Beneficial use of biosolids
In the last 15 years, the federal government has passed legislation regulating biosolids management, limiting traditional methods of disposal – incineration, landfilling and ocean dumping – and making them more expensive than they once were. For example, the 1988 Ocean Dumping Ban Act, the Part 503 Biosolids Rule and the Part 258 Landfill Rule address, among other things, biosolids disposal and its effect on the environment.
As a result of regulatory changes, cities and counties are increasingly opting to recycle sludge rather than sludge rather than dispose of it. In particular, land application is proving to be an option of growing interest for local governments.
Since the enactment of the Clean Water Act nearly 30 years ago, the amount of municipal biosolids produced annually has nearly doubled. According to the U.S. Environmental Protection Agency, municipalities will produce an estimated 7 million dry tons of sludge in 2000, compared to more than 4.5 million dry tons in 1972. (The increase is attributed mainly to population growth.) EPA projects that, by 2010, U.S. cities will produce more than 8 million dry tons of sludge annually.
Prior to the passage of regulations limiting the number of pollutants and pathogens in biosolids, most of the sludge generated in the United States was disposed of in landfills. However, advancements in wastewater and biosolids treatment technologies – including wastewater pretreatment and pollution prevention programs – have improved the quality of biosolids, allowing local governments to develop beneficial uses for sludge.
The method by which biosolids are beneficially used depends largely on what is cost-effective for the community. According to Bob Brobst, biosolids coordinator for EPA Region 8 and manager of EPA’s Biosolids Data Management System, 50 to 60 percent of the biosolids produced today are applied to land as fertilizer or as a soil additive, up from 33 percent in 1988. “Land application has nearly doubled in 12 years, and I don’t see that changing,” he says. (For information on the Biosolids Data Management System, see the accompanying box.)
EPA also credits federal and state regulations and guidance – in particular the Part 503 Biosolids Rule – for nearly eliminating the disposal of biosolids in landfills and for encouraging biosolids recycling. EPA attributes the growth in biosolids recycling to public outreach and marketing; the high cost of biosolids disposal in some locations; disposal bans in some landfills; landfill capacity concerns; landfill closures; and additional research into the safe, beneficial use of biosolids.
Nevertheless, in some areas of the country, biosolids recycling is decreasing as local governments take advantage of low landfill costs. EPA is unsure whether those areas will affect the overall trend away from biosolids disposal.
Land application, which has been practiced for decades, involves spreading biosolids on the soil surface. When properly treated and processed, biosolids enrich soil and can supplement or even replace commercial fertilizers.
Historically, biosolids have been applied to agricultural crops, forests, parks and golf courses, and used in the reclamation of mines and other drastically disturbed sites. Composted and treated biosolids are used frequently by landscapers and nurseries and by homeowners for lawns and home gardens.
DeKalb County, Ga., is one of many local governments that have implemented a land application program for biosolids reuse. In 1991, as the county planned a wastewater treatment plant expansion, officials began looking for economic and environmentally responsible ways to recycle the biosolids.
The expansion included the addition of an advanced secondary treatment facility capable of treating 20 million gallons of wastewater per day. The plant currently produces 8,888 pounds of Class B dry solids each day, and the county applies it to a 550-acre hay field adjacent to the treatment facility.
The field produces 300 to 600 pounds of Bermuda hay per acre per year. Beef cattle, horses, mules, goats and even the elephants at Zoo Atlanta have benefited from the 12,926 tons of hay harvested during the past nine years. Additionally, by implementing the land application program, the county has saved more than 129,000 yards of landfill space.
Similarly, Taos, N.M., has saved landfill space by producing and selling pelletized biosolids for use as fertilizer. For years, the town had used lime to stabilize sludge and then applied it to a disposal site behind the treatment plant. However, in 1998, Taos was running out of land on which to dispose of the sludge, and the only remaining, affordable parcel was situated on the outskirts of town. The dilemma: either truck the biosolids through neighborhoods, angering the homeowners, or haul the sludge to the local landfill, which was quickly running out of space.
In the end, the town vetoed both options and turned instead to Biosolids Enrichment and Recycling (BER). The process takes dewatered sludge into a continuous flow process where it reacts in an enclosed environment with ammonia, acid and potassium, rendering the biosolids sterile and stable. The process produces Class A quality fertilizer.
By using the BER process, Taos has eliminated the need for lime stabilization, land application and permitting. The biosolids are sold in pellet form to farms, allowing the town to recover some of the costs of the treatment process and return the biosolids to the soil, where air and water break down the organic material.
In states such as New York and Massachusetts, where open space is nearly nonexistent and the distance to agricultural land is substantial, land application is largely out of the question. In those states, communities are hauling their biosolids to other states, where there is opportunity for reuse. For example, dewatered Class B cake biosolids from New York City and Class A pelletized biosolids from Boston fertilize land in Prowers County, Colo.
In fact, Colorado has the largest interstate land application program in the country. In 1998, 12,715 wet tons of biosolids were applied to land, and, in 1999, 36,875 wet tons were applied – covering nearly 40,000 acres in Prowers County. About 75 percent of that is applied to dryland winter wheat, while the remainder is used on rangeland, sand dunes, irrigated alfalfa and irrigated corn.
By involving the regional health department in the project, Parker Ag Services, the Limon, Colo.-based company that operates the project, has been able to build public support for importing biosolids. In each community that receives sludge, the regional health department monitors the process and oversees the land application program to ensure that it is being operated properly. “An informed and educated community is critical to the success of any land application program – especially one that transports biosolids two-thirds of the way across the United States,” says Mike Sharp, director of program development for the operating company.
Ultimately, the public’s perception of the safety and value of biosolids recycling will have a major impact on a community’s ability to market biosolids usage and products. Many current programs – including that in Prowers County – would not be successful without public buy-in.
To overcome public resistance to biosolids reuse, local governments must include education in their beneficial use strategies. For example, they should hold town meetings, conduct open houses, work with the media and provide the public with information resources. (See the story on page 72.)
Steady gains in recycling
According to EPA, of the 7 million tons of biosolids generated in 1998, 60 percent was beneficially used (land applied, composted, used as landfill cover), and the rest was disposed of with no attempt to recover nutrients or other valuable properties. EPA estimates that, this year, 63 percent of the biosolids generated will be beneficially used, and it expects growth in biosolids recycling to continue. In fact, the agency is estimating that 70 percent of all biosolids produced in 2010 will be beneficially used.
Part of that growth will depend on the development of new technologies. For example, technologies exist that can transform organic waste to raw materials for industrial use. Many processes are advancing from the pilot test stage and nearing commercial use.
Additionally, growing acceptance of beneficial use of biosolids could lead to increasing biosolids recovery in the future. Effective public outreach and educational programs may make biosolids usage as acceptable as recycling the daily newspaper and soft drink cans.