Composting turns rotting garbage into a valuable soil enhancer that helps plants thrive. Farmers call it “black gold.”
And now more cities are implementing curbside composting to help them meet their sustainability goals. New York is currently rolling out a mandatory composting program that will soon be effect in Brooklyn and throughout Manhattan by next year. Washington, D.C. and Chicago are piloting curbside composting programs, and Seattle and San Francisco have been successfully composting residents’ food scraps for years.
But you don’t have to wait for a city-wide program to begin composting in your backyard to taking food scraps to a community bin.
“Don’t be afraid of it. It’s relatively easy. It’s not without its missteps but those are easily learned and corrected,” says Bob Rynk, lead author of The Composting Handbook and a professor emeritus at SUNY Cobleskill.
What happens in a compost pile?
Food turns into compost through the hard work of small microorganisms like bacteria, fungi, and protozoa.
“When you have a compost pile, you become a microbe farmer. You’re managing microbes,” says Rhonda Sherman, a composting expert at North Carolina State University. “And what do microbes need? They need the same things we do. Which is air, water, food, shelter.”
On a small scale, in your backyard or neighborhood, a compost pile should consist of three things: food scraps, water, and dry, woody material like yard trimmings or raked leaves.
Yard trimmings are frequently referred to as “browns” and are high in carbon. Food scraps are called “greens” and are high in nitrogen. A compost pile should typically have twice as many browns as it does greens.
Aside from preventing a pile from turning into a sloshy mess, browns are bulkier and create space for oxygen to move throughout the pile. That oxygen helps tiny microbes decompose food waste through a process called aerobic digestion.
In landfills, deep piles of trash prevent oxygen from reaching decomposing food, and it’s instead broken down by microbes that can survive without air. The anaerobic digestion practiced by those microbes produces methane.
In contrast, as aerobic microbes break down waste—”first, easier sugary compounds, and then proteins and fats, and then finally fiber,” says Rynk—they emit carbon dioxide, which is also a greenhouse gas, but less potent than methane.
The microbes also give off heat, and in a large, well-managed pile, that heat can reach over 130 degrees Fahrenheit, enough to kill pathogens.
The fresh compost left after several months is in a slower state of decomposition; it’s rich with microorganisms and nutrients such as nitrogen, phosphorus, and potassium.
How to make a successful pile
At home, you should stir or mix the pile periodically and keep it damp. Both those steps will speed up the decomposition process. The stirring allows oxygen to reach all the nooks and crannies, and the dampness assures survival of the microorganisms, which need moisture to live….