O&M

Innovative Energy Systems’ Landfill l Gas Plants

Issue 6 and Volume 109.

There are nearly 400 landfill gas (LFG) power plants in operation in the United States, with nearly 100 more at some stage of development or construction. Innovative Energy Systems (IES), an LFG facility owner and operator based in Oakfield, N.Y., is on the leading edge of LFG commercialization and is taking advantage of emerging renewable energy credit markets to further enhance profitability.

IES currently operates three LFG plants in New York. Seneca Energy II, which came online in March 1996, houses 14 Caterpillar 3516 engines and is rated at 11.2 MW. Model City Energy, online in June 2001, houses seven Caterpillar 3516 engines and is rated at 5.6 MW. The Ontario County facility, online in August 2003, houses seven Caterpillar 3516 engines and is rated at 5.6 MW. Expansions in 2005 at Seneca Energy and Model City will add four Caterpillar 3520 engines to each location, raising capacity by 4.8 MW. Two new sites in Rodman and Cohoes, N.Y., will add another 4.8 MW each. Only the Model City facility operates in cogeneration mode – a greenhouse receives 31 MMBtu/hr of hot water – but greenhouses are slated for development at the remaining LFG facilities in 2006 and 2007.

“Each of the landfills where our plants are located are permitted for at least 18 more years of waste delivery and will operate for another 20 years after that,” said Peter Zeliff, IES president and CEO. “For 2004, we had an online availability of 99.2 percent and a capacity factor of 96 percent. Our average cost to produce power was 2.1 cents/kWh.” All the IES plants function as merchant facilities and sell into the day-ahead wholesale energy market.

In 2005, IES is selling 12 MW into the NEPOOL market. The rest of the production is sold into NYISO. As a qualifying renewable energy facility, IES generates renewable energy credits (RECs) that investor-owned utilities can purchase to meet renewable production obligations. The majority of IES’ RECs are under contract to Massachusetts and Connecticut utility companies, but an excess typically exists, which IES now sells into New York. “We were the first to move energy across New York State and into an adjacent control area,” said Zeliff. “No one had done this before, so it took some time to wade through all the red tape. For 2005, however, all of our excess RECs are contracted into NEPOOL.” IES has worked with Conservation Services Group to facilitate the REC trades. CSG identified partners, worked with the state and the Independent System Operator to handle imports, and resolved regulatory and legal issues so IES could enhance the value of their assets. 

IES has come a long way. Its first plant, Seneca Energy, was developed as a PURPA facility, with the energy sold at the utility’s avoided cost (an average of 2.2 cents/kWh). In 2004, IES’ three plants averaged 4.9 cents/kWh for the energy sold into the wholesale market and another 4.8 cents/kWh for the RECs.


The Seneca Energy II landfill gas plant in Waterloo, N.Y., houses 14 Caterpillar 3516 engines.
Click here to enlarge image

Because of the variability in landfill gas quality, gas clean-up is a top priority. “Most LFG plants use air over-coolers and coalescing filters to remove water and acids from the gas,” said Zeliff. “We clean the gas using a proprietary low-pressure refrigeration and absorption process that has enabled us to achieve double the engine life between major overhauls compared with the industry average.”

IES also practices preventive maintenance. The LFG plant personnel perform oil changes and engine tune-ups every 1,800 hours. If operational records indicate that any engine part has shown considerable wear, a maintenance schedule is set up to replace the part and send it to the shop for rebuild prior to failure. Candidate parts include the engine water pumps, waste gates, after-cooler cores and engine starters.

A key challenge at LFG plants is dealing with siloxanes in the landfill gas. Siloxanes are gaseous silicone compounds that can form silicone deposits in the combustion cylinder. Catalytic converters can’t be used in LFG applications because the silicone in the exhaust will coat the catalyst material within 24 hours, rendering it useless. Tight control of the air-to-fuel ratio, therefore, is essential in keeping emissions below regulated levels. IES has developed an automatic air-to-fuel ratio controller that maintains a lean combustion environment, ensuring emission compliance. The controller also enables IES to compensate for the varying heat content of the landfill gas, which can fluctuate between 350 Btu/ft3 and 600 Btu/ft3.

The IES landfill plants are staffed eight hours per day. The computer system controls the plants when staff is not present and alerts staff if a problem arises when unmanned. All IES personnel are trained to operate the power plant and also to monitor and adjust the landfill gas collection system. If the oxygen content of the landfill gas begins to rise in a particular well, for example, air is likely being drawn into that well, which could lead to spontaneous combustion. The operators monitor the gas collection system using a handheld gas analyzer and adjusting throttling valves at the well-heads.

“Our biggest challenge today is keeping up with the markets for the commodities sold from the power plants,” said Zeliff. “The wholesale market under deregulation is in its early stages and the market is changing on a daily basis. Being able to stay one step ahead of the market has become a full time job in itself. The REC market will be around for a while, but the prices received for RECs will drop dramatically over time. We built the company without any assumed REC income, so we know we can operate in a market with energy sales only.” p