Background

1. Comparison of Fuel Cell and a Genset Utilizing BiogasPhilip R. Goodrich PE*, David Nelson PE*, Richard Huelskamp*, Dennis Haubenschild**, Matthew Drewitz***, Paul Burns***, David Schmidt PE*, R. Vance Morey** Department of Biosystems and Agricultural Engineering, U of Minnesota,** Haubenschild Farms, Princeton MN***Minnesota Department of Agriculture 1Other participants in this project include: Amanda Bilik, The Minnesota Project, Verlyn Johnson, Blanca Martinez, BAE and Henry Fischer, East Central Energy. Background Plug-Flow Digester - A small “plug” of slurry is pumped into one end each day, causing a comparable amount to flow out of the other end into the storage basin in the background. The Haubenschild Farms Digester and Energy Recovery System Anaerobic digestion converts volatile organic substances in livestock wastes into methane, carbon dioxide, gaseous contaminants and water vapor. The remaining material is stabilized, reducing odor during storage and land application operations. The energy in the methane can be converted into electrical energy in various ways. The most popular method is an internal combustion engine coupled to an alternating current induction generator connected to the grid. A fuel cell is a newer way to convert the methane into electrical energy which is more challenging Dennis Haubenschild is an early adopter of anaerobic digestion using AGSTAR (US Environmental Protection Agency) resources to install one at Haubenschild Farms, an 800-cow, 1000-acre dairy farm an hour north of Minneapolis/St. Paul MN. In 1999, the farm installed a heated plug-flow digester with a 135-kilowatt engine/generator to utilize the biogas. The successful operation of this facility (the generator has been running over 98% of the time through July 2004) has drawn many visitors and helped other operations to accept the technology. Biogas Production used in Generator The building at the left houses the 135 kW engine generator and the building on the right houses the fuel cell and instrumentation. One barn is to the right rear of the picture SOURCE: Nelson and Lamb Objective To demonstrate the feasibility of converting biogas methane to electrical energy using a commercially available fuel cell. Comparing Electrical Generator Technologies Challenges to using biogas for a fuel cell • Hydrogen sulfide removal • Initial concentration 3000-5000 ppm • Need concentration < 25 ppb • Moisture removal • Need dry gas • Dewpoint < -30 degrees Celsius • Carbon dioxide removal • Need concentration < 5 ppm Fuel Cell System • Cost per kilowatt is very high. $10,000 -->20,000 per kW • The biogas must be cleaned up to strict specifications. Adds cost and complexity while consuming energy. • The fuel cell is an emerging technology. • The greenhouse emissions and particulates are very low. • The system is very quiet. • There are few moving parts. • Cost of maintenance is not yet known. • The fuel cell technology is continuously improving at a rapid rate. • Engine Generator System • Cost per kilowatt is low. $50 -->100 per kW • The biogas can be used directly from the digester with no cleanup. • The fuel cell is mature technology. • The greenhouse emissions of carbon dioxide, sulfur dioxide carbon monoxide and particulates are significant. • The noise level is very high and sound mitigation is necessary. • There are many moving parts, most moving in a hot environment needing oil and cooling • The technology is mature and changing slowly. Emissions from Haubenschild Generator Compared to Plug Power™ Proton Exchange Membrane (PEM) Fuel Cell Engine Generator Emissions** 1.89 % O2 0.0796 % CO ( 796ppm) 0.187 % NOx (1872 ppm) 0.0804 % SOX (804 ppm) 1.39 % CX HY **Actual tests on Haubenschild Farm Dec 2004 Fuel Cell Emissions* 79 % O2 and N2 15.5 % H2O 4.2% Co2 <.001% Other Other = propane,NOx,SOx,CO *Per Plug Power tests Advancing Utilization of Manure Methane Digester Funding for this project was recommended by the Legislative Commission on Minnesota Resources from the Minnesota Environment and Natural Resources Trust Fund