Rock (Bio) Solid

Ron Delo

LIKE MANY COMMUNITIES IN THE NATION, New York's Rockland County once was faced with shrinking landfill space and more demanding environmental regulations. So the county developed a disposal solution that not only capped the costs of shipping biosolids out of state, but has since put the community on the leading edge of recycling sludge as a soil amendment.

Rockland County, once a rural farming community, is now a densely populated suburb of New York City. When the last landfills in the county closed in the 1980s and early 1990s, the community was required to export most of its solid waste. However, the Rockland County Solid Waste Management Authority (RCSWMA) recognized this was a short-term and potentially costly waste management solution. Thus began its search for a more self-sufficient plan that simultaneously would give the local entrepreneurial spirit a boost.

With the support of key county leaders, the authority acquired a 38-acre site in Hillburn, N.Y., on which to develop its recycling and composting center. Officials believed the site was ideal for solid waste and biosolids disposal, and they constructed a plan calling for four new facilities; a waste transfer station; a recyclable pre-processing facility; a materials recovery facility (MRF); and an in-vessel co-composting plant.

In February 2000, The Rockland County Recycling and Composting Center (R₂C₂) began operating Palm Desert, Calif.-based USFilter's IPS Composting System to process clean wood waste and biosolids, the residual from wastewater treatment plants. Using an aerobic process that meets U.S. Environmental Protection Agency (EPA), Washington, D.C., requirements, the biosolids are decomposed into a humus-like substance and used as a fertilizer or as a soil additive.

Composting Technology

Biosolids from the five Rockland County wastewater treatment plants, as well as from three out-of-county wastewater treatment plants, are hauled to the fully enclosed, 50,000-square-foot-facility, which also provides onsite wood-waste shredding. There, biosolids are mixed with ground-up, clean wood waste and placed in nine concrete, bin-like bays. The bays, each measuring 215 feet long by 10 feet wide by 7 feet deep, are capable of receiving 300 cubic yards of mixed waste material each day.

A computerized temperature-sensing system introduces air from the bottom of the bays through a network of perforated piping to stimulate decomposition and the release of water, heat and carbon dioxide from the organic material. The enclosed design also enables exhaust from the system to be contained and collected to minimize foul odors. The compost building is maintained under negative pressure, and all exhaust air is sent directly into the odor-control biofilter.

The material is processed in the bays for 14 to 21 days and then transferred to an aerated curing area inside the same building where it cures for up to 39 days to ensure odor is controlled and mature compost is produced. Once cured, the compost is transferred to a 27,000-square-foot partially covered screening, storage and distribution building.

Based on origin and date of delivery, a computerized tracking system enables operators to locate any batch of materials as they progress through the system. Batches that exceed metal limitations can be removed and disposed.

Finished compost is ready for commercial sale for agricultural and horticultural use within 50 days, the authority says. R₂C₂ has the capacity to convert more than 108 wet tons of biosolids and 60 tons of clean wood waste and other shredded waste material per day into compost

All of the compost produced at the composting facility since it began operation has been marketed and sold. In 2002, Rockland County received $30,600 for its share of the compost. Revenues are split 50-50 with Houston-based Synagro, which operates the facility.

Composting Community

By composting organic waste into fertilizer-like material for use on recreational fields, golf courses, landscaping and garden centers, the authority has reduced the cost for waste disposal and eliminated the need to send material to landfills. Moreover, by recycling biosolids, the authority is enriching the community's soil and saving taxpayers money.

According to the RCSWMA, the cumulative costs for each wastewater treatment facility to dispose of its sludge in 1985 was more than the cost of processing biosolids at the co-composting facility today.

To increase revenues, facility leaders have made proposals to accept and process biosolids, including sludge from potable water treatment facilities, from communities outside the county.

Rockland residents initially were wary of accepting outsiders' waste. However, because of the successful operation of the facility during the first year of operation and the potential financial benefits, the operation was expanded to also process out-of-county biosolids from several surrounding municipalities.

Based on the facility's success, Rockland County became the New York State pilot location for the Global Action Plan's Sustainable Lifestyle Eco Team Program in March 2001. The Authority also has received awards from the New York Water Environment Association, Syracuse, for its facility, which the authority says is the largest in-vessel biosolids composting facility in New York. But more importantly, outreach efforts and the effectiveness of the composting facility have created jobs in the community while enhancing awareness about the environment and waste-to-resource practices, the authority says.

Ron Delo is RCSWMA's executive director and is president of the Mid-Atlantic Biosolids Association, Philadelphia.