Feb. 23, 2006 — San Francisco is hoping to convert its dog dung into energy that may be able to power everything from an electricity-generating turbine to a home stove, according to Norcal Waste Systems Inc., which oversees garbage collection, recycling and disposal for San Francisco and several other Northern California cities.

San Francisco is believed to be the first U.S. city to explore the energy potential of dog feces. A pilot test program may begin within the next few months.

"The city of San Francisco has a goal of 75-percent landfill diversion by 2010 and zero waste to landfill by 2020," said Robert Reed, Norcal's spokesman. "According to a recent waste characterization study, 3.8 percent of garbage from residential collections was animal feces — mostly from dogs and cats, although other animals could have been represented."

Tony Bennett may have left his heart in San Francisco, but the city's estimated 240,000 cats and dogs leave calling cards of their own. Norcal has decided to focus on dog doo because it is easier to collect, since dog owners frequent certain parks and could dispose of their pets' waste in controlled receptacles.

"It's a tradition for many people to grab a newspaper, their dog's leash and a plastic bag before going on a walk," Reed told Animal Planet News. "They use the plastic bag to pick up his little gift."

In the future, the plastic bags likely will be made out of biodegradable materials so they won't gum up the process or have to be separated from their pungent contents. If the test phase moves forward, Norcal hopes to put a collection bin in Duboce Park, a popular San Francisco park for dog walkers. Once collected, the poo would be placed into a methane digester, which is sort of like a compost bin for dung.

Similar to plant composting, methane digesting allows bacteria to break down the initial raw product. Animal feces naturally contain microbes called methanogens, which live off hydrogen and carbon dioxide that are produced by other microbes. In addition to being in animal waste, methanogens are in many other environments without free sources of oxygen, such as mucky swamps and marshes, sewage sludge and the guts of termites.

The methanogens use hydrogen as a source of electrons for breaking down carbon dioxide into microbial food. Methane gas is a byproduct of the process. The resulting biogas is energy gold. It can be piped to stoves, turbines, heaters, and other equipment that may run on natural gas.

William Brinton is president of Woods End Laboratories, Inc., a Maine company that specializes in analysis of compost and other waste. He told Animal Planet News that he supports San Francisco's animal waste to energy conversion goals. Biogas is already being produced and used in several European countries, on farms in the United States and Canada, and in third world countries.

"Often third world users just put animal waste in plastic bags that are placed into holes in the ground," Brinton said. "Straws or tubing poked into the bags divert the gas into homes. You can then light the gas and there's your heat."

Brinton said ground limestone, buffering agents or acids "to kick the natural process up a notch" can be added to methane digesters, which may also be temperature-controlled to speed up the process. Dung digesting occurs faster in a warm environment.

"What's wonderful about dog manure is that it is very high in energy because of the rich diets we feed our pets," Brinton said. "We anticipate that it will yield as much energy as food scraps, which can produce $20 to $30 of energy per ton of waste."

As for the odor associated with dog doo, Brinton assures there is no need for nose plugs.

"The resulting gas does not have much smell," he said. "Sometimes there is a slight egg-like sour odor in the containerized process, but this can be easily filtered out."