Modifying Lignin Structure in Poplar for Enhanced Biomass Conversion

For environmental and energy security purposes, the United States has established mandates for the production of cellulosic biofuels at a level of 100 million gallons in 2010, rising to 16 billion gallons by 2022. There has recently been significant interest in ensuring that the feedstocks for biofuel production be sustainable, and woody biomass has great potential to be. Forests have been shown to be renewable resources and tree plantations generally do not compete with food crops for land because of different growing conditions, thus sidestepping debate about alternative uses of crop land. There already exists a well established forestry industry and the first modern pilot-scale cellulosic ethanol plant utilizing woody biomass is expected to begin operation in 2010. It is estimated that woody biomass could produce 368 million tons per year with existing land resources, representing more than 30 billion gallons of ethanol production. One of the more promising trees for biofuel use is hybrid poplar. Hybrid poplar is well known for rapid growth and its ability to produce large quantities of biomass, as some varieties of poplar grow eight feet per year. While poplar plantations can be harvested for pulp after ten years? growth, they can be sustainably harvested for biomass after just six years in optimal climates such as the Pacific Northwest, and after eight years in most other regions in the U.S. Short-rotation intensive culture (SRIC) methods are under development for biomass production, involving coppicing of the plantation at the end of the first year of growth and harvesting the biomass in three-year rotations. However, there are still significant challenges to producing cellulosic biofuel from woody biomass economically due to the difficulty of deconstructing the cellulose in the plant cell wall, with the cross-linked lignin in the cell wall being the primary challenge. The project will address that challenge by developing enhanced poplar varieties with modified lignin that can be more readily broken down during processing. The use of this biomass feedstock will reduce the energy needs and costs associated with the production of cellulosic biofuels and other renewable chemicals.