US Trends in Compost Technology

Compost has long been viewed as an important source of nutrients, organic matter, and plant protection. But as the garbage piles grow higher, broader and more numerous it is the economics of waste disposal that make composting an increasingly attractive option. Waste disposal costs are on the rise and reach $50-100 per ton in some areas of America, making recycling in general, and composting in particular, a necessity.

An individual American produces an estimated 1,300 pounds of trash per year. About 40% of that is paper, 20% yard waste, 10% food wastes, 10% glass, 10% metals, 10% plastic and miscellanous. At present, about 83% of America's waste is landfilled, 8% burned or incinerated, and 9% recycled, (OTA. 1989.)In response to the interest in composting there are now over 1000 facilities in America that compost yard waste, 120 plants compost sewage with 100 more in the works, and nine plants compost mixed municipal solid waste,(Glenn, J. , 1990.)

Alternatives to composting are expensive. Tipping fees to incinerate waste generally exceed $40/ton. Landfill fees can vary, and in some areas are less than $10/ton. The Northeast, however, leads the nation in landfill cost. Connecticut, Pennsylvania, New Jersey and New York average $70/ton, (Glenn, J., 1990.) 80% of the landfills in America are projected to close over the next 20 years as government regulations become more strict. Landfill and incineration costs will increase dramatically, (USEPA, 1989.)

Technology-From Industry to Backyard

Technological innovations focus on large-scale composting. Industry has rushed to fill the market for machines that will process large volumes of material. Many machines are designed for the standard windrow system in which materials are composted in elongated piles outside, machines such as: grinders, shredders, screens, etc. Efforts to optimize the composting process through increased monitoring and control include forced aeration, tunnel technology, and in-vessel composting. Forced aeration of static piles is designed for blowing air through ventilation pipes in sewage compost windrows. In-vessel or contained composting allows for environmental control and containment of odors. Tunnel technology used in the Dutch mushroom industry recirculates air from within the pile, recycling heat and gases produced.

Intermediate-scale composting is confined to smaller communities and farms, and primarily uses conventional farm-scale machinery to make compost in long windrows: front-end loaders, manure-spreaders, perhaps tractor-driven turners. Less new machinery or innovative engineering is reported at this level. The goals of intermediate-scale composters seem to be minimization of labor, cost, and odors generated rather than maximization of production efficiency.

Finally, small-scale composting is the realm of homeowners who deal with yard wastes: grass clippings, leaves, food, woody materials, and weeds. In the past, municipalities have collected these materials and disposed of them as landfill or stockpiles. Backyard composting is increasingly encouraged as a way to reduce waste volume. There is a thriving retail market for compost containers, starter inoculum, tools, and information. However, the technology of small-scale composting in aerobic piles is largely unchanged.

Rodale Trials

Rodale Press has published articles and books on composting since its inception in the 1940's. Recently, Rodale Research Center has conducted compost research as part of its initiative to study agriculture in areas undergoing rapid urbanization. Grants from the Pennsylvania Energy Office have funded studies of intermediate-scale compost production and utilization. Specifically, there have been four projects to date:

1) A feasibility study in two Pennsylvania counties of on-farm composting combining manures with urban and industrial wastes. The study inventoried compostable waste materials, farm-scale compost technology, state regulations, and local compost markets. Three hypothetical on-farm compost scenarios were developed, (Dreyfuss, D. 1990).

2) A research trial to demonstrate and assess the viability of on-farm composting farm wastes with a portion of the municipal waste stream. Poultry litter and leaves were composted using farm-scale machinery and methods during the winter months of 1989-1990. In addition, trial windrows were constructed of shredded newspaper and poultry litter, (Gresham, C. et al, 1990).

3) A research trial to compare corn yields and soil nitrate levels with six treatments (replicated four times): low rate of compost, high rate of compost, raw poultry litter, control, conventional fertilizers, compost plus sidedress fertilizer (In progress).

4) An ongoing project to study innovative designs for community development, focussing on energy conservation and waste management (In progress). In addition, two Pennsylvania state grants have been awarded to support education and outreach on backyard composting. On-site demonstration of composting options for homeowners will be developed, educational materials prepared, and outreach through state workshops implemented.


There are still gaps in the loop of organic materials recycling. These translate into entrepreneurial and research opportunities in the field of waste reduction:

1) Marketing and use of compost end product
2) Regional inventories of compostable products. Linking of waste producers with waste "consumers".
3) Establishment of compost quality standards.
4) Control of odors.
5) Recycling of human waste and separation of contaminants from the sewage stream.

Escalating disposal costs are fueling an expansion in composting of organic wastes, along with a surge in research and technological developments. Rodale will continue its longstanding commitment to compost as a cornerstone of waste recycling and soil health.

Office of Technological Assistance. 1989. Facing America's trash- what next for municipal solid waste/. OTA Publication O-424. $16. US GPO #052-003-01168-9.

Glenn, J. 1990. The state of garbage in America. Biocycle; March 1990: v. 31(3): 48-53. BioCycle is a journal which reports on the composting field: JG Press; Box 351; Emmaus, PA 18049.

United States Environmental Protection Agency. 1989. The decision maker's guide to solid waste management. USEPA Publication 530/sw-89-072. USEPA, Office of Solid Waste; Washington DC 20460.

For a copy of the report, Composting of Poultry Litter, Leaves and Newspaper, write to:

Cyane Gresham
Rodale Institute
611 Siegfriedale Road
Kutztown, PA 19530, USA