According to a popular bumper sticker, ?sh*t happens.? It also happens to have the power to heat homes, cook meals and generate electricity. At least, that is the hope of San Francisco and other cities in the Bay Area, which are looking at ways to recycle and reuse animal waste as part of their mission to stop sending trash to landfills by 2020.

Converting Animal Waste Into Fuel
San Francisco has become the first city in the United States to consider converting pet feces into methane that can be used for fuel, according to the San Francisco Chronicle.

If the experiment goes well, it won?t be the last.

"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, in an interview with the Chronicle. "That's really beginning to be looked at as a nightmare."

Keep Animal Waste Out of Landfills
A lot of it is goes into landfills. In San Francisco, for example, animal feces accounts for nearly 4 percent of the city?s residential waste?almost as much as disposable diapers, another landfill nightmare. Tossed into landfills inside plastic bags, animal waste becomes a nearly permanent part of the landscape for generations. For a city that is striving to eliminate its use of landfills, finding a better way to manage animal waste is an important issue.

Pet feces that is not tossed out is left on the ground, where it dissolves and flows untreated into the water table or San Francisco Bay.

Some is inadvertently collected along with yard waste and tossed into compost bins, a dangerous practice because animal waste is full of pathogens. Until pet feces can be converted into methane as a cost-effective energy alternative for communities, waste experts say the most eco-friendly way to dispose of animal waste is to flush it down the toilet so that it can be treated in the sewage system.

A Strategic Plan to Turn Animal Waste Into Methane
The city has asked Sunset Scavenger, a subsidiary of Norcal Waste, the company that collects most of the waste in San Francisco and a dozen other Northern California cities, to find a way to use dog and cat droppings instead of tossing them into landfills or leaving them unmanaged to pollute the water.

"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, in an interview with the Chronicle. "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."

Norcal plans to place biodegradable bags and dog-waste carts in one of the city?s busiest dog parks, collect the waste, and toss it into a methane digester?a low-tech machine that uses bacteria to convert animal waste to methane in about two weeks. After that, the methane can be used to power anything that normally runs on natural gas, such as a kitchen stove or a heater.

Many Nations Already Use Animal Waste for Fuel
Converting animal waste to fuel may be a new concept for cities in the United States, but the strategy is already well established in several European countries and a number of developing nations, not to mention a handful of U.S. dairy farms that convert waste from dairy cattle into methane that powers farm machinery and saves the farmers thousands of dollars every month.

While it is conceivable that home methane digesters could catch on as an alternative source of household energy, the idea probably isn?t practical. Most individual households don?t produce enough organic waste, such as food scraps and animal feces, or produce it consistently enough to provide a reliable source of energy for an entire home. City and state governments are another matter.

"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," said Fernando Berton of the California Integrated Waste Management Board. "If we can turn something from a waste into a resource, we should be doing that."