If a bioenergy or biobased industry is to be truly successful, sustainable, and economically competitive with fossil fuels, the biomass resource must meet a number of conditions:
Woody Biomass, both rural and urban, is one of few biomass feedstocks that can satisfy each of these prerequisites. Forests and woodlands in the contiguous United States can produce nearly 370 million dry tons annually from harvest residues, fuel treatments, small diameter trees, urban wood waste, and mill residues (Perlack et al, 2005). Nationally, approximately 40 million dry tons of collectable logging residues are unused each year (Gan and Smith 2006).
In addition, millions of tons of woody biomass are also made available from insect, disease, and extreme weather conditions each year. For example, 800 million dry tons of wood were destroyed just by hurricanes in 2005 (USDA Forest Service 2005) (Texas Forest Service 2005). All of these forest resources (except for mill residues) are not currently utilized, do not significantly compete with other uses, and are available on a sustainable, environmentally sound basis. If we assume ethanol (or similar fuel) yields of 100 gallons per dry ton (with advanced technology), then 370 million dry tons is equivalent to 37 billion gallons of ethanol, gasoline, and gasoline additive annually or 25% of annual U.S. motor gasoline consumption (approximately 150 billion gallons).
A very important aspect for consideration is the fact that these resources are currently burned, left in the field to decay, or sent to landfills. Using this woody biomass from the source listed above could actually significantly alleviate (not add to) environmental and economic pressures. Utilization of woody biomass for bioenergy, for example, can help mitigate greenhouse gases because of its carbon-neutral attribute; contribute to the development of healthier forests particularly when pre-commercial thinning is applied; significantly reduce or eliminate loss from catastrophic wildfires, insects and disease and the concomitant degradation to watersheds; reduce GHG emissions, help control invasive species, bolster rural economies, and reduce the nation’s dependency on foreign oil (Foster et al. 2007).
The only major hurdle for woody biomass utilization has been the development of technology that could cost-effectively process woody biomass and other lignocellulosic biomass into biofuels and high value biobased products with special considerations for transportation and storage cost of the raw material. Lignocellulosic materials are essentially long, molecular chains of sugars protected by lignin. Since this lignin bond has been difficult to cost-effectively remove, the technological hurdle for using these materials has been to: (1) discover a process that will efficiently separate lignin from the cellulose and hemicellulose; (2) build the process into an integrated biorefining unit; and (3) overcome feedstock limitations in order to make the system cost competitive with fossil fuels.
The benefits of utilizing woody biomass for bio-based products are many. These benefits are environmental, economic, social, and energy related. The use of woody biomass for bioenergy can help mitigate greenhouse gases (woody biomass utilization would displace about 19.4 million tons of carbon annually), contribute to the development of healthier forests, bolster rural economies, and reduce the nation’s dependency on foreign oil.
Roundwood Image by EL Taylor