Pretreatment of Agricultural Residues Using Aqueous Ammonia for Fractionation and High Yield SaccharificationEPA Grant Number: R831645
Title: Pretreatment of Agricultural Residues Using Aqueous Ammonia for Fractionation and High Yield Saccharification
Investigators: Lee, Y. , Elander, Richard
Institution: Auburn University Main Campus , National Renewable Energy Laboratory
EPA Project Officer: Richards, April
Project Period: June 1, 2004 through May 31, 2006 (Extended to December 31, 2006)
Project Amount: $190,156
RFA: Technology for a Sustainable Environment (2003) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , Sustainability
The objective of this project is to develop a pretreatment process suitable for enzymatic conversion of agricultural residues into fermentable sugars. The proposed process uses aqueous ammonia (a non-polluting substance) as the pretreatment. Use of ammonia offers significant economic and environmental merits since it is easily recycled and leaves no residual effect on the environment. The proposed pretreatment is a part of the integral biomass-to-fuels process that does not generate net CO2 (a green energy process). It is a pretreatment method of our own invention. When it is incorporated into the current biomass saccharification processes, it can accomplish a near complete fractionation of biomass into the three major constituents (pentosans, cellulose, and lignin). We intend to expand the fundamental knowledge base of this method and advance it to a point where it can be evaluated as a process technology.
A pretreatment process is applied before the biomass is subjected to the biological processing. The proposed method has been proven to be highly effective in delignification of agricultural residues and herbaceous feedstocks. Delignifying biomass at the early phase of the process is beneficial for a number of reasons. Low lignin in the solid substrate improves the digestibility and the overall enzyme efficiency thus lowering the enzyme dosage. The low-lignin carbohydrates are less toxic to microorganisms. Early removal of lignin also eliminates the complications in the down-stream processing including the cell separation in the bioreactor and the distillation. The lignin separated by the proposed process is clean and free of contaminants. It is a high-grade fuel with no known environmental problems. It is also a potential feedstock very much amenable for further conversion into value-added chemicals. In addition to the clean lignin, the proposed process can produce high-grade cellulosic material that has broader market than the saccharification feedstock. It is a short chain cellulose fiber with high -glucan content. Its potential market includes filler-fiber in papermaking and microcrystalline cellulose. The technical elements in this project are:
1. Laboratory investigation to refine and optimize the operating conditions of the proposed process using selected biomass feedstocks, primarily corn stover.
2. Evaluation of the treated feedstock in terms of the enzymatic digestibility based on cellulase enzyme and the ultimate ethanol yield by Simultaneous Saccharification and Fermentation (SSF).
3. Development of a proof-of-concept laboratory continuous co-current reactor for the proposed pretreatment.
4. Characterization and evaluation of the low-lignin end product as a filler-fiber in papermaking.
5. Sensitivity analysis of the process conditions and overall economic analysis of the proposed process.
The proposed research will develop a pretreatment process based on aqueous ammonia and test it against agricultural residues including corn stover. The proposed pretreatment method aims to fractionate the biomass into the three major constituents. The end products of this pretreatment are to be evaluated as feedstock for enzymatic saccharification and as low-lignin fibers. A laboratory scale continuous (or semi-continuous) pretreatment reactor will be developed and the design and operational data base will be established.