Introduction to Composting

Composting is the decomposition of plant remains and other once-living materials to make an earthy, dark, crumbly substance that is excellent for adding to houseplants or enriching garden soil. It is the way to recycle your yard and kitchen wastes, and is a critical step in reducing the volume of garbage needlessly sent to landfills for disposal. It's easy to learn how to compost. Composting can even be done, cleanly and unobtrusively, indoors in apartment buildings and condominiums!
Composting is not a new idea. In the natural world, composting is what happens as leaves pile up on the forest floor and begin to decay. Eventually, the rotting leaves are returned to the soil, where living roots can finish the recycling process by reclaiming the nutrients from the decomposed leaves. Composting may be at the root of agriculture as well. Some scientists have speculated that as early peoples dumped food wastes in piles near their camps, the wastes rotted and were terrific habitat for the seeds of any food plants that sprouted there. Perhaps people began to recognize that dump heaps were good places for food crops to grow, and began to put seeds there intentionally.
Today, the use of composting to turn organic wastes into a valuable resource is expanding rapidly in the United States and in other countries, as landfill space becomes scarce and expensive, and as people become more aware of the impacts they have on the environment. In ten years, composting will probably be as commonplace as recycling aluminum cans is today, both in the backyard and on an industrial scale. Many states in the USA have stated goals or legislative mandates to drastically reduce the volume of waste being sent to landfills. Utilizing yard and kitchen wastes (which make up about 30% of the waste stream in the USA [1]) is a big part of the plan to minimize waste overall.
You can contribute to the 'composting revolution' by composting your own yard and kitchen wastes at home. If you have a large yard, you might prefer the ease of composting in a three-bin system out by the back fence. Apartment and condominium residents can get into the act with indoor 'vermicomposting' -- using earthworms to recycle kitchen wastes (offices can even recycle coffee grounds and tea bags with vermicomposting). Cities and towns can promote composting through home composting education efforts and the collection of yard wastes for large-scale composting. Whatever your style of composting, there's plenty of room to get involved!
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What to Compost
A great variety of things can be composted at home, saving them from a one-way trip to the landfill, and turning them into a valuable soil amendment for home use. This list describes some of the items you may want to add to your home compost pile. You may want to read about how to compost to learn about the difference between 'brown' and 'green' ingredients and the roles each plays in the composting process. Also, see the list of what NOT to compost
The following items can be added to your compost pile:
GRASS/LAWN CLIPPINGS
Actually, it's usually easier to leave grass clippings in the lawn, where they will decompose and benefit the soil directly. However, they can be composted, too. Be cautious to add grass clippings in very thin layers, or thoroughly mix them in with other compost ingredients, as they otherwise tend to become slimy and matted down, excluding air from the pile. Fresh grass clippings are high in nitrogen, making them a 'green' compost ingredient.
HAY
Farmers are often very happy to get rid of spoiled hay bales that have been out in the rain, and will give them away or sell them at a low price. Grass hay will probably contain a lot of seed, which can resprout in your garden. Alfalfa hay will compost very readily. The greener the hay, the more nitrogen it contains. Be sure that any hay you plan to compost is well-moistened prior to addition to the pile.
KITCHEN WASTES
Fruit and vegetable peels/rinds, tea bags, coffee grounds, eggshells, and similar materials are great stuff to compost. They tend to be high in nitrogen (this puts them in the 'greens' category), and are usually quite soft and moist. As such, kitchen wastes need to be mixed in with drier/bulkier materials to allow complete air penetration. Many people compost their kitchen wastes in enclosed worm bins or bury them 8" deep in the soil, to keep from attracting pests to an outdoor compost pile (check with your local government to see if it has regulations about this -- some forbid open piles containing food wastes because of the pest issue). Avoid composting meat scraps, fatty food wastes, milk products, and bones -- these materials are very attractive to pests.
LEAVES
If you live in an area where autumn leaves are still thrown away as garbage, cash in on the bounty each year by acquiring your neighbors' leaves! Generally, leaves are an excellent compost ingredient. They can mat down and exclude air, though, so be sure that any clumps are thoroughly broken up, or that the leaves are only used in very thin layers. Ash and poplar/cottonwood leaves can raise soil pH if used in compost -- this may not be beneficial if your soil is already alkaline, as many soils are in the West (especially in semiarid and arid climates). Dead, dry leaves are in the 'browns' category, while living green leaves contain abundant nitrogen and are considered 'greens'.
MANURE
Horse, cow, sheep, and poultry manures are often available for free from local ranches, farms, and stables. They can burn plants if applied when fresh, so be sure they get well composted. Manures typically contain quite a bit of nitrogen (the fresher the manure, the more nitrogen it contains) and are considered a 'green' ingredient. Some manures may contain weed seeds. Fresh manures can get a compost pile to heat up quickly, and will accelerate the decomposition of woody materials, autumn leaves, and other 'browns'.
STRAW
Dry straw is a good material for helping to keep a compost pile aerated, because it tends to create lots of passageways for air to get into the pile. Be sure to wet the straw, as it is very slow to decompose otherwise. Straw is definitely a 'brown' and also requires mixture with 'greens' to break down quickly. Many stables use straw as a bedding material for horses -- straw that has undergone this treatment is mixed in with horse manure and breaks down more quickly.
WEEDS AND OTHER GARDEN WASTES
Many types of weeds and old garden plants can be composted. Avoid weeds that have begun to go to seed, as seeds may survive all but the hottest compost piles. Some types of weeds are 'pernicious weeds' and will resprout in the compost pile -- avoid using these unless they are thoroughly dead. Green weeds are (you guessed it) a 'green', while dead brown weeds are a 'brown'.
WOOD CHIPS AND SAWDUST
Wood products belong in the 'browns' category, because they are fairly low in nitrogen. Some sawdusts, especially from broadleaved/deciduous tress, will break down quickly in an active compost pile. Others, especially from coniferous trees, will take longer to decay. Stir sawdust thoroughly into the pile or use very thin layers. Coarse wood chips will very slowly decay, and are probably better used as mulch unless you have lots of time to wait. Be sure not to compost chips or sawdust from any sort of chemically-treated wood -- you could be adding toxics like arsenic to your pile if you do.
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What NOT to Compost
Whether because of toxins, plant or human diseases, or weed troubles, there are some things that shouldn't be put into compost piles. Avoid composting the following materials:
CHEMICALLY-TREATED WOOD PRODUCTS
Sawdust is often available from constructions sites, friends, or your own building projects. If you are considering composting sawdust, be sure of the origin of the sawdust. Sawdust from chemically-treated wood products can be bad stuff to compost. For example, take pressure-treated wood (sometimes called CCA), which usually has a greenish tint to it (I have also seen it in other colors). It contains arsenic, a highly toxic element, as well as chromium and copper. There is evidence to suggest that arsenic is leached into the soil from these products when they are used to make compost bins or raised beds, so composting the sawdust would certainly be a mistake. You may wish to read the 'Letters' section of Organic Gardening, April 1994 and July/August 1992, for more information. Avoid other chemically-treated wood products and sawdust as well, such as wood treated with creosote or 'penta' preservative.
DISEASED PLANTS
Many plant disease organisms are killed by consistent hot composting, but it's difficult to make sure that every speck of the diseased material gets fully composted. It's best not to compost diseased plant material at all, to avoid reinfecting next year's garden.
HUMAN WASTES
Human feces can contain disease organisms that will make people very sick. Composting human feces safely requires that the compost pile reach high (thermophilic) temperatures over a period of time. It isn't necessarily that difficult to reach these temperatures in a home compost pile, but the potential health costs of improper composting are high. Composting of human feces should not be attempted, except by experienced 'hot pile' composters who are well informed of the temperatures and times required to kill pathogens, and who are willing to take 100% responsibility for the process and product. If you would like to learn more about composting humanure, I recommend The Humanure Handbook, listed in the resources section of the Rot Web.
MEAT, BONES, AND FATTY FOOD WASTES
These materials are very attractive to pests (in an urban setting, this could mean rats...). In addition, fatty food wastes can be very slow to break down, because the fat can exclude the air that composting microbes need to do their work.
PERNICIOUS WEEDS
Morning glory/bindweed, sheep sorrel, ivy, several kinds of grasses, and some other plants can resprout from their roots and/or stems in the compost pile. Just when you thought you had them all chopped up, you'd actually helped them to multiply! Don't compost these weeds unless they are completely dead and dry (you may want to leave them in a sunny place for a couple of weeks before composting). Remember also that composting weeds that have gone to seed will create weeds in next year's garden, unless a very hot pile temperature can be maintained to kill the seeds.
PET WASTES
Dog and cat feces may carry diseases that can infect humans. It is best NEVER to use them in compost piles. Some people do bury them 8" deep in the soil, but ONLY in areas where food crops are never grown.
There are a tremendous number of options for containing your compost. Some people choose to go binless, simply building a compost pile in a convenient spot on the ground. Others build bins from materials such as recycled pallets, or two-by-fours and plywood. And, of course, there are many commercial bins on the market.
The question arises, "Which system is best?" Each system has advantages and disadvantages that you should consider when making your choice. However, there aren't many significant differences in actual composting performance between the various traditional bin systems (two exceptions might be worm bins and drum/turning units). More important to the success of your efforts is taking care to provide the proper environmental conditions for composting. Choosing a type of bin is much more a matter of asking questions such as, "How much kitchen and yard material do I have for composting?" and "What system best fits my preferences for neatness, attractiveness, and convenience?" If you're agonizing over choosing a recycled-plastic, dome-shaped detrital digester model for $259 versus building your own setup from $199 of lumber and hardware, you may wish to slow down before laying out all that cash, and make sure that what you end up with will really meet your needs. There are some very attractive and well-engineered commercial bins out there, as well as plans for excellent do-it-yourself models. But why not find out about all the options? Many people, for instance, are very fond of low-cost, attractive units built out of wooden pallets that are free for the asking from local businesses.
One very strong recommendation that I do have is to AVOID THE USE OF TREATED LUMBER when building a bin system. 'Pressure-treated wood' (also known as CCA), which commonly has a green tint, contains arsenic, a highly toxic element (it also contains toxic levels of copper and chromium). There is evidence to suggest that arsenic will leach into your compost if you use CCA lumber in the bin. Unfortunately, many extension services and local governments actually recommend using this stuff for building compost bins. If you are contemplating using CCA wood, please take the time to read the information in the 'Letters' section of Organic Gardening Magazine, April 1994 and July/August 1992, before beginning.
Possible Composting Systems:
One Bin Systems:
A one bin system is the simplest way to make a compost pile, and is a great way to get started. If you plan to make a lot of compost, one bin may not be enough capacity, but adding another can be a simple matter. The basic idea of a one bin system is to make an enclosure for your bin that is at least three feet (or about one meter) across, although you may also choose to use no bin at all if you don't need to keep everything tidy. Possible construction materials include free wooden pallets from local businesses, lumber, cinder blocks, or even steel posts and wire fencing. Once you've made your bin (or decided not to), you might build a pile all at once if you have the ingredients, but it's more likely you'll build the pile over time as you generate compostable materials.
If you build the pile over time, the stuff on the bottom will decompose first, since it will have been there the longest. When there is finished compost at the bottom of the bin, and you want to use it, simply remove the unfinished compost from on top, take out what you need, and throw the unfinished compost back on top. If your pile is not a high-temperature pile, you may want to let redworms (a kind of earthworm) help make the compost. They'll make the process go more quickly, and can create a very high quality finished product.
Two Bin and Three Bin Systems:
These systems consist of two or three adjacent bins, and may be made out of the same materials as a one bin system. The advantage of having more than one bin is that one can have a bin for the pile being built (as ingredients are accumulated over a period of time) and another one (or more) for a pile already built that is in a more advanced stage of decomposition. If you have the space for such a system, and are generating or gathering enough materials to keep the bins in use, this can be very convenient. When you start using a system like this, build your pile in one of the bins. When this bin becomes full, 'turn the pile' by transfering it to the adjacent bin (a garden fork or similar tool will help). This will aerate the pile and hasten decomposition. An alternative that I have found to be very successful is to let redworms do the turning 'in place' (this way I save myself labor and just leave the pile in its original bin). Whatever you choose to do, you can now begin to build a new pile in an empty bin while the first pile continues to decompose.
I find that a two bin system works well for me, but other people generate more compost or like to have a bin for storing finished compost, and therefore choose a three bin system. In a three bin system, you might start by building a pile in the leftmost bin. The original pile is turned into the middle bin when it's time to begin building another pile, aerating it to accelerate the composting process. Another pile is then built in the leftmost bin. When that pile is completed, the old pile (which is now in the middle) is turned a final time into the rightmost bin for finishing, and the just-built pile is turned into the middle bin, making the leftmost bin available for yet another pile. Finished compost will eventually be removed from the rightmost bin. Get the idea?
Rotating or Tumbling Systems:
The cost of these systems can be quite high, and they are somewhat small, but these factors are balanced out by the speed at which drum/tumbler systems can generate finished compost. Under ideal circumstances, compost may be finished in three weeks in a rotating drum composter! Fill the container partly full with a mix of greens and moistened browns, and then give the unit a turn every day or so to aerate the ingredients and remix them. It's important not to pack the container full, because the ingredients won't tumble and mix if packed in tightly.
While one batch is composting, you can accumulate the materials for the next batch. When the first compost is finished, you can dump in the materials you've saved to make more. It's possible to maintain relatively high temperatures in drum/tumbler systems even if they are small, both because the container acts as insulation and because the constant turning keeps the microbes aerated and active.
Sheet or Trench Composting:
This may be the ideal system for people that have garden space who don't want to fuss with bins and piles. Simply bury your kitchen wastes in a trench 8" deep dug in the garden, leave the buried materials to rot for a few months, and then plant above them. By the time you plant, the materials will have rotted into stuff in which plant roots will thrive. If you have copious amounts of materials to get rid of all at once, such as autumn leaves, you might want to spread them around the garden and rototill them into the soil (this is best done in the late autumn, or at least 2 months in advance of planting in the area).
Commercially Available Bin Systems:
Commercially available bins are typically somewhat expensive compared to do-it-yourself bins, but they do keep your compost neatly enclosed and can provide an 'instant solution' to the question of how to set up a composting system. In performance, many of the plastic bins may help to insulate the compost somewhat, allowing decomposition to occur later into the cold season. However, I don't feel that there are major advantages in the actual composting performance of commercial bins -- they function more or less the same as a one bin system (described above). A few brands seem to claim that they are able to harvest some kind of special cosmic energy or the power of the pyramids in assisting decomposition. Nonsense. They certainly can function just fine as compost bins, but there is no magic involved.
Many of the companies selling plastic bins manufacture them from recycled plastic. If you plan to get a pre-built plastic bin, keep your eyes open for ones made from reclaimed plastic -- support recycling and businesses that sell recycled products!
Clean Air Gardening - http://cleanairgardening.com - Compost bins, manual reel mowers and other environmentally friendly lawn and garden tools. Free US ground shipping!
Worm Bin Composting:
Maintaining an enclosed bin specifically for 'vermicomposting' is an excellent way to take care of food wastes. In fact, such a system can even be kept indoors. With the exception of holes for drainage and ventilation, worm bins for indoor use are typically completely enclosed, with a lid of some sort to cover the top. Outdoors, worms can be turned loose in a pile in your compost bin, or contained in a worm bin built specifically for vermicomposting.
Some municipalities, fearful of rodent pests and the diseases they may carry, discourage or even prohibit the composting of food wastes in open piles, recommending enclosed worm bins instead. A sturdy outdoor worm bin is protected from pests, and produces compost quickly during the warm season (or year-round in mild climates).
One of the challenges of beginning a vermicompost system is finding a source of worms. A typical earthworm from the garden won't do. Vermicomposting requires a species that is adapted to living in decomposing organic materials rather than in the soil. Two species are Eisenia foetida and Lumbricus rubellus. Also known as the redworm, manure worm, or red wiggler, Eisenia foetida is often available at bait shops (ask for red wigglers), but can be mail ordered less expensively from worm farms listed in the classified ads of Organic Gardening Magazine. Governments and organizations that promote vermicomposting may maintain 'worm banks' as a low-cost source of worms for the general public. Seattle Tilth, in cooperation with Puget Consumers Co-op, has a worm bank at a composting demonstration site in back of a PCC grocery store.
The general idea is to provide a cool, moist bedding (some kind of 'brown' compost ingredient such as shredded leaves or paperboard) for the worms to live in, and then bury kitchen wastes in the bedding. As bacteria and fungi begin to decompose the materials, the worms graze on the bacteria and fungi, and also break up the ingredients with their movement through the bedding. Eventually, the worms have ingested the ingredients and bedding, turning it all into worm castings (feces) that are an excellent finished compost.
Composting with worms is very easy to do, but there are a few basics of vermicomposting that are helpful to understand. I plan to provide a how-to guide some day. Meanwhile, you may wish to read the vermicomposting guide available on the World Wide Web from CITY FARMER, an organization in British Columbia.
Composting Resource List
The resources listed below are good for learning about composting. Often, the books are available at local libraries. Pamphlets published by cooperative extension agencies are often available from those agencies for minimal or no cost, for residents of the states or regions served by the agency. ISBN codes are included when available (ISBNs allow bookstores to quickly place special orders for a particular book).
Composting Info on the Internet/WWW:
• COMPOSTING NEWSGROUP/LISTSERVE: This is an open discussion, via email, of composting topics. To receive all of the discussion postings, send email with no subject or signature to listproc@listproc.wsu.edu. The message of your email should read "subscribe compost yourfirstname yourlastname"
• CITY FARMER: An excellent source of information on composting/gardening in urban situations. Includes a lengthy description of vermicomposting basics.
• In British Columbia, the Greater Vancouver Regional District has lots of good information about backyard composting.
• There is a large composting WWW site at Cornell University.
• Try out the vermicompost information site maintained by Brian Paley.
• Ontario recyclers and composters will want to learn about the activities and projects of the Recycling Council of Ontario.
• Chris Palmarini in California has published a composting information site on the web. Included is a WWW-based interactive 'bulletin board' for questions and answers about composting.
• The Spokane (Washington) Regional Solid Waste System has a web site with information on home composting.
• The student group SORROW at the University of Michigan is promoting composting on campus. They have written a feasibility study on the composting of campus food wastes.
• Recycling/Composting Links from - Advanced Life Support and Gravitational Biology at Kennedy Space Center ALS work at KSC concerns creating a bioregenerative life support system for long term space missions (naturally vegetarian at the moment).
Books:
BACKYARD COMPOSTING
published by Harmonious Press, Ojai, California, 1992 (ISBN 0-9629768-0-6). This is the simplest, most easy to read how-to guide for composting. It is short and very easy to read, yet presents all the basics.96 pp.
THE HUMANURE HANDBOOK
by J.C. Jenkins, Jenkins Publishing (P.O. Box 607, Grove City, PA 16127. $19.95 ppd., ISBN 0-9644258-4-X). The composting of human manure is controversial, or even outrageous, to many experienced composters. Joe Jenkins takes on the composting 'establishment' with this book, presenting a persuasive argument for why 'humanure' should be composted, as well as citing research to support the safety of his method. By carefully building a pile so that it reaches high enough (thermophilic) temperatures, and by monitoring the temperature of the pile over time, Jenkins argues that it is possible to safely compost human manure at home. Those with minimal experience in composting may find this book an interesting read, as it is very easy to understand. However, humanure composting should not be done unless one is an experienced 'hot pile' composter who makes an informed choice to take 100% responsibility for the process and its product. This is an important book in that it opens one's eyes to the loss of what should be considered a valuable natural resource. I found the book very interesting and helpful. Some may be offended by the terminology used. Nevertheless, I highly recommend this book! 198 pp.
LET IT ROT!
by Stu Campbell, Storey Communications, Inc., Pownal, Vermont,1990 (ISBN 0-88266-635-5). This is a good general how-to guide for composting. It's very easy to read, but includes considerable detail for those who want to learn more about the composting process. 152 pp.
WORMS EAT MY GARBAGE
by Mary Appelhof, Flower Press, Kalamazoo, Michigan, 1982 (ISBN 0-942256-03-4). Mary Appelhof is an expert with more than twenty years experience using worms to compost kitchen fruit and vegetable trimmings. Her book is the best source of detailed information on the simple art of "vermicomposting" kitchen wastes. Interesting reading, with cartoons, drawings, and diagrams. 100pp.
WORMS EAT OUR GARBAGE
by Mary Appelhof, Mary Frances Fenton, and Barbara Loss Harris, Flower Press, Kalamazoo, Michigan, 1992 (ISBN 0-942256-05-0). A resource book for teachers who want to try vermicomposting with their students. Activities are appropriate for grades 4 and above. 214 pp.
Pamphlets:
These booklets and pamphlets, or similar ones, may be available from cooperative extension offices in your state.
COMPOSTING TO REDUCE THE WASTE STREAM, Northeast Regional Agricultural Engineering Service, Ithaca, New York, 1991.
COMPOSTING YARD WASTE, Service in Action Bulletin #7.212, Colorado State University Cooperative Extension, Fort Collins, Colorado, 1991.
HOME COMPOSTING, Seattle Community Composting Education Program, Seattle, Washington.
RECYCLING YARD AND GARDEN WASTE, Circular #ANR-700, Alabama Cooperative Extension Service, Auburn University, Alabama,1992.
Periodical:
WORM DIGEST, P.O. Box 544, Eugene, OR 97440, $12/year (4 issues).Worm Digest is a quarterly journal that covers the use of worms in composting and soil improvement. This is a great journal for anyone seriously interested in worm bins, and especially for those interested in teaching others or spreading the word about vermicomposting.
Videos:
COMPOSTING FOR THE 90's - A REASON AND METHOD FOR EVERYONE
from Earth to Earth Productions, P.O. Box 1272, Burbank, CA 91507-1272 (approximately 50 minutes long, ISBN 1-881647-02-1). This video covers everything from why to compost, and different ways to make and use compost, to how composting can save money on garbage bills. Very easy to understand, and complete, yet concise. Recommended for new composters who like how-to videos and for public libraries/organizations that want to provide user friendly how-to resources for their patrons.
WORMANIA!
from Flowerfield Enterprises, 10332 Shaver Road, Kalamazoo, MI 49002 (26 minutes, with a 48-page teaching guide, $38.40, ISBN 0-942256-07-7). Mary Appelhof has produced, partly with the help of a National Science Foundation grant, this video on the subject of worms and vermicomposting. In the video, Worm Woman visits a family, teaches them about worm biology, and helps them set up a worm bin for composting kitchen wastes. Several worm-related songs by Billy Brennan make up part of the video, which covers a lot of ground in a concise fashion, but is entertaining and engaging. Microvideo is used to illustrate worm anatomy. Worm movement, feeding/digestion, and reproduction are all covered, as well as the role worms play in improving soil drainage and organic matter content. A great video for libraries, school districts, master composter groups, and agriculture or biology classes. This is not primarily a how-to video for vermicomposting (use Mary Appelhof's excellent book Worms Eat My Garbage for this purpose), but would be good for general outreach to promote the idea of vermicomposting, or as a supplement to how-to education.
Rot Web text (c)1996 by Eric S. Johnson