Power Generators at Coffin Butte
Five counties in Oregon contribute 550,000 tons of waste per year to Coffin Butte. Currently, Pacific Northwest Gas Company (PNGC) owns and operates the Gas Recovery Plant at Coffin Butte landfill. PNGC utilizes three 820kW generators to create electric energy from the landfill gas (PNGC Power). Approximately 2,000 average sized homes can be powered off the 2.5 Megawatts per hour per year that the landfill produces (Hinton). Although the benefits of these methane powered engines greatly exceed those of just flaring the off-gas, the 20% efficiency could still be increased by changing to a fuel cell system to create the electricity. The combustion process produces pollutants that a fuel cell would not, such as NOx and SOx. Also, the US Environmental Protection Agency estimates that the 6,000 US landfills contribute 450-650 billion cubic feet of methane per year (Gas Separation Technologies).
Documents:
Sustainable Engineering Symposium Poster
Project Scope
Removing all sulfur compounds down to less than 1 ppm from the landfill gas stream is essential to implementing fuel cell technology at Coffin Butte Landfill. The landfill gas straight out of the "hill" contains approximately 500ppm H2S. These sulfur compounds are poisonous to the fuel cell membrane. The current understanding of the landfill gas is that H2S is the only sulfur compound at a poisonous concentration. This project will focus on two different methods of removing the H2S (silica gel beds and a bioreactor).
Silica Gel Beds
Two silica gel bead packed bed systems will be designed and built, a two dimensional bed and a cylindrical bed. These will be taken out to Coffin Butte multiple times to test the capacity of silica gel beads to remove H2S and the reproducibility of the data collected. A comparison between the two column designs will be conducted in terms of efficiency of removal of H2S.