Nav: Home

Composting food waste remains your best option, says UW study

December 16, 2015

Many people compost their food scraps and yard waste because they think it's the right thing to do.

A new University of Washington study confirms that sentiment, and also calculates the environmental benefits associated with keeping these organic materials out of landfills.

The biggest takeaway for residents of Seattle, San Francisco and other places that offer curbside compost pickup is to take advantage of that service -- and pat yourself on the back for using it.

"You should definitely pay attention to where you put your food waste, and you should feel good you live in a place where compost is an option," said paper author Sally Brown, a UW research associate professor of environmental and forest sciences.

Food waste in particular generates a significant amount of the greenhouse gas methane when it's buried in landfills, but not so when composted. U.S. cities and counties that offer composting prevent otherwise trash-bound food scraps from decomposing in landfills and generating methane -- and they get a significant carbon credit as a result.

"That gives municipalities a big incentive to do this," Brown added.

Brown's study, appearing in the January 2016 issue of Compost Science & Utilization, analyzes new changes to a U.S. Environmental Protection Agency model that helps solid waste planners estimate greenhouse gas emission reductions based on whether materials are composted, recycled, burned or thrown away.

With compost, the model calculates how much methane is produced over time in landfills as organic materials decay. It also considers how much methane from landfills is currently captured in collection systems verses being released into the atmosphere.

The results are overwhelmingly in support of composting food waste rather than sending it to landfills.

"Putting your food waste in the compost bin can really help reduce methane emissions from landfills, so it's an easy thing to do that can have a big impact," Brown said.

In the U.S., about 95 percent of food scraps are still thrown away and eventually end up in landfills. The scenario is better for yard waste -- grass clippings, leaves and branches -- with more than half diverted to compost facilities instead of landfills.

Brown's analysis found that the benefits of composting yard trimmings is less clear on paper, because the speed that the material decomposes depends on location and season. For example, yard waste in Florida in December will likely break down a lot quicker in landfills and create more methane gas than the same amount of yard waste in Minnesota during the same month.

Food scraps, alternatively, decay and start producing methane at about the same rate in all regions. The content of food waste is relatively consistent across seasons and locations, and the same can be said for conditions in landfills. While it may be snowing in Minnesota, the temperature within the landfills is likely to be over 70 F.

The variation for yard trimmings makes it hard for the Environmental Protection Agency model to cast a broad generalization of the material's methane production, and thus the overall environmental cost and benefit of composting verses landfilling, Brown said.

But composting food scraps and woody yard materials together makes sense because dryer, high-carbon, yard trimmings mix with soggy food scraps to create ideal conditions for the compost process, she added.

Seattle and King County were among the first municipalities nationwide to adopt food waste composting and curbside pickup. Other leaders include San Francisco, New York City and the states of Vermont and Massachusetts.
-end-
The study was funded by the King County Wastewater Treatment Division and the U.S. Environmental Protection Agency.

For more information, contact Brown at slb@uw.edu or 206-755-1396.

Related paper:http://www.tandfonline.com/doi/full/10.1080/1065657X.2015.1026005#.VnGirUorKK4

Related column by Brown in BioCycle:http://www.biocycle.net/2014/09/18/connections-a-better-warm/

University of Washington

Related Methane Articles:

Microorganisms reduce methane release from the ocean
Bacteria in the Pacific Ocean remove large amounts of the greenhouse gas methane.
Origin of massive methane reservoir identified
New research provides evidence of the formation and abundance of abiotic methane -- methane formed by chemical reactions that don't involve organic matter -- on Earth and shows how the gases could have a similar origin on other planets and moons, even those no longer home to liquid water.
Methane not released by wind on Mars, experts find
New study rules out wind erosion as the source of methane gas on Mars and moves a step closer to answering the question of whether life exists on other planets.
Unexpected culprit -- wetlands as source of methane
Knowing how emissions are created can help reduce them.
Methane-consuming bacteria could be the future of fuel
Northwestern University researchers have found that the enzyme responsible for the methane-methanol conversion in methanotrophic bacteria catalyzes the reaction at a site that contains just one copper ion.
More Methane News and Methane Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Erasing The Stigma
Many of us either cope with mental illness or know someone who does. But we still have a hard time talking about it. This hour, TED speakers explore ways to push past — and even erase — the stigma. Guests include musician and comedian Jordan Raskopoulos, neuroscientist and psychiatrist Thomas Insel, psychiatrist Dixon Chibanda, anxiety and depression researcher Olivia Remes, and entrepreneur Sangu Delle.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...