Regional Competitive Grants

Start Date: 9/15/2007      End Date: 8/14/2010

Project Abstract

The technological and economical feasibility of processing agricultural residues using twin screw extrusion technology to dissolve and saccharify the biomass to energy related byproducts in an integrated single process will be demonstrated. The agricultural residues considered are bagasse (the cellulosic residue from sugar cane processing) and filter cake, draff (particularly the residue from grain processed for alcoholic spirits), wood wastes, and biomass residue from food processing. The mono-, di-, and oligosaccharides intermediate products could form the feedstock for a biorefinery or with subsequent step(s) to directly produce energy sources such as ethanol, hydrogen, and butanol. Three major foci of this proposal are: 1) residual biomass accumulated in a central source for production of a primary product(s); 2) use of enzymatic pathways and/or hot compressed water for conversion of the lignocellulosic biomass for lower process energy consumption. 3) use of ionic liquids and a similar solvent, N-methyl morpholine oxide monohydrate (NMMO•H2O) i.e. the lyocell solvent, in multiphase systems to dissolve the lignocellulosic biomass for significantly enhanced enzymatic reactions in the solution rather than the solid phase. The first focus will mitigate the economic disadvantage of processing and transporting low bulk density biomass to a central facility for conversion. The second and third foci will significantly reduce the process energy required for conversion and significantly enhance the reaction rates by having the biomass and reactants in well dispersed solution phases rather than in a solid phase. Hydrothermal saccharification in the twin screw extruder will also be included as an alternate approach and as a bench mark for the enzymatic saccharification. The process economics and conceptual life cycle for the processes are integral to the proposal, therefore the total energy consumption and environmental affects will be considered.

Cellulosic biomass will be saccharified to mono-, di-, and oligosaccharides by continuous processing in a twin screw extruder. Process economics will be enhanced by combining process steps into one continuous operation. The biomass will be dissolved in environmentally friendly solvents for rapid enzymatic reaction. The two environmentally friendly solvents will be NMMO•H2O and [C4mim]Cl. Since a common cellulase (Trichoderma reesei) is deactivated in [C4mim]Cl and probably in other ionic liquids, the NMMO•H2O will be considered for use with Trichoderma reesei first for processing. Simultaneously other cellulases will be tested for activity in [C4mim]Cl and possibly other ionic liquids. Concurrent development of using a twin screw extruder as a HCW and comparative process economics and conceptual life cycle analysis of HCW and enzymatic systems will be conducted. These reactions will be conduced in a twin screw extruders that are noted for their capability to be configured to perform multiple processes including chemical reactions, in a single operation. They are used for the reactive polymerization of polyamides and polyesters on a commercial scale and are used in the food processing industry. Twin screw extruders typically are easily reconfigured by pulling the screws and rearranging the interchangeable elements. As a result mixing sections can be placed at specific location down the barrel to accomplish dissolution of the cellulose and other biomass, and also to accomplish excellent contact between distributed phases of a multiphasic system. They can be equipped with multiple feed, injection and product removal section. The twin screw extruders can be configured to have the biomass and solvent input through the initial feed port, then the biomass dissolved, injection of the enzyme further downstream in a separate phase, followed by a reaction section, and volatile materials can be removed at different sections including near the discharge end of the extruder.

This proposal is directed at employing existing technology from related fields to enhance the economics and viability of converting lignocellulosics to at least intermediate products that can become energy sources and the feed stock for biorefineries. Twin screw reactive extrusion that will employed has been developed to combine multiple processing steps into a single operation for plastics and food processing and will be employed in this project. Dissolution of the lignocellulosics in either of two environmentally friendly solvents, N-methyl morpholine oxide/water or and the ionic liquid 1-butyl-3-methylimidazolium chloride will significantly enhance the reaction rate and yield since the lignocellulosics will be in solution. Other processes are limited by reactions with lignocellulosics in the solid and less accessible stage. Enzymatic processing will lessen the energy consumption of the processes. Furthermore, multi phase processing will minimize the effects of the solvent on the enzymes that will be present in a separate phase. Hot compressed water in the twin screw reactive extruder will also be included to provide a benchmark and also an alternate process. By concentrating on residual biomass accumulated at a central source to produce a different primary product the cost of transporting low bulk density biomass to a central facility for processing is minimized.
Process economic and conceptual life cycle analysis will be preformed on the candidate processes.

As a result of this research the basis of an economical process for the saccharification of lignocellulosics residual biomass will be demonstrated. The relative technological and process advantages of the processes considered will be elucidated. If the resultant process involves solution processing, then an appropriate candidate solvent and enzyme combination will have been identified. Appropriate condition will be identified for the candidate processes. The value of integrating several steps into one process using twin screw reactive extrusion and on the use of residual biomass accumulated at a central source for processing a different principle product will be demonstrated. If new enzymes are identified this research will demonstrate their potential application and both enzyme and process requirements.

Reports and Publications:

Quarter 1 - 2008
Quarter 2 - 2008

Quarter 1 - 2009
Quarter 2 - 2009