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Thursday, June 19, 2014

Sink Disposal Vs. Garbage Can: What To Do With Non-Composted Food Waste?

Garbage disposal (InSinkErator)

For those who don’t have the advantage of a special composting program, or the ability or desire to compost, what is next best? It turns out that the answer is a complicated one. (InSinkErator)

There’s little disagreement that composting food waste is the gold standard when it comes to environmental sustainability.

In New York, last year’s pilot program to bring curbside food waste recycling to 30,000 households in the Bronx, Brooklyn and Staten Island is being expanded to 70,000 new homes in Queens and Brooklyn. All of that food waste will be composted, reducing the annual amount of trash hauled to landfill by more than a million pounds a year.

But for those who don’t have the advantage of a special program, or the ability or desire to compost, what is next best? It turns out that the answer is a complicated one. To sort it out, Here & Now’s Robin Young talked to Stefan Grimberg, chair of the Department of Civil and Environmental Engineering at Clarkson University in Potsdam, New York.

According to Grimberg, Americans have many options when it comes to dealing with their food waste, and the best choice varies by household, depending on factors like how far they live from landfill, what kind of digesters their waste water treatment plant uses, and whether their local landfill traps its methane gas.

“The challenges are to know where and how the waste water is treated.”
– Grimberg

For example, if 30,000 homes used a disposal to get rid of their food waste rather than their garbage can, the global warming potential of disposing food waste would be reduced by 1.9 million kilograms of carbon dioxide. This is the equivalent of not driving 4.6 million miles. The catch: everything about these disposals and the waste water system would have to be designed for maximum environmental impact.

A “good” system, by Grimberg’s standards, uses the organic material, treating it in an anaerobic digester and converting it into bio-gas. This product can be used as a heat and power generation system, which would off-set the plant’s electricity demand. But this system, despite its environmental friendliness, is not used in all waste water treatment plants.

“The challenges are to know where and how the waste water is treated,” Grimberg explained. “If it goes in a waste water treatment plant which has poor treatment, then it’s an extra load to the plant, extra electricity use, extra energy use, and then potentially discharge into an ecosystem, which is an extra load to the environment.”

And further, many waste water treatment plants dispose their bio-solid end product into landfills; thus, the food waste ends up in the landfill even if consumers send it down their drains. Not only is the potential energy wasted, but also methane — 20 times more potent a greenhouse gas than CO2 — is released into the air as the waste decomposes. Some “modern” landfills, Grimberg says, collect the gas in a manner similar to the “good” waste water treatment plans.

Still, it varies by the community. In some cities, sink disposals are a justifiable alternative to composting food waste. But Grimberg maintains that composting is the most universally “environmentally sound” way to dispose of food waste. Now, cities can help to centralize the process, as they are now in New York, allowing more people to efficiently get rid of their food waste without the negative environmental impacts of other disposal methods.


  • Stefan Grimberg, chair of the Department of Civil and Environmental Engineering at Clarkson University in Potsdam, New York.

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  • http://neilblanchard.blogspot.com/ Neil Blanchard

    This is a great discussion! Thank you. Composting can and should be paired with leaves and grass clippings, etc. This also saves buying artificial fertilizer, which causes climate change and pollution. Compost actually improves the soil, and it costs nothing, and reduces pollution.

  • Jodi Smith

    It’s likely that most cities do not have the ability to properly process the run off from the garbage disposals.
    Also, I’ve had more than one plumber tell me that garbage disposals are their biggest moneymakers. Garbage disposals cause a lot of drainage issues, especially when people do not use them properly and try to cram too much or the wrong thing down them. We got rid of our garbage disposal years ago.

    • Kendall Christiansen

      in fact, the trend is the opposite: internationally cities with limited prior experience are lifting restrictions and adopting disposers as essential component of their tool-kits, in some cases via building code mandates and/or incentive programs. In US, 50 million+ installed; 80% of California households have at least one – with nearly major and moderate-size cities having capability and capacity to produce clean water, biogas and fertilizer products from wastewater, including food scraps pulverized via a transport and transported easily underground.
      Plumbers like toilets for the same reason; people learn over time how to use their disposers effectively, but current-generation models are improved to handle ALL types of food scraps more quietly and efficiently, making them capable of eliminating food scraps from residential kitchens.
      Several demonstration projects are underway to assess their efficacy – including in Boston.

  • Collin F

    More relevan to the Boston-area WBUR audience: are boston’s wastewater treatment plants on Deer Island capable of this?

    • Kendall Christiansen

      absolutely; in fact MWRA in process of adopting policy statement acknowledging the beneficial use of food waste disposers, and demonstration project underway in Roxbury with support of Mayor’s Office. Most cities have water resource recovery facilities (it’s not “wastewater” anymore) with similar capabilities of producing clean water, biogas and fertilizer products; in some cases, also accepting/managing commercial/industrial food scraps delivered via truck, bypassing the initial phase that separates organic solids from water.

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