Whatcom County’s 55,000 dairy cows produce nearly 60 tons of manure each day. But with the help of newly-developed technology to generate electricity and fuel vehicles, dairies are putting that waste to work by helping to decrease methane emissions and dependency on fossil fuels. The daily manure from eight cows can power an average home for one day, said Kyle Juergens, assistant manager of the digester project at the Vander Haak dairy in Whatcom County.
Western Washington University students at the Vehicle Research Institute are building a purification system called a “bio-methane gas scrubber” that would refine biogas, a mix of bio-methane, carbon dioxide and traces of hydrogen sulfide. After biogas is “scrubbed” the result is pure bio-methane, to be used as a vehicle fuel. The biogas would supplement the current supply of natural gas and provide a better means of using renewable resources.
Methane Basics
Methane is a greenhouse gas that traps heat in the atmosphere and contributes to global warming. Methane, or natural gas, remains in the atmosphere for approximately nine to 15 years and traps heat 20 times more effectivly than carbon dioxide, according to the Environmental Protection Agency.However, methane can generate electricity, heat homes and power automobiles. Additionally, methane already has an infrastructure in place for distribution to most homes throughout the United States.
Natural gas companies drill and place wells in the ground for the extraction of methane, which forms during the decay of ancient forests and sea life trapped in the ground for millions of years. The drilled gas is approximately 90 percent methane and 10 percent carbon dioxide. Gas companies rid the gas of carbon dioxide to make it “pipeline quality.”
The digester’s methane product, however, faces a problem that drilled methane does not have — the methane produced from manure has approximately 40 percent carbon dioxide and trace amounts of hydrogen sulfide, Juergens said. Even in trace amounts, hydrogen sulfide corrodes key engine components vital to internal combustion, he said.
Bio-methane scrubber technology cleans the gas to eliminate carbon dioxide and hydrogen sulfide.
Sweden uses scrubber technology and has an entire public transit system built around natural gas, according to U.S. Department of Energy reports. However, high maintenance costs have discouraged their use in the United States.
Juergens said the available gas scrubbers need regular filter replacement, which makes them too expensive to maintain and less economical than frequent oil changes. The VRI design is a more economical approach to purifying bio-methane, he said.
The VRI Scrubber
Another problem with the methane produced by digesters, said Eric Leonhardt, director of the VRI, is that the impurities make the gas difficult to compress efficiently for storage and transportation. But once the gas passes through the scrubber, the compressed biogas can be used in natural gas vehicles and will not corrode engine parts, Leonhardt said.
“The scrubber is really a small refinery for bio-methane,” Leonhardt said.
The VRI’s scrubber is a foot-and-a-half in diameter, 6-foot-tall tube. An irrigation sprinkler at the top sprays a hydrogen sulfide and water solution. Small objects, called bio-balls that are covered with tiny, plastic spines that increase their surface area, fill the tube. A line pumps in the biogas at the bottom end.
First, the sprinkler sprays down the solution and coats the bio-balls. Then, biogas slowly travels up through the coated bio-balls. The solution attracts the impurities and a clean, refined bio-methane gas collects at the top of the tube. The bio-balls and solution act as a filter, which do not require costly replacement like other scrubber technologies, Leonhardt said.
The purified gas is easily compressible and the VRI will use it in Viking 32, a compressed natural gas-electric hybrid, he said.
No one else is producing a compressed natural hybrid powered by bio-methane, which makes Viking 32 a “one-of-a-kind car,” said Ryan Cruse, a Western environmental policy and vehicle design student and member of the Viking 32 Hybrid Team.
A Honda Civic natural gas engine powers Viking 32’s rear wheels and a Unique Mobility electric motor drives the front wheels, Cruse said.
“We are taking hybrid propulsion systems and taking it one step further,” he said.
Leonhardt said retrofitting a gasoline engine to run on bio-methane natural gas is possible, but expensive.
“You would have to change out expensive internal components,” Leonhardt said.
BAF Technologies is the leader in natural gas and propane vehicle retrofits across the United States, according to the EPA. The company converts Ford and GM vehicles into natural gas or propane-burning vehicles for company fleets and state and federal agencies. But according to the company’s Web site, few private citizens retrofit their gas engines because of the enormous expense.
VRI Lab Manager, Ian Bissell said while up-front costs may be high for the natural gas conversion, the savings are long-term with decreased operating and fuel costs.
Bissell said if the scrubber can cheaply purify biogas from dairies, then other dairies would have an incentive to invest in scrubber technology. They could then sell bio-methane to natural gas companies. The gas companies could then use a renewable resource instead of finite, drilled methane, Bissell said.
The current price of gasoline has consumers feeling the pinch at the pump. According to the U.S. Department of Energy, crude oil prices reached an all-time high during the third week of April 2006, at $75 a barrel. In 1998 the price was $14 a barrel, adjusted for inflation.
Cheap fuel supplies such as biogas could also shift public opinion toward natural gas vehicles and persuade automakers to invest in expanded natural gas vehicle programs, Bissell said.
“When supplies go up, prices go down,” he said. “And with gasoline so expensive, natural gas could emerge as the dark horse of the alternative fuels war.”
Cruse said as cleaning bio-methane and using it as a vehicle fuel becomes more economically feasible, current practices of igniting excess gas so it does not escape into the atmosphere, will be replaced by scrubbing facilities that clean and sell the gas.
Western’s VRI is funding all of their natural gas projects, but has applied for a grant from the EPA to help fund the scrubber project. Paccar, a local automotive design and manufacturing firm, has donated gas tanks for the institute’s natural gas projects, and a local dairy provides the biogas.
The VRI holds no patents on the project, and Leonhardt said neither he nor the VRI expect to see any income as a result of their research. He said the project’s main goal is to build vehicles powered by a more sustainable fuel source.
According to the EPA, methane emissions since 1990 have been consistently lower than projections because of “voluntary action programs,” like the anaerobic digesters and natural gas vehicles. Still, millions of cubic feet of methane escape into the atmosphere every year and contribute to global warming. Technology such as the VRI’s scrubber may be a vehicle of change that promotes a better environment for future generations.