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building compost

May 11, 2012

From Caleb

A lot of things go into the making of our food, but in reality it all comes down to matter reorganized by energy. The energy input for our food is powered by the sun. Most of our food begins in soil, which is a medium of support for plants, a source of vital nutrients, and a complex, synergetic ecology of organisms. It is possible to grow some food without soil in a hydroponic system, but a discussion of that will be saved for a later post after further research.

As per the NYC Department of Sanitation: “Compost is a nutrient-rich, dark, crumbly material that helps improve soil health and provides essential nutrients to plants. Compost results from the management of the natural decomposition process that turns the nutrients from once-living materials into humus, the rich, organic component of soil.” The Department of Sanitation actually has a really good explanation of the science of composting on their website. And science it is; ingredients and processes are critical to making a high-quality growth medium.

The Red Hook Community Farm in Red Hook, Brooklyn, is administered by Added Value. It is a 3.5 acre working farm with its own on-site composting operation. They are an interesting model for urban soil farming, because the farm is on a disused Parks Department playground. The entire site is covered with a layer of asphalt, and the soil sits atop this. This is a good thing. Red Hook is largely former industrial land, and the asphalt prevents the uptake of who knows what into the plants – certainly lead and other heavy metals, and a myriad of petroleum products. This development of soil on an impervious surface can be used on rooftops and even streets. The soil has been built to 18 inches in some beds over the eight years of the farm’s existence primarily via composting.

At the RHCF composting is undertaken by volunteers. “Windrows” are built about once a month, and the activity is referred to as the “big salad.” A windrow is built in layers, typically starting with a layer of wood chips, then alternating layers of “greens” and “browns,” with some active compost layered in to speed up the biological processes. Other ingredients are oxygen and water. The completed pile then begins to “cook.” Temperatures within the pile go to about 160 F. The temperature rise is due to the metabolic action of the organisms active within the pile.

Greens are comprised of kitchen scraps (no meat, dairy, significant amounts of oils). Greens come from a variety of sources. This is one of the places that the compost you save in your freezer all week until the Saturday farmer’s market ends up. They also get contributions from restaurants, the Park Slope Food Co-op, and other places. Also incorporated are weeds removed from the planting beds. Greens provide nitrogen for the process.

Browns are made up of leaf matter, which mostly comes from the lush ring of London plane trees that surround the garden, wood chips from the parks department, and sawdust from local woodshops. Other brown ingredients include things like biodegradable paper plates from a local business. Browns provide carbon which provides the fuel for the decomposition process.

There are a variety of industrial composting operations at a municipal level that use a lot of heavy equipment. But it is, at its core, a very simple (though rigorous) process that requires no equipment more complex than a shovel or perhaps a wheel barrow, resulting in a medium for growing food.

At the Red Hook Community Farm it is a lot of work, and all done by hand – they have no heavy equipment to aid in the process. It is not very glamorous either – handling a lot of half-rotted vegetables. It is curious to see what is discarded – an incredible amount of sound food. The most recent big salad had a lot of perfectly edible citrus, apples, onion, cauliflower, lettuce, carrots and other fruits and veggies. Americans are estimated to waste 40% of food grown, and in looking at the materials in the compost, it is not hard to imagine that this is true. A lot of the discarded material was not merely cores, peels, seeds, and ends, but whole foods that just spent too long in the fridge without being eaten.

Here are some other stats: food waste is by far the largest component of municipal solid waste in the US at 33.8%. Yard waste accounts for another 14.2%. In total this is 48% – basically half. It goes into landfills, where the material decomposes in an anaerobic process, resulting in the emission of methane gas. Some methane is captured, but most becomes a greenhouse gas 25 times more potent than carbon dioxide. By comparison, compost is an aerobic process, resulting in CO2 emission, and producing a useful product: soil.

One Comment leave one →
  1. Sara permalink
    May 12, 2012 12:24 am

    so much nice info in this article. questions: soil on top of asphalt? Does water leach through asphalt? What if anything leaches up from asphalt?

    And who has the secret knowledge to turn yard waste into the perfect brown material for compost? I heard a rumor that all the chipped wood from the wood debris after the Halloween snowstorm up here in the NE could not be used for compost. So many details about barriers to what seem like easy and natural solutions. I wish I knew the answer to the compost issue, but don’t have my finger on that pulse to find out. Maybe you do.

    I also enjoyed the chicken coop details.

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