Comparison of Fuel Cell and a Genset Utilizing Biogas
Philip 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
participants in this project include: Amanda Bilik, The Minnesota Project, Verlyn Johnson, Blanca Martinez, BAE and Henry Fischer, East Central Energy.
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. The Haubenschild Farms Digester and Energy Recovery System
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.
Biogas Production used in Generator
Biogas Produced (ft3/day)
80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 09/17/99 09/16/00 09/16/01 09/17/02 09/17/03 09/17/04
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
To demonstrate the feasibility of converting biogas methane to electrical energy using a commercially available fuel cell.
Comparing Electrical Generator Technologies
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.
Challenges to using biogas for a fuel cell
Hydrogen sulfide removal
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
Initial concentration 3000-5000 ppm Need concentration < 25 ppb
Need dry gas Dewpoint < -30 degrees Celsius
Carbon dioxide removal
Need concentration < 5 ppm
• There are few moving parts.
• Cost of maintenance is not yet known. • The fuel cell technology is continuously improving at a rapid rate.
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
•The technology is mature and changing slowly.
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