SAN FRANCISCO - City officials are hoping to harness the power of dog doo. San Franciscans already recycle more than 60 percent of their garbage, but in this dog-friendly town, animal feces make up nearly 4 percent of residential waste, or 6,500 tons a year — nearly as much as disposable diapers, according to the city. Within the next few months, Norcal Waste, a garbage hauling company that collects San Francisco's trash, will begin a pilot program under which it will use biodegradable bags and dog-waste carts to pick up droppings at a popular dog park. The droppings will be...