Getting food out of the trash: It's what New York City’s former mayor Michael Bloomberg called recycling's last frontier.
But even as more Americans sort paper from cans and bottles, and recycling rates climb, food collection has lagged. Only about 170 communities nationwide pick up homes' scraps to turn them into compost.
Discarded food can return nutrients to the soil and help Americans cut down on pollution and fertilizer use, but in landfills, it takes up space and contributes to pollution.
On Earth Day, here is a look at some wasted opportunities for food composting and why it matters.
— Americans created 251 million tons of garbage in 2012, most of it organic material. Food waste accounted for 28 percent of the total.
— Of the 87 million tons of garbage that was recycled or composted in 2012, only 2 percent was food waste. By contrast, paper represented about 51 percent and yard trimmings about 22 percent.
— Of the 35 millions tons of food that was thrown away in 2012, more than 96 percent went to landfills. By contrast, some 60 percent of yard trimmings was composted.
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— About 3,120 community composting programs of all sorts existed in 2012, down from 3,227 in 2002.
— Food discarded in landfills creates methane, a greenhouse gas. Landfills accounted for more than 20 percent of methane emissions in the U.S.
— Since beginning mandatory compost collection in 2007, San Francisco has cut what it sends to landfills in half. Its goal: Zero waste by 2020.
— Seattle, which this year banned food from residential and commercial garbage, had been sending 100,000 tons of waste a year to a landfill in eastern Oregon. It hopes the new law will cut that amount by 38,000.
— New York City has been burying 1.2 million tons of food waste each year at a cost of $80 per ton. Its compost pilot program is now collecting food scraps from 100,000 households and expects to add an additional 40,000 households this spring.
— Parched California and other drought-stricken areas could save water. Studies show that increasing the organic matter on one acre of land by 1 percent saves 16,500 gallons of water a year.
Sources: U.S. EPA, San Francisco Department of Environment, BioCycle magazine, New York City Department of Sanitation, Seattle Public Utilities, Marin Carbon Project