New Yorkers already have blue and green bins for recycling glass, metal, paper and plastic. But now brown bins for organic waste are starting to appear all over the city. These plastic totems are part of the city’s multimillion-dollar campaign to cut down on greenhouse gas emissions and reliance on landfills, and to turn food scraps and yard waste into compost and, soon, clean energy.

In the 19th century, the city had a simple method for dealing with organic rubbish: It enlisted scavenging swine to nose through the gutters for leftovers. Now, the city is employing the primal chemistry of decay.

About 14 million tons of waste are thrown out each year. It costs the city almost $400 million annually just to ship what it collects from homes, schools and government buildings (by rail, barge or truck) to incinerators or landfills as far away as South Carolina. (In addition, dozens of private companies put trucks on the road to take away refuse from office buildings and businesses.)

The largest single portion of the trash heap is organics, or things that were once living. That apple core, that untouched macaroni salad, that slice of pizza and the greasy paper plate it was served on are heavy with moisture, which makes shipping expensive. As they decompose, they release methane, a greenhouse gas.