Joe E. Heimlich
For centuries, farmers have been plowing stubble from crops back into the soil. Likewise, farmers in many agrarian societies have long used animal manure as fertilizer on their fields. These historic actions provide contemporary society with a base for composting, one of the components of an integrated waste management system.
Composting is the biological reclamation of organic materials by a natural decomposition process. Examples are decay of fallen leaves in forests, decay of wood in a stand and animal carcasses decaying in a preserve. These natural processes in nature return organic material to the ecosystem.
Leaves bagged in the city or food waste from the table are not naturally components of the ecosystem. These components contribute nearly a quarter of the waste going into landfills. Furthermore, the wet quality of food and organic waste in household refuse adds liquid to the waste buried in landfills which can contribute to the potential leachate of the fill. organic wastes are components of our garbage and these items have to be disposed of in the best possible manner.
The organics in the nation's trash basket arc a mixed lot. Yard wastes include grass clippings. fallen leaves, garden and flower bed plant remains, weeds, Christmas trees. and trimmings from hedges. Food wastes are perhaps the most common and visible of organic wastes in household trash. Also included in organic waste are paper, wood scraps. and some fiber materials.
Yard wastes alone contribute between 15 and 20 percent of the solid waste generated by a city This includes household bagging of leaves and discarded Christmas trees. leaf collection programs, utility company tree trimmings. and refuse from parks departments.
Most urban organic waste currently goes into landfills where it occupies valuable space and adds direct costs of as much as $60/ton for collection, hauling and disposal. If urban organic wastes were not landfilled, there would be six full years of life remaining for every five years of landfill life currently projected. It makes sense to remove the organic materials from waste going to landfills.
Compost results In a physical breakdown of organic matter layered with small amounts of soil By a process known as aerobic disintegration. the structure of the matter is broken down by bacteria and fungi of decay until it is part of the soil mass. For example, a piece of newspaper would, under ideal conditions, become a part of the humus in the soil within two to four weeks. A tin can biodegrades in about 100 years; an aluminum can in about 500 years.
Even though the basic premise of composting is simple, the number of successful composting programs is small. It may be useful to explore the 'backyard' compost pile before examining large scale compost programs.
A household's compost pile includes such things as leaves. plant refuse, vegetables parings, weeds, wood shavings, lawn clippings, and non-greasy food wastes. Also layered in the pile is commercial nitrogen fertilizer to expedite the decay process and ground limestone to balance the pH. The pile is kept moist and periodically is turned to aerate the mass and mix the materials for better decomposition.
Household compost is usually used as a soil conditioner. It helps aggregate soil particles, adds some nutrients, and increases water holding capacity. (For more information, see Extension Fact Sheet HYG- 1008-84 Compost Production and Use; or Extension publication 4-H Program 918-A Camp Packet Compost).
Historically, composting plants established in the United States have met with little success. The process of composting on a large scale differs from household composting. It is important to control the methane gas that develops during decomposition (as in a landfill) and prevent leaching. Yet, there are success stories.
Cleveland, Ohio, has for several years maintained a fully self-supporting leaf compost project. Altoona FAM, Inc. in Pennsylvania maintained a successful compost program for many years. The technology for composting is well advanced and there are no significant problems in producing compost; the problem is in finding adequate use for the compost material.
The mass sort process of most commercial composting provides a rough mix of grades of paper, wood, fiber, food scraps and miscellaneous other materials. The irregularity of the materials going into the compost process suggests that what comes out is also irregular. This irregularity of material is reflected in particle size, purity of the compost, and usability of the end product.
The downfall of most commercial compost facilities is the lack of markets for the end product. There appears to be consistent discrepancy between the quality and the perceived value of the compost. Co- composting (mixing yard wastes with sludge from sewage treatment facilities) provides a high-quality soil additive but this product cannot be used on vegetable gardens and tuber, root or leafy crops. Use of co-compost in other fields is acceptable if the compost is monitored for heavy metal content. The irregular quality of the mass- sort compost makes it a difficult product to market. Greater effort is needed to create a sustainable quality and quantity of product and market match.
It is as expensive to landfill a bag of leaves as it is to landfill a bag of plastic containers. The difference in economic terms is that the leaves may not need to be landfilled because they may be resumed to the soil by composting.
If yard wastes, Christmas trees. and tree trimmings are treated separately from other organic wastes in the waste stream, composting may be an economic alternative and is an important component in an integrated waste system.
Most of the yard wastes are separated from other household and commercial waste and could be collected and treated separately as well. Many of these yard wastes are seasonal grass clippings in the summer, leaves in the autumn, trees in early January and therefore could be handled in a manner different than other wastes. If kept apart from other wastes, these particular organic wastes are a natural part of the ecosystem. It is in the contamination of these organics with household/commercial refuse organics that many problems arise.
Composting of selected organic materials can be a valuable component of an integrated waste management system. It is a process as natural as nature and as technologically advanced as recycling. There is no question that composting will be important in the future. A significant question is rather how and to what degree will composting be integrated for maximum value recovery.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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