U.S. Forest Service: ethanol from forests can replace 15 percent of gasoline

The U.S. Forest Service chief Abigail Kimbell is proposing replacing 15 percent of the United States' gasoline with ethanol made from wood obtained from thinning unhealthy forests, while doubling the amount of carbon dioxide emissions absorbed by public and private forests.

Kimbell presented the proposal in a speech before the Society of Environmental Journalists in San Francisco. These are ambitious goals, and they would take a concerted national effort to reach.

New biofuel technologies
According to Kimbell, with the technologies now becoming available, the U.S. could replace as much as 15 percent of its current gasoline consumption with ethanol from wood — and not just any wood, but 'unhealthy' wood that is not being used for other purposes and that must be removed from forests to prevent wildfires. Second-generation biofuel technologies capable of converting this type of woody biomass consist of biochemical and thermochemical conversion techniques.

Of these technologies, the thermochemical pathway known as pyrolysis is most advanced and cost-effective. But biochemical conversion techniques, based on enzymes that succeed in breaking down lignocellulosic biomass, are receiving a great deal of research and investment. Alternative routes consist of gasifying wood and converting the syngas via Fischer-Tropsch synthesis into ultra-clean synthetic biofuels.

The wood for ethanol would come mainly from undergrowth that the 'healthy forests' law now requires to be removed to prevent wildfires. The Healthy Forests Initiative contains a variety of provisions to speed up such hazardous-fuel reduction and forest-restoration projects on specific types of Federal land that are at risk of wildland fire and of insect and disease epidemics.

A lot of our forests across our country are unhealthy because they're overstocked. There's a lot of unhealthy underbrush. That's where we're talking about getting the bioenergy from. It's from the reduction of flammable fuels in the forests — instead of just burning it up in piles or grinding it up. - Allison Stewart, spokeswoman U.S. Forest Service

Besides use for the production of liquid fuels, small-diameter trees and underbrush can also be used as solid biofuels to heat homes and to generate renewable electricity.

Questions
The biofuel plan is ambitious and it is not clear how the biomass logistics would work out. Thinning forests and removing underbrush is labor intensive and transporting this low energy density biomass to central biofuel facilities would probably be uneconomic.

However, several innovations have seen the light that allow for a decentralised production system. New forest residue harvesters integrated with wood chippers have been developed (earlier post), as have mobile pellet plants. Small, modular pyrolysis plants can be located close to the source of the biomass (more here). There, the wood would be transformed into bio-oil with a higher energy density. This oil can then be transported more efficiently to a central biorefinery that refines the pyrolysis oil into specific fuels ready for use in cars:
energy :: sustainability :: ethanol :: synthetic biofuels :: pyrolysis :: Fischer-Tropsch :: forestry :: wildfire :: biomass ::

The Forest Service estimates that America's forests — both public and private — offset about 10 percent of carbon emissions in the United States. Kimbell proposes a national effort to double that amount by 2020. The Forest Service manages 155 national forests and 20 national grasslands — an area equivalent to the size of Texas.

While producing biofuels, the Forest Service will at the same time be "doing a lot of replanting of new forests, where there are no forests now." Most of those are in areas cleared out by wildfires, floods and other calamities of nature.

Trees absorb carbon dioxide, but the science for measuring how much is unsettled. Some have suggested forests in temperate climates contribute to climate change, whereas grasslands would do more to reduce global warming.

Despite these uncertainties, the Forest Service is teaming up with the nonprofit National Forest Foundation to allow consumers to participate in a voluntary program to "offset" their carbon dioxide emissions by making charitable contributions that will be used to plant trees and do other work to improve national forests. Several such reforestation projects have been identified in the Custer National Forest in Montana and South Dakota and in the Payette National Forest in Idaho.

Picture: Fire Behavior in a small area that was thinned: fire burns low and on the ground. The U.S. Forest Service now proposes to utilize the removed underbrush and thinnings for the production of biofuels.

References:
Associated Press: Forest Chief Touts Ethanol to Power Cars - September 8, 2007.

KSBY: Forest Service chief urges using forests to power cars on ethanol - September 8, 2007.

Forests and Rangelands, official site of the U.S. Healthy Forests Initiative.

Biopact: Efficient timber harvester delivers wood chips on the spot, improves biomass logistics - August 19, 2007

Biopact: The mobile pellet plant - April 29, 2007

Biopact: Dynamotive begins construction of modular fast-pyrolysis plant in Ontario - December 19, 2006