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The Southeastern Regional
Sun Grant Center
2506 Jacob Drive
Knoxville, TN 37996-4570
Phone: (865) 946-1124
Fax: (865) 946-1109
Email: sungrant@tennessee.edu

Regional Competitive Grants

Project Title: Optimization of Pretreatments for the Production of Ethanol from Genetically Modified Hardwoods with High Cellulose and Low Lignin Content

Principal Investigators and affiliations:

  • PI: Hasan Jameel (North Carolina State University, Department of Wood and Paper Science)
  • Co-PI: Hou-Min Chang (North Carolina State University, Department of Wood and Paper Science)
  • Co-PI: Vincent Chiang (North Carolina State University, Department of Forestry)
  • Co-PI: Richard Phillips (North Carolina State University, Department of Wood and Paper Science)

Start Date: 9/1/2007      End Date: 8/31/2009

Project Abstract:

As the demand for ethanol increases it is critical that the resource base be broadened to include other sources of biomass. However, the intrinsic ligno-cellulosic characteristics in the natural populations remain as barriers to high conversion efficiency. These barriers include the amount and type of lignin and the accessibility of the enzymes to the carbohydrate matrix. One potential step towards producing ethanol from ligno-cellulosics is the development of transgenic trees with traits that facilitate the production of ethanol. Cellulosic biomass must be pretreated so that the matrix is expanded to allow for easier access to the cellulose. Pretreatment is among the most costly steps and as such has a significant impact on process design, efficiency of the bioconversion process and overall economics. Previous work has shown higher conversion efficiencies to sugars with transgenic hardwoods with low lignin and high cellulose. It is also expected that the pretreatment step can be simplified for these transgenic trees.
The proposed research will develop low cost pretreatments for transgenic hardwood trees with low/modified lignin and high cellulose. The impact of using simplified pretreatment strategies with genetically modified trees on the economics of ethanol production will also be evaluated. This proposal will address how new and improved feedstocks that have been modified using bio-engineering can simplify the processing steps in a biorefinery.

The objective of this research is to study different physical and chemical pretreatment technologies on the enzymatic hydrolysis efficiency of genetically modified hardwoods and to identify the most economical pretreatment. This study will focus on Populus, the one whose genome was recently sequenced. We already have transgenic Populus transgenics with a range of lignin reduction and with augmentation in lignin S/G ratio and cellulose content. It is expected that the pretreatment stage can be significantly simplified for trees with low lignin content. Physical pretreatments involving water and steam will allow for a simplified system with minimum requirements for chemical recovery. Chemical treatments of transgenic trees involving mild applications of alkali and oxidative chemicals will also be evaluated. These feedstock materials would also allow us to evaluate the effects of lignin quantity and structure in combination with various pretreatment options on the efficiency of ethanol production. This project will also evaluate the impact of these genetically modified trees on the economics of ethanol production especially with respect to simplifying the pretreatments necessary to make the substrate more amenable to enzymatic hydrolysis. The information from this research will be used in an economic and process model developed at North Carolina State University based on WinGEMS/EXCEL and using an ASPEN based model developed at NREL. The NC State model has already been used successfully to evaluate various biomass - based ethanol projects. This research is unique in that North Carolina State University is the only institution in the United States that has access to the transgenic trees and the expertise to carry out the different pretreatments and quantify their overall economic impact.

Two-year old transgenic trees (Populus) will be used to develop simplified pretreatments with respect to improved carbohydrate yield and enzymatic hydrolysis. An economic model developed at N.C. State University will be used to study the effect of the genetic modifications in combination with the simplified pretreatment strategies on overall ethanol production economics.

The following outcomes can be expected from this project for transgenic trees with low lignin/high cellulose, high reactivity lignin and a combination of both low lignin and high reactivity lignin:
•Development of the most cost effective technology for the pretreatment of the different transgenic trees
•An understanding of the differences in the chemical and physical properties of the fibers after pretreatment
•Quantification of the improvement in enzymatic hydrolysis that can be expected for the different pretreatments and the different transgenic trees
•An economic analysis of the impact of using wild versus transgenic trees on the design and operating cost of a wood to ethanol operation
•The EXCEL economic model of the overall process will be made available to evaluate the impact of raw material composition on ethanol production cost

Reports and Publications:

Quarter 1 - 2008
Quarter 2 - 2008
Quarter 3 - 2008
Quarter 4 - 2008

Quarter 1 - 2009
Quarter 2 - 2009