Have you ever wondered about composting at home? This practical and convenient way to handle yard trimmings—leaves, grass, thatch, chipped brush, and plant cuttings—improves soil, protects the environment, and saves money. Homeowners were previously advised to mow often and let the clippings lay. But composting is now considered an excellent alternative. If you have a garden, a lawn, trees, shrubs, or even planter boxes, you have a use for compost.
What Is Composting?
Composting is the natural process of recycling organic matter, such as leaves and food scraps, into a valuable fertilizer that can enrich soil and plants. Anything that grows decomposes eventually; composting simply speeds up the process by providing an ideal environment for bacteria, fungi, and other decomposing organisms (such as worms, sowbugs, and nematodes) to do their work. The resulting decomposed matter, which often ends up looking like fertile garden soil, is called compost. Fondly referred to by farmers as “black gold,” compost is rich in nutrients and can be used for gardening, horticulture, and agriculture (Hu 2020).
How Does Composting Improve Soil Health?
Compost returns organic matter to the soil in a usable form. Organic matter in the soil improves plant growth by stimulating the development of beneficial microorganisms such as bacteria and fungi, loosening heavy clay soils to allow for better root penetration, improving the capacity to hold water and nutrients (particularly in sandy soils), and adding essential nutrients to any soil. Improving your soil is the first step toward improving plant health.
How Does Composting Help the Environment?
Yard trimmings and kitchen scraps represent more than 30% of what we throw away, using up valuable space in landfills (United States Environmental Protection Agency n.d.). Additionally, because of their high moisture content, grass clippings lower the efficiency of incineration systems. Composting can reduce the use of pesticides and chemical fertilizers in your yard. Healthy plants help clean the air, conserve soil, and beautify landscapes.
What Can I Compost?
Most yard trimmings will work as a mulch and for composting, but do not use diseased or infested plants as mulch without composting them first. Yard trimmings such as leaves, grass clippings, weeds, thatch, and the remains of garden plants make excellent compost. Other good additions to a compost pile include ground brush, wood ash, and kitchen scraps such as fruit and vegetable peelings, eggshells, and coffee grounds. Care must be taken when composting kitchen scraps. Unless you are a composting expert, do not compost meat, bones, or fatty foods such as cheese, salad dressing, and cooking oil. These foods ferment or putrefy, causing odors that attract rodents and other nocturnal animals that can be pests.
One concern with composting is the possible contamination of the compost with lawn care pesticides. Grass clippings and leaves treated with these products should not be used as a mulch immediately after application and mowing but can be used after they are composted. The most widely used pesticides degrade rapidly during composting or become strongly bound to organic matter in the compost. Their degradation is accelerated by the high temperatures and moist conditions that occur in a compost pile.
The Essentials of Composting
With the following principles in mind, everyone can make excellent use of organic wastes.
What happens in a compost pile? Bacteria, the most numerous and effective microbes, are the first to break down plant tissue. Fungi and protozoans soon join the bacteria. Often, a white layer forms just beneath the surface of the compost. This is usually due to fungi and actinomycetes, a class of filamentous bacteria. Springtails, mites, and other small insects, as well as earthworms, also play a role in decomposition once the compost has cooled.
Anything growing in your yard is potential food for the microbes in compost. Microorganisms use the carbon in leaves or woody wastes as an energy source. Nitrogen provides the microbes with the raw elements of proteins and nucleic acids to build their bodies.
Everything organic has a given ratio of carbon to nitrogen (C:N) in its tissues. A C:N ratio of 30:1 is ideal for the activity of compost microbes. This balance can be achieved by mixing. Table 1 provides target ratios for compost ingredients. Composts often are deficient in nitrogen when wood wastes are added to the mixture. This can be corrected by adding one pound of urea per cubic yard of compost mixture.
|Sawdust, wood, paper||400:1|
The more surface area the microorganisms must work on, the faster the materials decompose. Chopping garden wastes with a shovel or machete, or running them through a shredding machine or lawn mower, speeds composting.
A large compost pile insulates itself and holds the heat of microbial activity. Its center will be warmer than its edges. Piles smaller than three feet cubed (27 cu. ft.; 3–4 ft. tall) have trouble holding this heat in the winter, while piles larger than five feet cubed (125 cu. ft.; 5–6 ft. tall) do not allow enough air to reach the microbes at the center. These proportions are important if your goal is fast, high-temperature composting. Large piles are useful for composting diseased plants or trees, as the high temperatures will kill pathogens and insects.
Moisture and Aeration
All life on Earth, including compost microbes, needs a certain amount of water and air to survive. Microbes function best when a compost heap has many air passages and is about as moist as a wrung-out sponge. Generally, the moisture content of compost should be 50 to 60% on a total-weight basis. Extremes of sun or rain can adversely affect this moisture balance. Wet piles that leach water become deficient in oxygen and fermenting, and cause odor problems. Never cover compost piles with plastic, as this does not permit introduction of air. Cured composts can be covered, but this can also cause problems. Compost blankets allow for air exchange but shed rainwater from piles.
The larger the pile and the higher the temperature, the faster the composting proceeds—up to a certain point. At temperatures higher than 160 degrees Fahrenheit, composting slows down and charring or burning begins. This becomes a problem in dry composts, particularly in the summer.
How to Prepare and Use Compost
Remove grass and sod cover from the area where your compost pile will be constructed, to allow for direct contact of the materials with soil microorganisms. The following compost heap "recipe" is recommended for best results:
1st layer: 3–4" of chopped brush or other coarse material. This material allows air circulation around the base of the heap.
2nd layer: 6–8" of mixed scraps, leaves, and grass clippings. Materials should be "sponge damp."
3rd layer: 1" of soil, which serves as an inoculant by adding microorganisms to the heap.
4th layer: (optional) 2–3" of manure, which provides the nitrogen needed by microorganisms. Sprinkle lime, wood ash, and/or rock phosphate over the layer of manure to reduce the heap's acidity. Add water if the manure is dry. If organic sources of nitrogen are not available, add one pound of urea fertilizer or 10 pounds of composted poultry manure per yard of leaves or ground brush. Soak these high-carbon materials with water before composting. Manure generally should not be used in urban areas to reduce the potential for fly problems.
5th layer: Repeat steps 1–4 until the bin is full. Scoop out a "basin" at the top to catch rainwater under summer conditions.
A properly constructed compost heap will reach temperatures of about 140 °F in four to five days. At this time, "settling" can be observed, which is a good sign that the heap is working properly.
After three to four weeks, fork the materials into a new pile, turning the outside of the old heap into the center of the new pile. Add water if necessary. Then, turn your compost a second or third time. The compost should be ready to use within three to four months. A heap started in late spring can be ready for use in the autumn. Start another heap in autumn for use in the spring. Compost can be generated even faster by turning the pile more often. Check the internal temperature regularly; when it decreases substantially (usually after about a week), turn the pile.
Compost is ready to use when it is dark brown, crumbly, and earthy-smelling. Let it stabilize for a few extra days and screen it through a 1/2" screen if the finest product for germination of seedlings is desired. Compost generally should be at least four to six-months-old before using with plant seedlings. Apply a 1–2" layer of compost and work it in well where you want to grow root crops. Leave it on the surface or work it 1–2” into the surface of the soil for most applications. It is best to keep organic matter near the soil surface. This is known as mulch gardening. It is much easier to control weeds in gardens mulched with compost between rows of plants.
Compost used in these circumstances does not have to be as decomposed as compost that is worked into seed beds. For that purpose, have the soil tested for pH and major nutrients (N, P, and K) every two to four years and adjust the amount of lime, ash, fertilizers, etc., on the basis of feedback from your county extension educator or county master gardener. Table 2 is a guide to more efficient composting.
|The compost has a bad odor.||Not enough air.||Turn it. Add dry material if the pile is too wet.|
|The center of the pile is dry.||Not enough water.||Moisten and turn the pile.|
|The compost is damp and warm only in the middle.||Too small.||Collect more material and mix the old ingredients into a new pile. Turn the pile.|
|The heap is damp and sweet-smelling but will not heat up.||Lack of nitrogen.||Mix in a nitrogen source like fresh grass clippings, manure, composted poultry manure, bloodmeal, or urea fertilizer.|
Compost Bins That Can Be Used at Home
Snow Fence Bin
Bins made with pre-fabricated snow fencing are simple to make and easy to move and store. To build this bin, buy the appropriate length of pre-fabricated fencing, and fasten two-by-fours as corner posts to the bottom to form a circle.
Woven Wire Bin
One easy-to-make, economical container requires only a length of woven wire fencing. Multiply the diameter you want for the compost heap by 3.2 for the length of fencing to purchase. Fasten the ends with wire or three or four small chain snaps (available at hardware stores) to make a circle.
Compost bins can be made with cement blocks or rocks. Just lay the blocks without mortar, leaving spaces between each block to permit aeration. Pile them up to form three sides of a square container or a three-bin unit. This type of bin is sturdy, durable, and easily accessible. Keep the bin at least 3 inches away from the walls of houses to prevent deterioration of siding.
Wooden Pallet Bin
Covered bins allow convenient protection from pests and heavy rains. Construct bins with removable fronts or sides so that compost materials can be easily turned. Old wooden pallets can be used for construction. Wire mesh can be substituted for wooden sides to increase air flow.
Turning bins are a series of three or more bins that allow compost to be made in a short time by turning the materials on a regular schedule. They are most appropriate for gardeners with a large volume of yard trimmings and the desire to create high-quality compost. Compost can also be turned with only one bin by removing the bin from around the heap, setting up the empty bin nearby, and forking the material into the now-empty bin.
Rotating drum bins, which turn using a hand crank, are also commercially available. If your own kitchen, yard, and garden do not generate enough material to fill your bin, ask your neighbors for their clippings and leaves, or start a neighborhood composting project.
Yard trimmings can easily be composted in open heaps. Bins are not required. When food wastes are added, however, the compost may have to be confined in bins that keep out animals such as raccoons, skunks, etc. City ordinances against backyard composting were passed in many areas of the United States decades ago to control pests and flies, so check area regulations.
Food wastes and manures can easily cause fly problems unless great care is taken to cover them with a foot-thick layer of cured compost,
Prefabricated plastic compost bins can be purchased at hardware and gardening stores, as well as online and in catalogs. These are sometimes available locally at below-market cost.
Woody yard trimmings, leaves, and grass clippings can be used as mulch for weed control and water retention by simply spreading them beneath plants. For woody materials up to 1" in diameter, rent or purchase a chipper/shredder, or cut the material with hand tools. Tree services often deliver free wood chips. Chips can also be used for informal garden paths. Make sure that the chipped wood has been stored in a heap tall enough to reach temperatures of 110–160 °F so that pathogens and pests are killed by the heat. The addition of one pound of urea, or 10 pounds of composted poultry manure per cubic yard of shredded wood, with lots of water, speeds up the process.
The “Don't Bag It” Lawn Maintenance Plan
This nationwide program was developed in Texas and saves homeowners time, energy, and the cost of fertilizers and pesticides. It also reduces the amount of waste going into landfills. The principle is simple—leave clippings on the lawn, where they can work their way back into soil, improving soil health while reducing pesticide and fertilizer use.
Grass clippings contain valuable nutrients that can generate up to 25% of a lawn's total fertilizer needs. One hundred pounds of grass clippings can generate and return to the lawn as much as three to four pounds of nitrogen, one-half to one pound of phosphorus, and two to three pounds of potassium. These are the three most important nutrients that lawns require, and are commonly supplied in lawn fertilizers. Additionally, grass clippings are 75–85% water and decompose readily, so they do not contribute to thatch (an unhealthy, organic debris-layer between the soil and live grass). Finally, average mowing time can be reduced by up to 30% when the clippings are not bagged, saving time and fuel.
Hu, Sheila. 2020. “Composting 101.” What is Composting? Natural Resources Defense Council. https://www.nrdc.org/stories/composting-101.
United States Environmental Protection Agency. n.d. “Composting at Home.” Accessed September 24, 2021. https://www.epa.gov/recycle/composting-home.