Composting is nature's way of recycling. It is a controlled biological reduction of organic wastes to humus and is a simple, low-impact process which reduces greenhouse gas emissions, resource consumption, and waste. The end product, compost, is used as a soil amendment that enriches soils by providing plants with nutrients, supporting beneficial soil life, reducing soil diseases, increasing water retention in sandy soil and adding drainage to clay soils, promoting weed and erosion control, and providing a safe and sustainable alternative to petrochemical fertilizers.
Benefits of Composting
Organic materials make up a large percentage of a university waste stream. Composting provides an alternative to incineration or landfilling organics, which can be quite dense, have a high per ton disposal cost, and release significant sources of methane when decomposing in a landfill, thereby contributing to global warming. Compost improves soils water retention, aeration, and adds lost nutrients. Composting can save your grounds department money on buying mulch, fertilizer, and pesticides. The system may be worked into the curriculum of courses such as sustainability, biology, soil science, and ecology.
Compostable materials include organics such as grass, leaves, tree limbs, shrub waste, non-hazardous animal lab waste, hand towels, paper plates, napkins, wax and paper cups, wax and non-wax cardboard, pre and post-consumer food waste such as coffee grounds, tea bags, egg shells, and fruit vegetable, and grain waste.
College campuses have countless opportunities for collecting compostable materials: yard and leaf waste; pre-consumer food prep; post consumer food, and compostable food ware. Building composting systems into campus operations is a vital part of reducing campus waste and greenhouse gas emissions. Incorporating composting into all campus grounds operations, campus food service areas, catered events and other campus festivals, conferences, and athletic events is an important part of minimizing the campus waste stream.
Non-compostable materials include oils, weeds, diseased plants, meat, bones, dairy products, cat, dog, or human waste, hazardous materials, plastic, glass, metal, treated wood, and very large items like large tree limbs or stumps.
Contractors and Farms
Hiring a contractor to manage a college composting program could be a possibility depending on where the school is located and if such contracting services exist. Farms may accept yard waste for composting. Hog farms have been known to accept food waste as feedstock. Contact the local City or County; some areas have composting programs set up especially for yard waste. More and more communities are implementing local composting programs that will also take pre and post consumer food waste and compostables (such as paper foodware and compostable bioplastics). Local food banks may accept donations of food for the hungry and take food that has cooked but was not served. In any of these cases, the most important thing is to make sure the organic material is separated correctly and meets the accepting entity's specifications.
Control the following parameters of a compost pile: carbon and nitrogen inputs, size, surface area, moisture, air, volume, and temperature. The compost pile is full of microbes such as bacteria, protozoa, and fungi. Microbes need food, air, and water for survival.
What and how you choose to compost depends on many factors including space, funding, local land use regulations, and available labor. Composting space requirements can vary from as large as several acres to as small as a parking space. Common methods include grasscycling, hot or cold piles, long rows (windrows), in-vessel, and vermicomposting.
Piles can be any size and either contained or uncontained. It will take a longer time for a smaller pile to decompose because it will not generate as much heat as a larger pile. Make the pile no taller than the person working on it unless heavy equipment will be used. The pile will shrink and spread out over time. To contain it, build or buy a compost bin. A circle of chicken wire will work, as will a more elaborate wood bin, or store-bought plastic or wood bin from a garden store. Piles are usually used for small scale composting although they can be as large as cars. Depending on what is put into a pile and how it is managed, a pile it can take up to a year to yield finished compost, but generally produces finished compost on a much shorter time frame.
Aerated piles are made the same way regular piles are made except these piles have systems to facilitate more air flow. Such systems can be as simple as a pallet under the bin or as elaborate as PVC tubing with forced air inserted into a compost pile. More air generally speeds up composting processes.
Windrows can handle tons of organic matter. This type of pile is usually long, narrow, and at least four feet high. When implemented on a large scale, heavy machinery such as a front-end loader and/or windrow turner is usually required. Windrows can be covered or uncovered. This method is often used for large institutions, cities, and counties.
Tumblers are composting containers that rotate or turn. Some work is done manually, other work utilizes a motor. These units work by allowing the contents to heat up rapidly and retain moisture. Air is limited, but present. This method is best for small-scale, fast composting. Tumblers are available for purchase at garden stores and home improvement centers.
In-vessel composters can compost anywhere from a few hundred pounds to over 60 tons a day. Organic waste including meats, oils, fish, and dairy products are placed in the container and mixed, shredded, and fluffed by the composter. Some composters are fully automated with sensors to monitor temperature, oxygen, and moisture. Biofilters are used to reduce or eliminate odors. This method is most appropriate for institutions that generate large quantities of organics.
Vermicomposting uses red wiggler (Eisenia foetida) worms to do the work of composting. Vermicomposting requires air, water, and food the same way aerobic composting does, but in this case the worms (rather than the heat produced by the microbes) do the bulk of the composting work. The worms eat the organics and leave behind castings which can be used as nutrient rich plant food. These systems are available in a variety of sizes. A ten gallon container can handle a small department's food waste. A continuous flow system could handle a large institution's food waste.
Once a composting method has been selected, the next step is to determine how to transport materials from the source to the composting operation. For yard waste, determine what is currently happening with the material, the amount generated, and how the campus grounds crew collects and transports yard waste. If grass is currently bagged, how will it be incorporated into the composting system? The grounds crew might have a routine for the entire year that can be reviewed to determine how much and what kind of material is generated. For example, lots of tree or bush cuttings are typically generated at one time of the year and more grass and flower waste during other times. Is there enough carbon material to mix with the nitrogen material? Some composting operations have to find alternative sources of carbon and nitrogen. Collection systems will depend on volume. Regular trucks (including trash and dump trucks) may be utilized to collect and haul material.
If there is an opportunity to compost food waste and animal lab waste, find out how the waste is currently handled and determine how much waste is generated. Determine whether the system will handle only pre-consumer food waste or both pre and post-consumer food waste. Determine what type of animal lab waste is acceptable for composting. Make sure to only collect non-hazardous animal lab waste. Research any regulations concerning this type of waste.
Select sturdy bins that have lids and wheels and place the bins in strategic locations in order to collect the greatest amount of material. With a small amount of material, the collection system can be very low-tech. A 30 or 40 gallon bin with a lid and wheels would probably do the trick for collection. Depending on the situation, a can liner may need to be used in the bin.
Keep in mind safety issues concerning lifting because food (including lots of liquid) and animal waste can be heavy and awkward to move. Make sure to designate a place to clean out bins between uses. Color code and label bins clearly. For bin transport in a vehicle, make sure the lid is on tight and the bin is strapped in. For large-scale operations, use larger bins such as 60 or 90-gallon containers with lids and wheels. Assess the need to use heavy machinery and hydraulic systems. Examples include but are certainly not limited to: using a rear, top or side loader sealed trash truck to set up an all-organics collection route, using a dump truck for yard waste, using a hydraulic lift on a truck to empty 90 gallon carts, and having a tank full of water on the truck for cleaning out empty carts on site. Regardless of how the waste is collected, be reliable in picking it up. Food and animal waste cannot sit around waiting to be collected. Set a schedule and stick to it.
To institute a composting program in a dining hall that feeds hundreds of students, education is the key to success. Signs are a must and adding photos can help as well. During the first few weeks of school, designate a volunteer to stand by the collection bins to explain the new program. For events composting, station volunteers at sites for monitoring and educate the public about what is acceptable for campus composting. In campus kitchens, educate staff and managers. Provide periodic refresher presentations because of changes in the student body and staff. Brochures and posted guidelines are a helpful reminder as well. Include materials in new student trainings and orientations. If possible, take the staff (especially anyone who is involved in the composting process) out to the composting site to explain the process, savings, and resulting applications.
Finished compost should be fine, dark, sweet smelling, have a pH that is 7.0-9.0, and no longer be heating up. Depending on the methods used and the materials composted, it may be necessary to screen the compost to take out larger pieces that have not fully decomposed. Determine how fine to make the end product based on its intended use. Compost can be used as mulch around shrubs, trees, flowers and on paths, as soil amendment to break up clay type soils or bind sandy soils, as a lawn top-dressing, or for potting soil for house plants. Many people use compost in gardens instead of chemical fertilizers to provide nutrients to plants. It is also commonly thought that using compost can reduce or eliminate the need for chemical pesticides. Placing finished compost in a cloth bag and soaking it in a bucket of water for three to five days makes compost tea, a nutrient rich, liquid plant food.
Funding is usually the first concern for any project. How much to budget will depend on the degree of technology to be used. Site concerns are important especially in urban areas. Be sure to educate the neighbors; let them know what is happening, why there is a composting site, and invite them to participate if possible. Controlling odors is very important. Composting will not create unpleasant smells it the piles are managed correctly. Research the regulations that may apply to performing a composting operation on the chosen site. State or local ordinances may allow composting, but only using certain methods. Compost can be tested to assess the variety of nutrients in the finished product. This will help to determine correct concentrations when applying compost and will also be a useful aid in trouble-shooting any problems that may arise.
Animal Bedding Recycling Fact Sheet (
City Farmer Urban Agriculture Notes
Composting for Kids
Earth 911 Composting
Environmental Benefits of Composting (
University of Oregon- Composting/Food Services