On a bright, windy fall day, a dump truck full of dried leaves, overgrown squash, chestnuts and other sundries of garden and kitchen waste arrive at the City of Boise’s Twenty-Mile South Farm.
The truck has collected the materials from green bins from homes around Boise and is dropping its contents so it can be piled into windrows and left to break down.
“Every year, we process over 30,000 tons of organic material here at Twenty-Mile South compost facility,” said Lisa Knapp, head of Boise's residential composting program.
In 2014, Ada County did a study and found that a high percentage of garbage going to the landfill was organic material. With limited space, refuse is smashed down and green material breaks down in an environment without oxygen.
“It's buried every day. And that produces methane, which is a very potent greenhouse gas,” said Knapp
Methane is 20% more potent than carbon dioxide at trapping heat in the atmosphere. If those grass clippings, banana peels and apple cores are redirected into backyard or city compost bins they break down in an organic cycle.
“Composting is the human engineering of, of a natural process that happens every day on the forest floor, when organic material breaks back down into its original components,” Knapp explained.
So in 2016, the city launched a composting program to help redirect part of the waste stream.
The Environmental Protection Agency reports 24% of municipal solid waste is food waste and that wasted food accounts for 58% of methane emissions from municipal solid waste landfills.
Cities, counties and states can launch composting programs, but Brenda Platt who directs the Composting for Community project for the national nonprofit the Institute for Local Self-Reliance, says it can happen on many levels.
“It can be as small as a bin in your backyard or a worm composting bin in a classroom all the way to large industrial sites. And then in between are farmers and municipal sites.”
If you have a yard and space, composting is relatively simple with several different techniques to make food scraps into rich soil amendments. The most common is hot composting, where gardeners pile organics in a pile or a simple bin.
“It's not rocket science. There's just a few things to know, like balancing your browns and your greens, and the microbes to make them happy,” said Platt.
The browns are things like leaves or wood chips, basically things that contain carbon. They are mixed at a higher ratio to greens, which are fresh food scraps, grass clippings. Greens have high nitrogen rates. The pile will need to be turned to increase oxygen flow and kept moist. After a few months, a rich soil remains.
There are other techniques too including worm bins and fermenting or bokashi systems that allow meats and dairy to be broken down. There are now electric composters that can fit on a kitchen countertop and are an option for city dwellers who don’t have land.
Platt said the dirt from food waste is a better soil amendment than anything you can buy and will help grow stronger flowers and vegetables.
It is true that composting emits carbon dioxide, which is a greenhouse gas, but Platt says using the compost to grow new, healthier plants becomes a net win.
“You're growing the plants as the plants grow. They're absorbing carbon dioxide. Then at the end of their cycle, so then you’re producing compost. It's going back into the ground. So it's a net carbon climate win. It's a win-win for the climate,” Platt said.
Lisa Knapp with the City of Boise says every year its facility avoids emitting about 5,000 metric tons of carbon dioxide equivalent from the atmosphere. That’s about the same as getting rid of about 11-hundred gas-powered passenger cars off the road for a year.
“Everything that we put into our trash bin that's organic, that was, could have, could have been composted instead of going to the landfill is making an impact. So it's just as important as saving water, just as important as turning off the lights,” Knapp said.
So next time you think about throwing away an orange peel or watermelon rind, you could cut down on methane emissions by making it into compost instead.
