company will be collecting feces at a
busy dog park -- no doubt employees are jostling for the assignment -- and
sending it to be digested by hungry bacteria. The resulting methane could
theoretically be used in any natural-gas system. Some officials hope to see
methane digesters in individual homes within a few years. While it's a
relatively newfangled notion in the United States, some European countries
already process poo into energy.
straight to the source: San Francisco Chronicle, Carolyn Jones, 21 Feb 2006

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/02/21/MNGUIHBUPP1.DTL&hw=dog+waste+energy&sn=001&sc=1000
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POWERED BY POOCHES
Rather than let pet dung go to waste, experts explore its energy potential

Carolyn Jones, Chronicle Staff Writer
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."
E-mail Carolyn Jones at carolynjones@sfchronicle.com