Composting

Yard trimmings and food residuals together constitute 23 percent of the U.S. municipal solid waste stream. That's a lot of waste to send to landfills when it could become useful and environmentally beneficial compost instead!

Compost is organic material that can be used as a soil amendment or as a medium to grow plants. Mature compost is a stable material with content called humus that is dark brown or black and has a soil-like, earthy smell. It is created by: combining organic wastes (e.g., yard trimmings, food wastes, manures) in proper ratios into piles, rows, or vessels; adding bulking agents (e.g., wood chips) as necessary to accelerate the breakdown of organic materials; and allowing the finished material to fully stabilize and mature through a curing process. Mature compost, however, includes the production of high temperatures to destroy pathogens and weed seeds that natural decomposition does not destroy.

Technology

Technology iconThe decomposition of organic materials in composting involves both physical and chemical processes. During decomposition, organic materials are broken down through the activities and appetites of various invertebrates that will naturally appear in compost, such as mites, millipedes, beetles, sowbugs, earwigs, earthworms, slugs, and snails. These microorganisms need adequate moisture and oxygen to degrade the organic materials in the most efficient manner.

Microbes in the pile create considerable heat and essentially "cook" the compost. Temperatures between 90 and 140 degrees Fahrenheit are common in properly maintained compost piles, but may not reach these levels in backyard compost piles. These high temperatures are necessary for rapid composting as well as for destroying weed seeds, insect larvae, and potentially harmful bacteria. When the compost is finished, it has a crumbly texture throughout the pile.

Backyard or Onsite Composting
Small scale in nature, Backyard composting generally uses bins or piles of organic matter

Vermicomposting
This composting process uses worms to process organic material and produce a nutrient-rich soil amendment.

Aerated (Turned) Windrow Composting
This composting process turns organic matter regularly in order to provide the needed oxygen.

Aerated Static Pile Composting
This composting process mixes organic matter together in one large pile instead of rows. To aerate the pile, layers of loosely piled bulking agents (e.g., wood chips, shredded newspaper) are added so that air can pass from the bottom to the top of the pile. Tubing might also be used.

In-vessel Composting
This composting process uses an air-tight container such as a drum, silo, or concrete-lined trench to control temperature, moisture, and aeration.

Quick Web Links
What to put in the mix

Environmental Benefits

Environmental Benefits iconCompost enriches soils
Compost has the ability to help regenerate poor soils. The composting process encourages the production of beneficial micro-organisms (mainly bacteria and fungi) which in turn break down organic matter to create humus. Humus--a rich nutrient-filled material--increases the nutrient content in soils and helps soils retain moisture. Compost has also been shown to suppress plant diseases and pests, reduce or eliminate the need for chemical fertilizers, and promote higher yields of agricultural crops.

Compost helps cleanup (remediate) contaminated soil
The composting process has been shown to absorb odors and treat semivolatile and volatile organic compounds (VOCs), including heating fuels, polyaromatic hydrocarbons (PAHs), and explosives. It has also been shown to bind heavy metals and prevent them from migrating to water resources or being absorbed by plants. The compost process degrades and, in some cases, completely eliminates wood preservatives, pesticides, and both chlorinated and nonchlorinated hydrocarbons in contaminated soils.

Compost helps prevent pollution
Composting organic materials that have been diverted from landfills ultimately avoids the production of methane and leachate formulation in the landfills. Compost has the ability to prevent pollutants in stormwater runoff from reaching surface water resources. Compost has also been shown to prevent erosion and silting on embankments parallel to creeks, lakes, and rivers, and prevents erosion and turf loss on roadsides, hillsides, playing fields, and golf courses.

Links

Links iconThe Environmental Protection Agency's Composting website provides information on how to develop your own composting system.
Website: http://www.epa.gov/epawaste/conserve/rrr/composting/index.htm

BioCycle Journal of Composting & Organics Recycling is America's foremost magazine on composting and organics recycling. BioCycle shows you how to turn organic residuals (e.g., woody materials, yard trimmings, food residuals, biosolids, manure) into value-added products.
Website: http://www.jgpress.com/biocycle.htm

California's Organic Materials Management page provides information on compost, mulch, grasscycling, and other topics relating to the management and use of organic resources.
Website: http://www.calrecycle.ca.gov/Organics/Default.htm

The Cornell Waste Management Institute provides good information on the fundamentals of developing a composting program including the science and engineering.
Website: http://cwmi.css.cornell.edu/composting.htm

The US Composting Council (USCC) is dedicated to the development, expansion, and promotion of the composting industry based upon science, principles of sustainability, and economic viability.
Website: http://www.compostingcouncil.org/