In 2000, the Northern Tier Solid Waste Authority (NTSWA) installed a system at its Bradford County, Pa., landfill to convert methane gas generated by decomposing waste to electricity for use at landfill facilities. Once the system was in place, NTSWA officials realized it was producing waste heat that could be used productively. So, last year, the authority constructed a greenhouse on the landfill grounds and contracted its operation to a hydroponic farmer, who is producing thousands of plants daily.

The landfill gas collection system includes more than 70 wells within a vacuum-based grid to pull methane (which previously was flared off) into a CAT 3516 reciprocating engine. A water-cooling system prevents the engine from overheating, and the resulting hot wastewater is pumped to the greenhouse at a rate of 80 gallons per minute through insulated steel pipes. The hot water runs through overhead radiators to heat four raised ponds in which leafy greens and herbs, including arugula, romaine and basil, are planted and harvested by a private farmer without the use of any pesticide or herbicide. The cooled water is circulated back to the engine.

The electricity from the engine — enough for more than 700 homes — powers the landfill's leachate treatment plant, the engine building and the 14,400-square-foot greenhouse. The agency sells any surplus electricity to the local power grid.

The farmer oversees the greenhouse's year-round operations, including the management of greenhouse staff, and harvests plants approximately 35 days after planting. Even though full production capacity (estimated at 7,250 plants daily) has not yet been reached, the project's revenues are increasing. On average, 3,000 plants are harvested and planted each day, and the plants are sold to local retailers and wholesalers who distribute the products throughout the community.

Funded partially by a $70,000 “Energy Harvest” grant from the Pennsylvania Department of Environmental Protection, the project, from concept to first harvest, took just under 14 months. The facility is self-sustaining, using public power only as a back-up energy source. In addition to harnessing the waste heat from the landfill gas engine, the greenhouse promotes agricultural employment in the area, exhibits sustainable agriculture and demonstrates the viability of public/private partnerships in the waste industry.

Project: Greenhouse public/private partnership

Jurisdiction: Bradford, Sullivan and Tioga counties in Pennsylvania

Agency: The Northern Tier Solid Waste Authority

Vendors: None

Date: December 2006, with official operations beginning in January 2007

Cost: $500,000