Composting is as simple as building a backyard pile of leaves, grass clippings and kitchen food scraps, tending it with water to add moisture as necessary and turning it over with a pitchfork once or twice a week to introduce oxygen and keep the microbial community thriving. At the other end of the spectrum, composting is a waste-management process that turns millions of tons a year of municipal, agricultural and industrial organic waste streams into high-value soil amendments utilized by homeowners, landscapers, golf course superintendents, park and athletic fields managers, vintners, vegetable growers, highway departments, green-roof installers, civil engineers and many others. In both cases and all points in between, composting is a biological process that depends on microbes, moisture and air to turn organic residuals into nutrient-rich, soil-building humus. Another critical element is the right mixture of “green” nitrogen-rich materials (e.g., food scraps, grass clippings) and “brown” carbon-rich materials (e.g., leaves, woody landscape debris). Because commercial composters rely on tipping fees — a per-ton cost paid by generators of organics residuals — to make the economics work, they utilize systems that keep the process moving along while not compromising the finished product. These include in-vessel, aerated static pile and windrow composting. In-vessel commercial composters are typically metal, concrete or fabric enclosures within which air, temperature and moisture levels can be monitored and controlled. Aerated static piles introduce air through piping or porous pads and do not require frequent turning. Windrowing involves placing the compost feedstock in long rows that must be turned frequently. The ideal internal temperature for an active compost pile is between 135° F and 160° F — hot enough to kill pathogens and weed seeds, but not so hot as to kill beneficial microbes. BioCycle, published since 1960, estimates that there are well over 4,000 composting facilities in the U.S. BioCycle’s online directory,, includes close to 1,000 facilities in the U.S. and Canada. Over BioCycle’s 52 years of publishing, an industry has emerged to service the private companies and government entities that run composting facilities. Challenges the industry faces include development of adequate and effective infrastructure to keep up with businesses’ and communities’ growing desires to divert organic residuals from the landfill and efficacy related to the emerging market for compostable products to replace traditional plastics used for foodservice, bags and packaging. Keeping organic waste streams out of the landfill, especially food waste from grocery stores, cafeterias, restaurants, food processors and households — and directing these materials to composting and anaerobic digestion — reduces emissions of methane from landfills. For a sample copy of BioCycle, a monthly magazine dedicated to advancing composting and compost use around the world, email Dan Sullivan is the Managing Editor of BioCycle.