life habitat; and rural development in a comprehensive manner. Such incentives might encourage farmers, foresters, biomass aggregators, and biorefinery operators to work together to enhance technology development and ensure that best management practices were used for every combination of landscape and potential feedstock.

An estimated annual supply of 400 million dry tons of cellulosic biomass could be produced sustainably with technologies and management practices already available in 2008. The amount of biomass deliverable to conversion facilities could probably be increased to about 550 million dry tons by 2020. The committee judges that this quantity of biomass can be produced from dedicated energy crops, agricultural and forestry residues, and municipal solid wastes with minimal effects on U.S. food, feed, and fiber production and minimal adverse environmental effects.

Biomass availability could limit the size of a conversion facility and thereby influence the cost of fuel products from any facility that uses biomass irrespective of the conversion approach. Biomass is bulky and difficult to transport. The density of biomass growth will vary considerably from region to region in the United States, and the biomass supply available within 40 miles of a conversion plant will vary from less than 1,000 tons per day to 10,000 tons per day. Longer transportation distances could increase supply but would increase transportation costs and could magnify other logistical issues. The development of technologies that increase the density of biomass in the field, such as field-scale pyrolysis, could facilitate transportation of biomass to larger-scale regional conversion facilities.

Improvements in agricultural practices and in plant species and cultivars will be required to increase the sustainable production of cellulosic biomass and to achieve the full potential of biomass-based fuels. A sustained research and development (R&D) effort to increase productivity, improve stress tolerance, manage diseases and weeds, and improve the efficiency of nutrient use will help to improve biomass yields. Focused R&D programs supported by the federal government could provide the technical bases for improving agricultural practices and biomass growth to achieve the desired increase in sustainable production of cellulosic biomass. Attention could be directed toward plant breeding, agronomy, ecology, weed