The nation's first commercial-scale biological reactor soon will produce its first kilowatt hour of electricity due to pending final negotiations between Rabanco Co., Bellevue, Wash., and Klickitat County (Wash.) public utility district (PUD).
This is how it works: Water will be added to Rabanco-owned Roosevelt Regional Landfill's municipal solid waste (MSW) to speed its methane production. Then, the gas will be captured and the electricity generated with a series of 1.6 megawatt internal combustion engines, the number of which can be increased as gas volumes grow.
Four engines will be used for the first installation in mid-1998. And, by the year 2014, gas volumes are predicted to supply more than 60 mega-watts of power.
"Adding water to the solid waste more than doubles the amount of gas produced in a dry environment," explains Rick Morck, Rabanco's senior vice-president. "That additional gas is collected, and its energy value is re-captured for public benefit.
"Over the landfill's life," he continues, "this equals about 8 trillion kilowatt hours of additional power produced - enough to provide power to more than 31,000 homes over 20 years."
The sale of electricity produced at the landfill, however, will depend on the increasing popular "green power" concept, in which customers can pay a premium on their monthly bill for the purchase of electricity from such sources as solar, wind or landfill gas. Regardless, the PUD believes that the methane will be able to compete well in the near future, even in the low-cost Pacific Northwest market.
In addition to electricity production, Morck says, the biological reactor concept has many benefits. "Other landfill gas components, like carbon dioxide or waste heat from power production, can be exploited for their commercial value. It gives us one more kick at the recycling can - even greater reuse and recycling of solid waste."
Studies also have concluded that microbes consuming solids in the pile will create more airspace in the landfill.
Additionally, the benefits extend to the landfill's closure. "We leave a safer environment because the pile has decomposed more completely," Morck says.
The regulatory change allowing water addition, pursued by Rabanco engineers immediately following the landfill's construction, is the key to the project's economics, says Ward Sanders, president of Seattle-based Power Management Corp., which worked with Rabanco on the landfill project. (Roosevelt Regional was constructed with methane recovery systems factored in from its conception.)
"Every kilowatt hour you can create earlier in the project [has] greater net present value than electricity produced 10 or 15 years later," Sanders says. "[Adding] water to the solid waste makes what might have been a project for the next generation today's project, justifying [an] investment with higher near-term revenues."
Rabanco's studies indicate that each 100,000 tons of solid waste produces about 13,000,000 kilowatt hours of electricity. The yearly permitted capacity of Roosevelt Regional Landfill is 3,000,000 million tons.
Though negotiations are still under-way, the tentative plan is for Klickitat County PUD to purchase Roosevelt's methane beginning in mid-1998, assisted by a grant from the U.S. Department of Energy's Renewable Energy Production Incentive Program.
The PUD will finance the generation equipment with tax exempt bonds and either use the electricity or sell it to other utilities. A request for proposals the utility sent out in mid-summer produced three responses from utilities in Washington State and California. Rabanco will share its net gas revenues with the county.
For the methane currently in the landfill pile, Rabanco will benefit from the Section 29 Federal Tax Credit Program until it expires in 2007.
Roosevelt Regional Landfill, located in eastern Klickitat County, is the center of the most extensive waste-by-rail network in North America and is the largest MSW disposal site in the Northwest.
For more information, contact: Rabanco, 200 112th Ave., N.E., Ste. 300, Bellevue, Wash. 98004. (800) 929-1195. Fax: (206) 646-2440.
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