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FoodShare Composts: Closing the Loop
Composting is a vital part of the urban agricultural system. By composting our plant wastes and then using the compost to improve the garden's soil, we are closing the loop between production, consumption, and waste and ultimately can reduce our ecological footprint.
In urban areas plant wastes are concentrated and available. Instead of being sent to a landfill, those “wastes” can be turned into rich, fertile soil. Composting gathers plant wastes and through a process of controlled decomposition turns them into soil in a matter of weeks or months. This soil is so rich and well textured it eliminates the need for chemical fertilizers, and can greatly increase the efficiency of irrigation systems.
| The decomposition process generates significant heat--the compost thermometer shows almost 150 degrees F in early April |  |
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At Field to Table, FoodShare has a mid-scale compost processing operation. In this operation Focus on Food youth participants, volunteers, and staff learn about composting. They all help to process the food waste from our catering operations and food that’s not good enough to be put into the Good Food Box into rich, fertile soil. With a generous grant from the Toronto Atmospheric Fund we’ve recently developed a guide to mid-sized composting operations to share our experience with others interested in mid-scale composting. It is available directly from FoodShare. |
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| Toronto's Mayor David Miller takes a turn at Field To Table's compost while compost master Mike Nevin looks on. | |
Not only does it have agricultural benefits, but composting also combats climate change. When plant wastes are sent to landfills they turn into carbon dioxide and methane, two of the most common greenhouse gasses. When those plants are composted, they lock up carbon from the atmosphere for decades! And when you compost and add that compost to your garden's soil, you are also sequestering additional carbon dioxide. Here's a brief look at how compost can help us in the one tonne challenge, courtesy of an excerpt from an article by the late Donella Meadows. THE GLOBAL CITIZEN: How Much Greenhouse Gas Does Your Garden Cut? Here, for you gardeners who want to quantify your own contribution to the climate -- and for policymakers who'd like to reward farmers for climate-stabilizing behavior -- is how he went about it [estimating compost's carbon credits]. "The biggest uncertainty relates to how deep the organic matter is going into the soil. I assume that the change in soil organic matter is confined to the top 8 inches. I suspect that you're actually leaching humus into deeper soil, which would affect the result a lot. So this is a conservative estimate." A silt-loam soil weighs roughly 85 pounds per cubic foot. Eight inches of it weighs 56 pounds per square foot. Organic matter is about 58 percent carbon. So soil with one percent organic matter contains (hmmm, one percent of 58 percent of 56 pounds) 0.3 pounds of carbon per square foot. Soil with 7.7 percent organic matter contains 2.5 pounds of carbon per square foot. David and Judy have increased the amount of carbon in every square foot of their garden by 2.2 pounds. It's a big garden, 0.4 acres. (Actually it's a communal garden, which David and Judy share with their neighbors.) That's 17,424 square feet. Multiply by 2.2 pounds of carbon per square foot -- let's see here -- that makes over 38,000 pounds of carbon removed from the atmosphere -- 19 tons! Jon writes to David: "You have sequestered 19 tons of carbon into your garden over the last 10 years. This is impressive! The average American releases 6 to 6.5 tons of carbon into the atmosphere each year. So you have offset about three years of an average American's emissions." For more info on reducing CO2 emissions, see our report "Fighting Global Warming at the Farmer's Market".
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