Fundamentals of Composting

Globally, as much as one-third of the food grown for human consumption goes to waste on account of a variety of factors at every level from harvest, storage, transportation, and market (Gustavsson, 2015).  Not only is this a waste of the food itself, but also of the resources used and greenhouse gas emissions resulting in its production.  While food spoilage occurs in both the Global North and South, the majority occurs in the former, with nearly forty percent of food being wasted in the United States (Gunders, 2012).  Conventionally, food waste is put into landfills along with other types of organic matter including wood chips, grass clippings, brown leaves, paper wastes, etc.  Organic matter placed into landfills takes up a considerable amount of space in the fill, problematic as society nears “peak waste” (Hoornweg, 2013).  Upon entering the landfill, this relatively uncontaminated organic matter is mixed with other forms of waste, buried below ground, and compacted with heavy machinery.  The compaction process squeezes out most of the oxygen in the landfill, causing the organic matter to be decomposed under anaerobic conditions by methanogenic bacteria.  The methanogens produce methane, a greenhouse gas nearly twenty-five times more potent than carbon dioxide, as a by-product (USEPA, LMOP).  Fugitive methane escaping from landfills alone contributes to between three to twelve percent of greenhouse gas emissions in the United States, and accounting for twenty-four percent of total methane emissions in the US.  While some landfills are equipped with methane recovery systems or Landfill Gas-to-Energy (LFGTE) facilities, these commonly capture only a percentage of the escaping gas, as little as twenty percent, according to the IPCC (Intergovernmental Panel on Climate Change).  While having LFGTE systems are arguably preferable to having no gas recovery systems in existing landfills, their use should not be used as a justification for continuing the practice of putting organics in the landfill, as nearly any other method of handling organic wastes will result in reduced greenhouse gas production.  In an effort to increase short-term methane production, LFGTE operators will commonly create “wet cells” as opposed to “dry tombs” in landfills by soaking them with water.  This practice boosts gas yields, but results in an increases the total amount of fugitive methane emissions.  Lastly, landfill gas can be highly toxic as it is mixed with a variety of volatile pollutants in the landfill.  Regulating these toxic emissions is difficult as there are insufficient procedures for measuring non-point and diffuse emissions over a landfills surface (Sierra Club, 2010).  In conclusion, the process of landfilling organics thus described is highly degenerative, not only for taking up space in landfills and for producing gas emissions, but for ensuring the impossibility of composting the disposed organic matter into soil.  Unfortunately, the mindset of thinking of organic waste as fuel for LFGTE systems and then of recovered gas as a revenue stream is pervasive.  A high ranking city official explained to me at one time in a personal communication their philosophical opposition to composting and belief that organics “should go into the landfill, as they then turned into methane which then made the city money.”

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