Compost is a valuable organic soil amendment, and is the finished material of decomposed plant matter and food scraps. Compost is dark in color, earthy in smell, and crumbly in texture. Compost resembles soil, but it is very different in its makeup. Soil is mostly rock and mineral, while compost is entirely organic matter. In a garden or on a farm, compost is not used in place of soil but is added to soil to improve soil health. Healthy soil is biologically active and rich in organic matter, and compost feeds the soil ecosystem. Inspiring gardeners and farmers to make and use compost in order to improve and amend their soil.
Using compost:
Additional resources on using compost:
Converting a lawn to a garden using sheet mulching
Using compost and other carbon farming practices
Composting is the process of making compost. Composters control the decomposition of dead plants and food scraps using a composting method. Decomposition occurs by building an environment that encourages microorganisms to thrive and produce compost. This environment can vary based on the method used, and usually is built in a large pile or row, a composting bin, or a series of bins or bunkers.
Fungi, bacteria, and invertebrates are the microorganisms responsible for composting.Fungi can be seen as white, string-like mycelium strands stretching across woody, carbon-rich materials in your compost pile. Bacteria is largely invisible, but is the most active and powerful decomposer, capable of raising the temperature of your pile to create “hot compost” environments that rapidly decompose materials. Invertebrates are the visible bugs that act as shredders, rippers, and movers of the bulkier material in your pile, and are typically the most active in “cold compost” piles. Fungi, bacteria, and invertebrates consume the “big four” to produce compost.
The Big Four are the ingredients (or feedstocks) added to a compost pile to encourage microorganisms to decompose your green waste and food scraps and create compost. The Big Four include:
The composting process begins when conditions are right and the Big Four are present in a compost pile. As microorganisms decompose the browns and greens, conditions in the pile will change. The volume of the pile will decrease, oxygen will be consumed, and water will drain and evaporate from the pile. This will impact the rate of decomposition, requiring composters to check and correct these conditions as needed. The most iconic change in a compost pile is the fluctuation of temperature. Under the best conditions, compost piles will reach temperatures of 150 degrees Fahrenheit. This heat is generated internally from the activity of bacteria decomposers, and so the temperature of a compost pile is often used to determine how quickly materials are decomposing. Compost piles that reach “hot” temperatures may produce finished compost in 3-6 months, while “cold” compost piles might take a year or longer to produce the same amount.
Additional resources on how to compost:
What you can compost in your backyard bin
Troubleshooting your compost pile
Frequently asked questions about composting
Finished compost is dark, light and crumbly, and sweetly earthy smelling. Finished compost has no resemblance of the original materials or feedstocks in the pile, with the exception of some remaining woody material. Depending on the composting method, you might harvest finished compost from the bottom of an active pile, or wait until the entire pile resembles finished compost. This harvested compost is sometimes put through a ½ inch screen to separate any unfinished decomposed materials, which are added back to the compost pile. This screened compost is then set aside for a period of time in order to “cure” itself before being adding to soil. Curing compost for at least 2 weeks allows remaining decomposers to slow down, stabilize, and disperse. Uncured compost can “shock” existing and new plants because of its extremely high biological activity compared to the soil it’s applied to.
Additional resources:
Tools For Building Healthy Soil
Backyard Composting Webinar Recording
While composting prevents food waste from entering the landfill, it is not an excuse to waste food! The highest and best use of edible food is to eat it, making food waste prevention an important strategy ahead of composting. Composting closes the loop in the food cycle and returns some of the nutrients and fertility to the soil. However, it cannot return the other resources used to produce, process, and distribute food from the farm to your plate. Resources for reducing food waste are found at www.StopFoodWaste.org.
Composting is also a powerful action that reduces global climate change. Preventing food waste and plant matter from entering the landfill prevents a powerful greenhouse gas called methane from being generated. Applying compost to soil also stimulates plant growth and feeds soil organisms that in turn removes carbon dioxide from the atmosphere and sequesters carbon in the soil. Using compost to sequester carbon in the soil is referred to as a Carbon Farming practice. Learn more about carbon farming at www.StopWaste.org.