Composting PDF

ID-192 Composting By Craig G. Cogger, Extension soil scientist, Washington State University; Dan M. Sullivan, Extension soil scientist, Oregon State University; and James A. Kropf, Extension agent, Pierce and King counties, Washington State University. Adapted for Kentucky by Brad Lee, Extension sp...

ID-192 Composting By Craig G. Cogger, Extension soil scientist, Washington State University; Dan M. Sullivan, Extension soil scientist, Oregon State University; and James A. Kropf, Extension agent, Pierce and King counties, Washington State University. Adapted for Kentucky by Brad Lee, Extension specialist for water quality, and Richard Durham, consumer horticulture Extension specialist and state Master Gardener coordinator, University of Kentucky. Science of Composting In this chapter: Composting carries out part of the earth’s biological cycle Science of Composting 01 of growth and decay. Plants grow by capturing energy from the sun, carbon dioxide Managing the Decay Process 02 from the air, and nutrients and water from the soil. When plants How to Make Compost 03 (and the animals that eat them) die, they become raw material for Using Compost 04 the composting process. Microorganisms, fungi, insects, worms, mites, and other creatures convert the carbon from dead plants Worm Bins: A Way to Compost Food Wastes to Avoid Pests 04 into energy for their own growth, releasing carbon dioxide into Commonly Asked Questions About Worms 05 the air and generating heat in the process (Figure 13.1). They also recycle nutrients from decaying plants into their own bodies and Health and Safety Questions 05 eventually back into the soil through their waste or as decayed Troubleshooting Tips 06 products as they die. Other plants and microorganisms use the For More Information 06 carbon and nutrients released by the composting process, and the cycle begins again. The material that remains from the decay process is similar to G ardeners have long made and used compost to improve soil organic matter. It holds water and nutrients in the soil and garden soil. makes the soil more porous and easier to dig. Today, we also compost plant and vegetable matter The decay process can be manipulated to make it proceed because it is an important way to reduce the waste burned or quickly. The key is to balance food, water, and air in the com- dumped in landfills. Yard wastes and vegetable scraps can make post pile to favor the growth of thermophilic (heat-loving) up as much as 20 percent of household garbage. Composting microorganisms. effectively recycles that waste into valuable organic matter that One byproduct of microbial activity is heat. When condi- can be used as soil amendments. tions are favorable for high-temperature microorganisms, Backyard composting is a simple, yet important, way to compost piles heat rapidly to 120°F to 150°F. The high tem- improve our communities and the environment. perature kills most weed seeds and pathogens (disease organ- The benefits are the same whether you compost in carefully isms) but does not kill mycorrhizae (beneficial fungi that help Rawor tended hot piles materials in passively managed slow piles. plant roots absorb nutrients). Once the hot phase is complete, Raw materials Heat CO2 Organic matter Water (including Heat Organic Raw materials mattercarbon, chemical Water CO2 energy, protein,chemical (including carbon, nitrogen) energy, protein, nitrogen) Water Heat CO2 Organic Minerals matter (including carbon, chemical (including nitrogen and Minerals energy, protein, nitrogen) Finished compost other nutrients) (including nitrogen and Finished compost other nutrients) Organic matter MineralsWater (including nitrogen and Compost pile (including Organic mattercarbon, chemical Water Finished compost energy,carbon, nitrogen, protein, humus), other nutrients) Microorganisms Compost pile (including chemical minerals, water, microorganisms energy, nitrogen, protein, humus), Microorganisms Organic matter Water minerals, water, microorganisms Compost pile (including carbon, chemical energy, nitrogen, protein, humus), Microorganisms minerals, water, microorganisms O2 O2 Figure 13.1. The composting process. The amounts of carbon, chemical energy, protein, and water in the finished compost are less than in the raw materials, and the finished compost has more humus. The volume of the finished compost is 50 percent or less of the volume of raw material. O2 CHAPTER 13 Composting lower-temperature microorganisms, worms, insects, and other manure mixed with bedding, spoiled alfalfa hay, and deciduous invertebrates complete the decay process. leaves. These materials are handy for ensuring the success of If ideal conditions for hot composting are not maintained, hot compost piles. microorganisms still break down wastes, though decay is slower, If balanced raw materials are not available, mixing bulking cooler, and less effective at killing weed seeds and pathogens. agents with energy sources provides the right balance of mois- Compost produced this way is still useful as a soil amendment, ture, air, and nutrients for rapid composting. A mixture of one but it may contain weed seeds or pathogens if they were in the part energy source with two parts bulking agent (by volume) components used to make this “cold” compost. usually gives a reasonable mix for rapid composting. If energy materials are not available, a high-nitrogen fertilizer such as urea (44–0–0) or a high-nitrogen lawn-type fertilizer (without Managing the Decay Process pesticides) may be added at a rate of about four ounces (one-half The speed of the composting process and the quality of the cup) per bushel, or about two to three pounds per cubic yard finished compost are influenced by food, particle size, mixing, of starting compost material. pile size, moisture, aeration, microorganisms, and nutrients. Particle Size Food (Raw Materials) Small particles have more surface area for microbial activity For fast composting, the initial mix must have the proper and are easier to mix. Grinding, cutting, smashing, or chopping moisture and air content as well as organic materials that pro- raw materials reduces particle size. Hot composting requires vide a rich food (energy) source for bacteria. Table 13.1 shows a relatively uniform particle that is one-eighth to one-half inch some materials commonly used in making compost. They are in diameter. separated into energy materials, bulking agents, and balanced Often, woody branches that have not been ground make materials. it difficult to turn a pile. They also decompose very slowly. Energy materials provide the nitrogen and high-energy car- Grinding or chipping woody branches or piling them sepa- bon compounds needed for fast microbial growth. If compost rately to allow them to slowly decay on their own may make lacks bulking agents, these materials usually are too wet and the composting process work more efficiently. dense to allow much air into the compost pile. When the pile is opened, it will have a foul, “rotten egg” smell. Mixing Bulking agents are dry, porous materials that help aerate Contrary to popular opinion, layering is not the best way to the compost pile. They are too low in moisture and nutrients build a pile. If all the materials are on hand when the pile is being to decay quickly on their own. built, mix them thoroughly throughout the pile. If materials Balanced raw materials have both energy and bulking accumulate over time, add new materials to the center of the agent properties. These materials compost readily without pile. This practice helps aerate the center, where lack of oxygen being blended with other ingredients. Examples include horse is likely to occur. Table 13.1. Compost raw materials. Pile Size Energy materials (High moisture, low porosity, high nitrogen) If you are hot composting, the pile must be big enough to Grass clippings hold heat. A pile of about one cubic yard is big enough for Fresh dairy, chicken, or rabbit manure year-round composting, even in cold-winter areas. A hot pile Fruit and vegetable waste decays much faster than a cold pile. Small piles are usually Garden trimmings colder because they have small cores that hold less heat. They Bulking agents (Low moisture, high porosity, low nitrogen) also dry out faster. Wood chips Sawdust Grass hay Moisture Wheat straw All materials in the pile must be moist but not soaking wet. Corn stalks Check moisture when the pile is turned. The mixed material Plain cardboard (not coated in slick paper or plastic) should feel moist, but you should not be able to squeeze water Balanced raw materials out of it. At dry times of the year, you may need to add water. (Low to medium moisture, medium porosity, medium nitrogen) Ground-up tree and shrub trimmings Horse manure and bedding Air Deciduous leaves Legume hay The microorganisms responsible for fast decomposition Cow/dairy manure with bedding need oxygen, so the pile needs to be porous enough to pull in 13-2  Composting CHAPTER 13 outside air to replenish oxygen as it is used. Including bulking Slow (Cold) Composting agents in the mix creates a porous pile. As the pile decomposes, it will settle, reducing its exposure to air (aeration). Turning the You can turn yard wastes into a useful soil amendment pile or adding more bulking agents improves aeration. conveniently and easily by slow composting. It often is the best method for people who do not have the time to tend a hot compost pile. Simply mix nonwoody yard wastes into a Microorganisms pile and let them sit for a year or so. Microorganisms, insects, Raw materials used to form a compost pile usually contain earthworms, and other decomposers will slowly break down all the microorganisms needed to make compost. If they’re the wastes. A mixture of energy materials and bulking agents needed, the best source of microorganisms is finished compost. provides the best food source and environment for decomposi- You don’t need compost starters with special microorganisms. tion (see Table 13.1). For a new compost pile, a few cups of garden soil may help start Add fresh wastes by opening the pile, placing the wastes in the process. the center, and covering them. This method helps aerate the pile and also buries the fresh wastes so they do not attract pests Nutrients such as flies, rats, and raccoons. Fruit and vegetable wastes are particularly appealing to pests, Just like people, microorganisms need nutrients (such as so be sure to bury these wastes within the pile. If pests are still a nitrogen, phosphorus, and sulfur) to grow and reproduce. These problem, you may need to screen the pile or use another method nutrients occur in the raw materials used in the compost mix. of composting those wastes. You usually don’t need additional fertilizer from any source One option is to bury them directly in your garden. Dig a (organic or inorganic). hole or trench about a foot deep, add a few inches of waste, mix Nitrogen fertilizer may be beneficial for mixes consisting it with the soil, and refill the trench with soil. mainly of bulking agents. The best way to add fertilizer is to Another way to avoid pests is to compost fruit and vegetable dissolve it in water and wet the pile with a dilute solution. wastes in a worm bin (described later in this chapter). Additives such as blood meal and bone meal are simply Slow composting does not produce the heat needed to kill organic fertilizers; they do not contribute anything magical to many weed seeds. It is best to pull and compost weeds before the compost pile. they go to seed. If you put seeds in the compost pile, be prepared for more weeding. How to Make Compost You don’t need a bin or other container to make compost. Fast (Hot) Composting Piles work well. Some people prefer containers, however, If you create and maintain a balance of air, moisture, and because they look neater or because it is easier to shield them energy for compost microorganisms, they produce a hot pile from pests. Containers can be simple or fancy. Make them from that breaks down quickly. The heat kills many weed seeds and materials such as old pallets, lumber, mesh fencing, or cinder disease organisms. Making hot compost takes extra effort, but blocks (Figure 13.2). it produces a high-quality product quickly. One method for making hot compost is described below. Steps for building the pile 1. Collect enough material to make a pile at least one cubic yard in volume. (An open pile five feet wide at the base by three feet high holds about a cubic yard.) Use roughly two parts bulking agent to one part energy material (see Table 13.1). Chop, shred, mow, or smash coarse materials so they will break down faster. 2. Start the pile by adding energy material and bulking agent, then mix with a pitchfork. 3. Squeeze a handful of the mixed material to check its mois- ture level. If you can barely squeeze out a drop of water, the moisture level is ideal. If the pile is too dry, add water and check the moisture again. If it is too wet, mix in some drier material. 4. Continue adding energy material and bulking agent, mixing, and checking moisture until the pile is built. Figure 13.2. Some people compost in open piles; others prefer using bins. 13-3 CHAPTER 13 Composting Turning Mulching Use a pitchfork to turn the pile weekly, and add water when Compost applied to the soil surface helps to control weeds, needed. Turning improves the porosity of the pile and speeds conserve water, and protect soil from erosion. The best time decay. It also mixes material from the outside of the pile into to apply compost mulches is in early summer, after plants are the hot center. Cover the pile during rainy periods so it will established and the soil has warmed. Later, the mulch can be not get too wet. dug or tilled into the soil. When you are mulching perennial Curing plantings, choose compost made from woody bulking agents; it decomposes slowly, resists compaction, and slows the estab- After initial mixing, a regularly turned pile usually stays hot lishment of weeds. (120°F to 150°F) for several weeks to a month. It will shrink to Sometimes compost will form a mat, crusting on the soil about half its original volume by the end of this time. surface and impeding water movement into the soil. If matting The pile then needs to sit another four to eight weeks to cure. does occur, simply work the compost into the upper soil layers Curing affects the availability of nitrogen and the microbial to prevent crusting. activity of the compost. Uncured compost may harm some plants, especially when compost is used in potting soil or to start seeds. Curing is less critical when small amounts of compost are Worm Bins: A Way to Compost worked into soil. With two compost piles, one batch can cure while another batch is started in the second pile. Food Wastes to Avoid Pests Temperatures during curing are 80°F to 110°F. The compost Kitchen scraps composted in an outdoor bin sometimes is ready to use when at least eight weeks have passed since initial attract pests, so you might prefer to compost them using mixing, the pile no longer heats when turned, and the material worm bins. looks dark and crumbly. Starting a Worm Bin What if Hot Compost Isn’t Hot? Most worm bins are made of plywood, but large plastic If the pile isn’t hot, do the following: tubs with covers also work, as long as it is possible to drain off If the pile is dry, add more moisture. excess moisture. One solution is to nest two plastic contain- If the pile is mostly bulking agent, add energy materials or ers and make holes in the bottom and and the lower third of nitrogen fertilizer. the sides of the upper container, allowing excess moisture to If the pile is too wet, add more bulking agent. In the rainy escape and collect in the lower container. Worms avoid light, season, cover the pile or build a larger one. so the container ‘s interior should be dark, and it should have a If the pile has a foul smell, try turning it more often or adding good lid. The lid should cover the top but does not need to be more bulking agent to increase the amount of air. securely attached. The container should have air holes—either If the pile is too small, try building a larger pile to better hold on the lid, sides, or, if the container is not sitting directly on the heat. ground, on the bottom. If you use a plastic bin, be sure to add Sometimes you may have several problems to overcome. If both drainage and air holes. Never use a container that has been the pile will not heat, all is not lost, because the pile will eventu- used for storing toxic chemicals. Construction plans for worm ally break down by the slow method. bins are available from many Extension offices or county solid waste departments. The size depends on how much food waste you add per week. Using Compost A box measuring one foot by two feet by three feet can handle Compost’s biggest benefit is to the garden. Mix compost with six pounds of kitchen waste per week, which is about average soil to add organic matter or use it as mulch. for a family of four to six. Place worm bins where you can control temperature and moisture. An ideal temperature range for worms is from 55°F Amending Soil to 77°F. Worms also need a moist environment (more on this Well-decomposed, earthy compost is a good soil amend- below), and air circulation is a must in and around a worm box. ment. It makes soil easier to work and creates a better medium Choose a location that is convenient for maintaining the box. for plant growth. Mix one to two inches of compost into your Start by putting bedding in the worm box. Corrugated card- soil before you plant a vegetable garden, lawn, flower bed, or board, newsprint, and newspaper shredded in one-inch-wide cover crop. strips make excellent bedding. Worms need some grit for break- ing down their food, so add a little topsoil for this purpose. Put the worms in the bedding with their first feeding of food waste. Many food wastes can be composted in worm bins. These wastes include fruit and vegetable peels, grains, pasta, baked 13-4  Composting CHAPTER 13 Commonly Asked Does a worm have teeth? Worms have no teeth for chewing their food. Do worms need air? Worms need a constant supply of oxygen Questions About Worms They grind food in their gizzard by muscle from the air. The oxygen diffuses across the action. moist tissue of their skin, from the region of greater oxygen concentration (air) to that of Can a worm see? How does a worm grind his food? lower concentration (inside the worm). No, worms don’t have eyes. However, they A worm can take only a small particle of soft, are very sensitive to light, and they try to moistened food in its mouth. It ingests the How do I use worm compost? hide as soon as they are exposed to light. food along with a grinding material such Use worm compost like any other compost. as sand, topsoil, or limestone. Contractions Sterilizing is not necessary. Where is the worm’s mouth? from muscles in the gizzard compress the The worm’s mouth is in the first anterior particles against each other, thus mixing segment. There is a small protruding lip just them with fluid and grinding them into over the mouth. When the worm is foraging, smaller pieces. this lip stretches out to sense food. goods, coffee grounds, and ( in moderation) even coffee filters. the bedding is moist enough. If you can squeeze out five or Again, do not use animal products, including cheese, other more drops, the bedding is probably too wet. dairy products, or meat. Kinds of worms to use Moisture Two varieties of red worms adapt to a box environment: In order to survive, worms require 75 to 90 percent moisture Lumbricus rubellus and Eisenia foetida. These red worms feed in both their bodies and their bedding. To achieve this percent- on the surface of organic matter. age, add three pounds of water for each pound of dry bedding Nightcrawlers and other garden earthworms are very impor- (a ratio of 3:1). An easy way to check the moisture content of tant for soil improvement but won’t survive in a worm box. They bedding is to squeeze it. If you release a few drops of moisture, live only in furrows in the soil. Health and Safety Questions Cryptosporidium parvum. These pathogens are not taken up into plants, but they can Keep dog, cat, and pig manure out of your compost pile and garden. Some of be present in soil that adheres to roots or the parasites found in these manures may Are there any plant materials to keep out of low-growing leaves and fruits. The risk is survive a long time in compost or in the soil minimized if no fresh manure is used in the and remain infectious to people. a compost pile? garden. When composting by the slow method, Careful peeling or washing fruits and Are herbicides a problem in compost? keep diseased plants and seed heads of vegetables with detergent removes most On rare occasions, herbicides from weeds out of the compost pile. For any com- pathogens, but some risk remains. Thorough compost have harmed plants grown in soils post, avoid coarse, woody materials because cooking effectively kills pathogens. amended with the compost. they break down slowly and make the pile The greatest risk from manure-borne Herbicides break down in the environ- hard to turn. pathogens is for low-growing or under- ment over time. The rate of breakdown Some plants contain compounds that slow ground crops such as carrots, lettuce, and depends on the type of herbicide and envi- microbial decay. Eastern redcedar (Juniperus), strawberries. The edible part of these crops ronmental conditions. The high tempera- often used for fence posts because of its may become contaminated with soil, the tures and biological activity in a compost resistance to decay, can break down slowly in crops are difficult to wash, and they often pile accelerate herbicide breakdown. compost piles. Also, avoid black walnut leaves are eaten raw. Herbicides also are inactivated by binding and wood as these contain juglone, a com- Pathogens in fresh manure typically die with organic matter in compost. Breakdown pound that inhibits the growth of many plants. over time, especially when the manure dries and binding reduce the risk of herbicide Some extremely dense, woody materials, such out or is exposed to freezing and thawing. damage. as avocado pits, do not compost. The rate of die-off depends on the type of Lawn clippings can be a source of herbi- pathogen and manure and on environmen- cides in compost. The best way to eliminate Can a compost pile catch fire? tal conditions such as temperature, moisture, this source is to leave treated clippings on A compost pile will ignite only if it has a and sunlight. Thorough, high-temperature the lawn rather than composting them. very hot zone next to a dry zone. Fires do not composting kills pathogens, but it is difficult Other options are to reduce herbicide use in start in moist or small piles. to maintain these conditions in a backyard areas where you compost the residues, or to compost pile. If any manure is used in the use herbicides that break down quickly. Can I use manure in my compost? garden (even in compost), the gardener If you suspect there are herbicides in your should wait at least 120 days between compost pile, let the pile sit for a year or Fresh animal manures sometimes con- application to the garden and harvest. You tain organisms that can make people sick more, allowing more time for breakdown can limit your risk by excluding fresh manure and binding. (pathogens), such as the bacteria Salmonella from compost that will be used on fresh sp. and E. coli O157:H7, or the parasite garden crops. 13-5 CHAPTER 13 Composting Troubleshooting Tips For Worm Boxes: Provide adequate fresh bedding. If you see signs of rodents or other animals around the worm bin, place a sheet of wire Do not fill the bin with a lot of food waste mesh over the bottom of the bin or raise In General: until the worm population is established. the bin 12 to 18 inches off the ground. Control odors by removing excess or inap- Minimize fruit flies by covering fresh food Keep the lid latched or well secured if pos- propriate waste. waste completely with several inches of sums or raccoons are a problem. Make sure you haven’t added cheese or bedding and covering the bedding with a other animal products of any type to the sheet of newspaper, cardboard, or plastic compost system. tucked in around the edges. Number of Worms Worms can be obtained in many ways: Measure worms by weight rather than number. The number of worms you’ll need depends on the weight of the food waste Ask a friend who already maintains a worm bin. you plan to add each day, on average. Start by adding one pound Search the internet for worm sources. of waste each day for each pound of worms. Check with your county Extension office for any upcoming workshops involving composting with worms. After that, let the worms tell you how much food to add. If all the food is gone between feedings, add a little more. If the bin starts to smell because food is not being eaten, add less. Odor and Pest Control Adding Waste Control odors by not overloading the box with waste, using It is a good practice to vary where you bury wastes in the only appropriate waste, and providing adequate fresh bedding. worm box. You can bury kitchen wastes in about nine places in Do not fill the bin with a lot of food waste until the worm popu- a worm box that is two feet by two feet, and that’s nine feedings lation is established. Fruit flies are more of a nuisance than a before you have to bury again at the first location. serious problem, but the troubleshooting tips in this chapter Kitchen wastes break down very quickly, so you don’t need can help you deal with them. to grind them. Do pulverize egg shells. Leaving the Box Untended For More Information When you’re away from home for a few days, just feed the For more information, contact your county Extension agent. worms a little extra and leave them undisturbed. They can go three to four weeks without feeding. Make arrangements with University of Kentucky Cooperative Extension Service Publications someone else to feed the worms when you’ll be away longer. Home Composting (HO-75) Constructing a Wire-Mesh Compost Bin (ENRI-307) Changing the Bedding Constructing a Wooden-Pallet Compost Bin (ENRI-308) After some time, the bedding’s color will darken. Eventually, Constructing a Snow-Fence Compost Bin (ENRI-309) it will disappear as worms and microorganisms decompose Constructing a Wood-and-Wire Compost Bin (ENRI-310) it. Both processes create a less favorable environment for the Constructing a Garbage Can Compost Bin (ENRI-311) worms. Also, as castings accumulate in large amounts, it harms Constructing a Worm Composting Bin (ENRI-312) the worms—castings of one worm are toxic to other worms. Vermicomposting: Building a Worm Bin, University of Kentucky Decide when to change the bedding based on its condition and Extension Service the number of worms in the box. Population Control Worms multiply fast, so you’ll need to take care that they don’t overpopulate. Use extra worms to start a new worm box, or give them to someone else who is starting to worm compost. Revised 01-2024