Transcript Biogas Production Economics: A Minnesota Case Study

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
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
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
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.
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
Biogas Produced
(ft3/day)
90,000
80,000
70,000
60,000
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
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
Date
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
Fuel Cell System
Engine Generator System
• Cost per kilowatt is very high.
$10,000 -->20,000 per kW
•Cost per kilowatt is low.
$50 -->100 per kW
• The biogas must be cleaned up to strict
specifications. Adds cost and
complexity while consuming energy.
•The biogas can be used directly from the
digester with no cleanup.
•The fuel cell is mature technology.
• The fuel cell is an emerging
technology.
• The greenhouse emissions and
particulates are very low.
• The system is very quiet.
•The greenhouse emissions of carbon
dioxide, sulfur dioxide carbon monoxide
and particulates are significant.
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
•The noise level is very high and sound
mitigation is necessary.
• Cost of maintenance is not yet known.
•There are many moving parts, most
moving in a hot environment needing oil
and cooling
• The fuel cell technology is continuously
improving at a rapid rate.
•The technology is mature and changing
slowly.
• There are few moving parts.
Challenges to using biogas for a fuel cell
Emissions from Haubenschild Generator Compared to Plug Power™
Proton Exchange Membrane (PEM) Fuel Cell
Engine Generator Emissions**
Fuel Cell Emissions*
1.89 % O2
0.0796 % CO ( 796ppm)
0.187 % NOx (1872 ppm)
0.0804 % SOX (804 ppm)
1.39 % CX HY
79 % O2 and N2
15.5 % H2O
4.2% Co2
<.001% Other
Other = propane,NOx,SOx,CO
**Actual tests on Haubenschild Farm Dec 2004
*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