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Farm makes history with "cow-powered" hydrogen fuel cell
Once an agricultural business starts thinking about renewable energy, it doesn't stop. A hog farm decides to build a wind turbine next to its anaerobic digester, or a feedlot realizes that its composting operation could fuel a new digester, or a dairy farmer wonders if his prize-winning digester could power a hydrogen fuel cell. "We want to prove that agriculture can produce energy as well as food," Dennis Haubenschild said of the demonstration project that will run a hydrogen fuel cell on biogas captured from dairy cows. It might seem that Haubenschild already made this point. For the last six years, Haubenschild Farms in Princeton, Minn., has run on electricity generated by the anaerobic digester he built with AgStar funds. He sold the excess—enough to power about 78 homes—to his electricity provider, East Central Energy. Great River Energy, ECE's generation and transmission provider, now buys Haubenschild's excess generation. New use for biogas To Haubenschild, generating his own electricity was only the beginning, however. His interest in tying hydrogen production to anaerobic digestion began almost as soon as he commissioned his biogas powerplant. "A solid-oxide fuel cell could produce enough heat to maintain the digester," he explained. "If the demonstration goes well, we might be able to scale up from the PEM (proton exchange membrane) cell we're working with now." Time and money constraints prevented the project from obtaining a more useful SOFC unit. However, the 5-kW, proton exchange membrane fuel cell provided by Plug Power, Inc. is the typical size for standard residential applications and good for research. It won't make much of a dent in Haubenschild's 60- to 80-kWh load, however, but that is not the point of the demonstration. The goal is to see if a fuel cell can make electricity from predigested, pre-collected biomass. "Fuel cells have generated electricity from methane, but this is the first time it's been done in an operation like this," said Dr. Philip Goodrich, the principal investigator on the project. Goodrich is an associate professor with University of Minnesota's Department of Biosystems and Agricultural Engineering, one of the sponsoring partners in the project. Other project partners include the Minnesota Department of Agriculture and the Minnesota Project. Great River Energy, Electric Power Research Institute, John Deere, Inc. and Plug Power are among the contributing partners. The Environmental and Natural Resources Trust Fund provided a $200,000 grant for the project through the Legislative Commission on Minnesota Resources. Clean gas means clean emissions U of M researchers have run fuel cells on biogas intermittently, but continuous biogas operation poses some challenges. The gas from the anaerobic digester is composed of methane, carbon dioxide, water vapor and caustic trace gases that can damage a fuel cell. "A PEM cell needs natural gas-quality or better fuel to operate efficiently," said Haubenschild. "A lot of the trial is experimenting with ways to clean the gas." A wastewater treatment plant in the state of Washington does clean up digester gas to pipeline quality, but a visit to the site convinced Goodrich that, "Just because one facility was doing it doesn't mean that it is going to work in different circumstances. They were able to recirculate the water used for scrubbing back into the treatment system," he said. "That option wasn't available to us." Goodrich developed a specialized water scrubber for the fuel cell, but it is not foolproof, he said. "We had to rebuild the system." Once the biogas is cleaned, it is converted to hydrogen fuel, which produces electricity in the fuel cell. The unit uses only two cubic feet of biogas per minute, compared to the 50 cfm Haubenschild's Caterpillar generator consumes. The fuel cell is much quieter than the internal combustion unit. "I wish we could put the sound of the engine on the Web site, so people could appreciate the difference," said Goodrich. Even more important, because the gas has been cleaned and the electricity comes from a chemical reaction instead of combustion, the water vapor exhaust contains near-zero emissions. A standard engine burning straight biogas emits 2,900 ppm NOx, 280 ppm SO 2 and 800 ppm CO. The fuel cell emissions contain less than 1 ppm of those gases. Head start on the future Those factors could help people accept electrical generators in their midst and get used to the idea of farmers supplying energy for their neighborhoods, Haubenschild believes. His vision doesn't stop with generating electricity, though. "I would like to produce hydrogen to run our tractors and to sell to cities for buses," he said. Researchers at U of M are working on technology that would allow hydrogen to be mixed with diesel, "Preferably biodiesel, to reduce emissions even more," Goodrich noted. Also, at this point, it is not clear that the fuel cell will produce more hydrogen than it needs to generate electricity. Goodrich hopes to find that out in the next two years. Even so, the idea of harvesting hydrogen fuel from biogas does not seem far-fetched to him. "Hydrogen may be one of the primary drivers of the economy within 10 years," Goodrich said. "Fuel cells and anaerobic digestion are part of this opportunity." In the meantime, the Haubenschild Farms digester will continue to deliver reduced odors and emissions, enhanced fertilizer for sale to local growers and, of course, clean electricity. If the fuel cell demonstration yields one more benefit of sustainable business, Dennis Haubenschild will not be surprised. "The by-product of animal agriculture is a non-depletable resource," he declared. "You have to think of it as product, not waste." |
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