Food Compost: There’s Gold in Them-Thar Green Bins

compostMy desk is at the front of my house, right by a street-facing window, so I keep an unintentional vigil on my San Francisco street. Wednesday is garbage day on my block and at around four o’clock this afternoon, I noticed something unusual: the compost collection truck, coming through a few hours later than normal. But then I remembered that today is the first day in which composting–not just yard waste, but also food–in San Francisco is mandatory. These drivers are extra busy.

Though it might sound radical to someone from outside the Bay Area, San Francisco’s new composting law doesn’t exactly mark a sea change for many residents or businesses. The city already diverts 72 percent of materials away from landfills, including about half of its food waste.

That amounts to 500 tons of food (up from 400 tons before the law passed) streaming into the organic waste annex at the SF city dump each day, according to this NPR story. There, it is converted into compost and sold to local farms and vineyards , where it fertilizes food crops that come back to San Franciscans as food and wine. Ah, the circle of life.

To farmers, that compost is gold. To waste management companies, diverting food from landfills saves space and reduces the amount of methane gas that is emitted from the landfill. So it all sets up a nice win-win.

But as I learned at the Waste Expo conference this summer, compost isn’t the only valuable commodity we can derive from our leftover Chinese take-out. It can also be turned into energy. Across the bay from San Francisco, the East Bay Municipal Utility District uses anaerobic digesters to convert the methane formed during the digestion process of food and biosolid waste (poop, basically) into renewable energy, for example.

Either way, commercial entities can save money by diverting food waste because it lowers their waste disposal fees, which are generally based on weight (and food is the heaviest part of most waste streams). After running a waste audit in Ohio, the Kruger supermarket chain found that nearly 60 percent of its waste stream was compostable. It then ran a four-month pilot program at 24 of its Ohio stores, during which compostable material was separated from non-organic waste. The company’s findings, further detailed in this case study published in BioCycle magazine , showed that separating food waste was economically feasible, despite the relatively cheap garbage collection rates Kroger pays in that part of the country. Based on this, the practice could be a major money-saver for grocery stores in places where landfill tipping fees are highest.

But more important than that, Kroger’s willingness to test the waters for composting has helped fuel initiatives by the Ohio EPA and the Ohio Grocers Foundation to build out an infrastructure for high-volume composting systems in that state. Many Ohio facilities that used to only accept yard waste have now been licensed to compost food waste, as well. And aside from creating compost, food waste composting facilties will also start using anaerobic digesters to create renewable energy.

So  even though it’s the first city in the country to make composting mandatory, San Francisco isn’t the only part of the country that is uncovering the value in diverting food waste. Hopefully more municipalities will start to encourage great food waste diversion, as well, in order to grab the gold that is othewise wasted in landfills.

Freelance writer Mary Catherine O'Connor finds that a growing number of companies are proving the ways that they can make good financially, socially and environmentally (as the triple bottom line theory suggests).With that in mind, she contributes to Triple Pundit, as well as to Earth2Tech and other pubs focused on sustainability. She also writes The Good Route, an Outside Magazine blog that addresses the intersection of sustainability and the active/outdoor life.To find out more, or to reach her, go to

6 responses

  1. I’m an American living in Ireland and composting isn’t mandatory (I don’t believe) but is a widespread practice. I speculate that many people compost kitchen waste here due to cost savings. In Dublin at least, single stream recycling collection is free and easy. Many homes have 3 bins: gray for general waste, green for recyclables and brown for compost. For those living in an area where bins are not feasible (e.g. apartment blocks, urban homes, etc.) recycle bags are mailed free of charge and rubbish tags must be applied to all waste bags, which essentially amounts to a tax. On my street, we use the bags so unfortunately we don’t have a brown bin. Instead, I’ve made a small compost pile in the shared back garden of our cluster of houses and we have nearly eliminated all general waste. In the two months that we have lived here, we’ve only purchased one rubbish tag for a very small bag of trash when we first moved in that probably could have been eliminated, except I had not yet started the compost pile.

    Essentially we produce nearly zero waste and the compost pile was very easy to setup in even a tiny space. My only problem now is what to do with meat scraps and bones (not compostable): become a vegetarian I guess? Any suggestions?

  2. James: Well, of course! Becoming a vegetarian is the obvious answer! But a more difficult choice in practical matters in Ireland, perhaps, than here in Northern California. Then again, I wouldn’t have guessed that Dublin would be on the cutting edge of recycling, so I clearly have misconceptions.
    Thanks for the response and for sharing your experiences. It’s inspiring.

  3. Your mention of anaerobic digestion in the East Bay is key on this issue. If organic wastes of any type are gathered, it is far better to extract their energy value than to “compost” them. Composting simply wastes the energy value in the waste and makes a fertilizer that has a huge carbon footprint because of the methane emissions it entails. Waste energy is a terrible thing to waste. It should be put into either an anaerobic digester or a fast pyrolysis sysem.

    1. An interesting note: the East Bay system operated by EBMUD is having trouble with its biosolids-contaminated wastes (poop plus food waste). Perhaps we biodigest first, then fast pyrolize, this valuable but troublesome energy source? And send pure-food waste through from the biodigester to compost facilities without pyrolysis… compost+charcoal=damn good soil, if the ratios are right (a good start towards terra preta soils).

      I really want to see this happening on the east coast – I live in Asheville, NC, which is a pretty progressive little city with a lot of work to do on waste, despite its efforts. Anyone got any resources to check out/people to talk to/sites to recommend, etc?

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