Composting not only reduces the waste stream and minimizes the production of greenhouse gasses, it produces nutrient-rich humus, a key ingredient to any sustainable agriculture, be it a single houseplant or next year's organic wheat crop. All organic matter will biodegrade with or without human intervention, but a little structure and oversight ensures it happens more efficiently. For example, in a landfill, yard waste breaks down largely by anaerobic decomposition, which produces potent greenhouse gasses like methane (CH4) and nitrous oxide (N2O) and can be a very slow process, with organic materials surviving undecomposed for decades. A properly engineered and well-maintained compost pile supports aerobic decomposition, with greatly reduced emissions of heat-trapping gasses, and produces a usable product more quickly.

 

The EPA estimates Americans produced over 250 million tons of garbage in 2007. Although 89 percent of that waste was recyclable — including compostable food waste — only 33 percent was actually recycled. A trip to the local waste transfer station, landfill, or even the alley dumpster will provide firsthand evidence of the EPA's findings. The rotten odors alone tell us the municipal solid waste stream (MSWS) is largely organic, with compostable yard trimmings and food scraps making up a quarter of the total (recyclable paper products make up the largest portion at 32.7 percent).

 

In practical application, exactly what can and cannot be composted depends on several factors. Composting is not a perfect science, but a few rules of thumb can be applied, whether you live in an apartment or on a farm. At home you can build a cold or a hot compost pile. Cold composting requires little maintenance and is best for leaves and grass clippings, which can be piled up and turned once a month. However, the heat produced may not be adequate to kill plants, so weeds should not be included. Also called slow composting, since it can take over a year to fully break down, cold composting works well when there is no immediate need for the compost. Hot composting is much quicker, producing usable humus in as little as four weeks but requires vigilant stewardship. Location, aeration, high carbon and nitrogen (or brown/green) content, sufficient depth, and moisture are key elements to a successful compost.

 

Again, composting is not a perfect science. Use the C/N ratios to help adjust your pile as needed. If the pile is well-aerated and properly moist but is not producing enough heat, add a high-nitrogen ingredient like horse manure. Conversely, if the pile smells like sulfur and is has a slimy texture (signs of too much nitrogen and anaerobic decomposition) add a high-carbon ingredient like sawdust. 

 

Finally, the last 20 years have seen enormous strides in municipal composting. Much of what can't be added to an apartment worm box, community garden or back yard compost pile, can be taken to a city run compost. Bulky yard items, grass clippings, even tree limbs are quickly turned into usable humus for neighborhood gardens and landscaping projects. The next frontier is cutting into the enormous quantity of biomass still going to landfills. Although the EPA, the USDA, and many city governments are making inroads in this area, the obstacles remain formidable. Much of the organic garbage going to landfills is what's called food residuals and includes last night's meatloaf and tuna casserole. Food residual pick up is an emerging part of municipal waste management, where separate containers are provided just for these items.

 

This article was reprinted with permission from SimpleSteps.org.