US can benefit from combining coal, biomass fuels

By Lisa Gibson
Liquid fuels from biomass and coal could reduce petroleum use and carbon dioxide emissions in the U.S. over the next 25 years, according to a recently released report, but producing the alternative fuels in an environmentally conscious way requires significant research, development and commercial demonstration.

"Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs and Environmental Impacts" looks at reducing the nation's dependence on foreign oil by transitioning to coal and biomass liquid fuels. The report, the first in a series for the National Academies' America's Energy Future project, discussed existing and future technologies, environmental impacts, associated costs and barriers to deployment. The report also estimated potential deployment on three timelines: less than 10 years, from 10 to 25 years and beyond 25 years.

"We suggest that the mixing of biomass and coal be explored," said David Tilman, professor at the University of Minnesota-St. Paul, and vice chair of the Panel on Alternative
Liquid Transportation Fuels. "It can actually be a carbon-neutral or carbon negative fuel."

The research team made three important findings: an adequate supply of biomass exists-an estimated 550 million tons annually by 2020-without running into direct and indirect land-usage issues; a mixture of coal and biomass, when gasified with carbon capture, is likely to provide more cost-efficient and greenhouse gas effective fuels; and maximizing carbon capture and sequestration is vital, according to Tilman. Geologic carbon storage is a high priority, he added, as it needs to be proven viable and safe on a commercial-scale before deployment of coal and biomass liquid fuels.

If the 550 million tons were combined with coal at a 60:40 coal-to-biomass energy ratio, 60 billion gallons of gasoline equivalent could be produced each year, about 45 percent of annual gas usage in the country, the report said. An estimated annual supply of 400 million tons of biomass could be produced sustainably with technologies and practices already available in 2008, the report adds.

But transforming the transportation system from petroleum-based fuels to various domestic sources will take several decades, the report says. In addition, it will be more than a decade before the alternative fuels reach full-market penetration.

Using biomass-specifically corn stover, wheat grass, switchgrass, native prairie plants, miscanthus and woody biomass-with coal unites the best of both worlds by providing the environmental benefits of biomass and the lower cost of coal, according to the report. Both are abundant in the U.S., making them excellent candidates for nonoil-based liquid fuels. The technology is not available in the U.S., but demonstration plants are in operation in Europe. Without storage of carbon dioxide, life-time greenhouse gas emissions from coal-based fuel are about twice that of oil, but with storage it could be about the same.

If safe and viable geologic carbon dioxide storage is developed at commercial-scale facilities by 2015, the first combination plants could be built in the U.S. by 2020, the report stated. By 2035, the country could produce 2.5 million barrels of gasoline equivalent per day, assuming a 20 percent growth rate in construction, it said.

The research team developed several recommendations from its findings involving collaboration among the U.S. departments of energy and agriculture, researchers and the biofuels industry to identify challenges, market penetration rates, carbon storage issues, conversion technologies, research and development needs, and spatial distribution of biomass in the country.

"The panel strongly felt that we should be trying to achieve a diversified portfolio of technologies," Tilman said. "If we're looking at how we can maximize fuel supply that is greenhouse gas friendly, an appropriate mixture [of biomass and coal] is probably the optimal mix for the country."