Municipal solid waste composting: Has its time arrived?
Jeffrey H. Heath, P.E.
S&W Services, Inc.
Cazenovia, New York
In 2001 it was estimated that over 400 million tons of municipal solid waste (MSW) were generated annually in the United States on an annual basis (Biocycle—The State of Garbage in America, Dec. 2001). Public works officials throughout the country continue to deal with potential cost increases, shrinking disposal options, long haul distances, fluctuating recyclable rates, a greater public interest in expanding recycling programs, and the limited availability of land for new solid waste facilities.
Today, current disposal facilities primarily consist of "mega-landfills," incinerators, and waste-to-energy facilities. In response to more stringent regulations under the Clean Air Act, many of these facilities have completed significant and expensive retrofits, which have resulted in higher disposal fees. However, interest in MSW composting is on the rise, as evidenced by:
Given recent trends and successes, the present question for solid waste managers is whether composting has become a viable option for integrated solid waste management strategies. This question needs to be answered in light of specific requirements and goals. This article will offer intelligent discussion related to the benefits of MSW composting. For the remainder of the article, the word "composting" will be used to mean composting of municipal solid waste.
The history of composting has been relatively cyclical. For more than 40 years, European countries have had a history of composting. In the United States, earlier composting facilities struggled with inconsistent results, financial troubles, and skepticism among market end-users. Primary challenges for the earlier facilities included competing with low-cost landfill tip fees, inadequate investment in odor control systems, and quality control of the feedstock and compost end-product. Although during the 1980s and 1990s composting facilities were not 100% successful, new facilities began to further develop process controls and operating procedures that successfully controlled odors and improved compost quality. In addition, recycling initiatives and waste diversion goals supported the development of alternative technologies for minimizing the volume of waste that was to be disposed of at landfills and incinerators.
|Delaware County MSW Co-Composting Facility, Walton, NY|
Presently, the management of solid waste has several basic requirements. The first is to provide a reasonable level of service and price for waste management programs. The key factors driving solid waste management costs today are the reduction of available disposal facilities and increased haul distances to reach landfills or incinerators. The second requirement is to provide a sound environmental approach to managing solid waste. Current regulations are usually followed as a means to control environmental, safety, and health issues. The third is the need for controlling risk and long-term liability. Within state planning guidelines for solid waste, landfill disposal is often listed as the least desirable and as having the highest risk and greatest liability. The fourth requirement is to meet recycling/reuse/reduction goals for waste diversion. Through the 1980s and 1990s, the majority of this effort was focused on recycling, green composting (yard waste), and reduction of waste at commercial/industrial facilities. The "appropriate level" for participation in recycling programs has involved significant discussion among municipalities, since expenses can exceed revenue received from recyclable materials. In addition, public pressures for expanding recycling programs continue, while managers are faced with a diminishing return on investment as efforts are made to recycle products with low market value.
Municipal officials and solid waste managers who are contemplating a composting facility should consider the following:
Make no mistake that, in today's market, cost and cost control are the primary drivers with respect to solid waste management. Some of the key market influences for cost fluctuations include the costs of collection and hauling, disposal (tipping fees), labor and material and the availability of funding, contractual arrangements, level of service, and regulatory compliance.
The average tip fees for MSW landfill disposal vary significantly across the United States, ranging from $12 per ton in western states to over $75 per ton in some northeastern states. The most significant economic advantage for composting occurs when costs for recycling are factored into the overall solid waste management program. Many communities now face recycling costs of well over $100 per ton. Since composting facilities offer diversion rates of between 70% and 75% of the incoming waste, composting facilities allow solid waste managers to integrate this technology with their recycling programs to more effectively plan and control costs. With proper scaling, composting facilities can compete with a cost range of $60 to $75 per ton. Costs can be further reduced based on favorable work share programs, recycling grants, competitive utility costs or cogeneration opportunities, and strong markets for the composted product.
Through the 1990s, there has been continued regulatory interest in reducing and recycling waste. Under USEPA's hierarchy of solid waste options, landfilling is considered a less desirable approach than "reduce, reuse, and recycle" strategies. Currently, the main regulatory driver that promotes composting is the interest for organics diversion from landfilling. However, typically these diversion requirements have only been set as goals. Today, ten states have established diversion goals greater than 50%. Consequently, there are new incentives to promote alternatives to landfilling that increase diversion rates and favor reduction, reuse, and recycling.
There remains a genuine interest in developing new technologies for solid waste management. The primary objective in the past has been to close old and environmentally unsound landfills and to develop new landfills that meet regulatory requirements. Although many older landfills were successfully closed, other than incineration, there were no readily available alternative waste disposal sites. The technological advancements for composting have begun to dispel the concerns associated with these alternative sites.
Feedstock controls. Well-established recycling programs and household hazardous waste programs, as well as better tracking of hazardous waste, have allowed composting facilities to improve the feedstock quality, making it fairly easy to meet permit conditions or limits. In fact, some states have adopted procedures that allow unrestricted use of compost through a risk-based assessment.
Odor control. New facilities have successfully integrated sophisticated odor control systems within the composting facilities. Facilities today are totally enclosed, and there is significant emphasis placed on air handling and odor control. Although this effort comes at a price, it can be less than the alternative of long haul contracts.
|Bioreactor at the Delaware County (NY) MSW Co-Composting Facility|
Compost quality. In addition to feedstock controls, there continues to be more research and development related to process improvements for compost facilities. There is now a greater understanding of the time required to achieve maturity for compost, as well as the necessary operating parameters to achieve the desired quality. Compost is no longer just used for landfill cover—it is considered a marketable product. New processing equipment to eliminate inorganic materials from the compost continues to improve. In fact, the Conporec facility in Sorel-Tracy, Quebec, in continuous operation for more than a decade, is currently producing compost with an organic content of approximately 70%.
Compost markets. The ability to sell compost is directly related to the quality of the product. In the past, there have been significant concerns regarding the ability to beneficially reuse compost. With today's improvements in the end-product, it is becoming more and more of a viable soil amendment for site remediation, wetlands creation, erosion and sediment control, mine reclamation, manufactured soil amendments, and traditional landscaping uses. The beneficial use of composting can meet federal and state requirements of recycling content and will allow communities to achieve recycling rates in excess of 65% to 70% for their overall waste management programs.
As current waste disposal capacity is reduced, the need to develop new disposal options increases. The remaining capacities of landfills in the United States range from two years in northeastern states to greater than 20 years in the western states. Today, many communities are faced with the option of transfer and long haul or the unenviable task of developing and permitting a new disposal facility within their boundaries. With a diversion rate of greater than 70%, composting facilities can significantly extend the remaining life of existing landfills and can be sited at existing or closed landfills.
Composting is a viable enhancement to existing solid waste management programs. It integrates well within existing waste collection practices, as well as recycling programs. However, it also is recognized that, as a disposal option, it is currently not cost competitive in all areas of the country. Where MSW landfill tip fees exceed $60 per ton, or where recycling costs exceed $100 per ton, it is an option that should immediately be assessed.
Jeff Heath is Vice President of S&W Services, Inc., and a Principal of Stearns & Wheler, LLC. His responsibilities include development of MSW composting facilities that feature the Conporec Technology. He can be reached at (315) 655-4953 or at email@example.com.