SBIR-STTR Award

Woody biomass is a very important feedstock for the future bioeconomy for the rural US for its availability in large quantities, ease in storage, and low cost for transportation. However, woody biomass, especially softwood, is the most difficult to convert biochemically to fermentable sugars due to its strong physical integrity and chemical recalcitrance. The goal of this project is to develop a commercially deployable technology for woody biomass bioconversion to produce ethanol or specialty chemicals. The proposed technology, SPORL, showed superior performance in preliminary laboratory study to achieve over ninty percent softwood cellulose conversion to glucose in forty hours with normal enzyme dosage even when pretreatment is directly applied to wood chips without size reduction. The SPORL process can utilize existing technologies in the pulp and paper industry for commercialization, therefore it has low technological and environmental risks. With the continued decline of the US pulp and paper industry and shutting down many pulp and paper mills, many highly paid manufacturing jobs in rural US have being lost, which caused severe economic hardship and stress for rural US. The proposed technology can provide unlimited opportunities for those displaced people in rural pulp and paper mill towns to move into the biotechnology industry with a bright future. Furthermore, the proposed technology provides a viable avenue for value added utilization of underutilized forests and related resources, such as those from thinning of overpopulated forests. These underutilized forest resources have become a hazard and caused many catastrophic fires that have severely threatened the health of forest land and ecosystems in the last a couple of decades. OBJECTIVES: The overall objective of this proposed research is to develop a commercially deployable platform based on SPORL for biochemical conversion of woody biomass to biofuel. The success will be measured by the adoption of this platform for large scale demonstration by industry in 3-5 years after the phase II of this research. Many aspects of the SPORL process still remain unknown such as mass balance, optimal process conditions, high consistency saccharification, and fermentability of sugar streams; await investigation through this proposed research because the process was just recently invented. Therefore, for the selected woody biomass feedstocks the specific objectives are to conduct complete mass balance to understand the effects of pretreatment conditions on the formation of fermentation inhibitors, cellulose conversion efficiencies, and recovery of monomeric and oligomeric hemicellulose sugars. Optimization of SPORL pretreatment conditions, including the potential of using steaming SPORL chemical impregnated wood chips, based on enzymatic hydrolysis yield and hemicellulose sugar recovery from pretreatment spent liquor or hydrolysate. Next is optimization of mechanical refining conditions based on achieving minimal size reduction energy consumption for fiberizing SPORL pretreated wood chips and high cellulose conversion to glucose. Next is to conduct high consistency enzymatic saccharification and fermentation to understand the effect substrate size and consistency on liquefaction, cellulose conversion, and ethanol yield. Finally is to optimize ethanol yield from fermenting hemicellulose sugars from pretreatment. APPROACH: The work plan include laboratory pretreatment optimization and optimization of size-reduction, enzymatic saccharification and fermentation. There will be four tasks to address the specific objectives for the project. To fit the mission of the Research Topic of Forests and Related Resources, we will use lodgepole pines from thinning operations in the National Forests. The wood chips will be produced using a laboratory chipper at the Forest Products Laboratory. The chips will be screened and frozen. For each type of wood feedstock, wood chips, Surface Response Methodology will be used to design an experimental matrix to optimize process variables of SPORL: pretreatment temperature, duration time, pretreatment liquor to wood ratio, sulfite dosage, and sulfuric acid dosage or pH. Surface response design requires less numbers of experiments than factorial design while maintains integrity of experimental optimization. For optimization studies, SPORL pretreatment will be carried out in bomb type digesters of 100 gram capacity in an autoclave configuration. After the SPORL pretreatment, the pretreatment spent liquor or hydrolysate that contains hemicellulose sugars will be collected. The samples will then be mechanically run through size-reduction and substrate size characterization. The hydrolysates will then be run through enzymatic saccharification and fermentation. Finally, a complete chemical composition analysis of the feedstock wood chips, substrates, and hydrolysates or pretreatment spent liquors will be carried out using an improved high-performance anion exchange chromatographic method with pulsed amperometric detection

The SPORL process consists of reacting wood chips with a solution of calcium, magnesium, or sulfite at elevated temperatures for a short time, and then size reducing the resulting material using a disk refiner to generate fibrous substrate for subsequent saccharification and fermentation. The work is a collaborative effort between industry, university, and federal agencies. Forest biomass is a very important feedstock for the future bioeconomy for the rural United States because of its availability in large quantities, flexible harvesting schedule that eases storage, and low cost for transportation due to high density and low ash content. About 30 percent of the projected annual sustainable available biomass is forest biomass based on the billion ton study. To meet local rural United States bioenergy needs and promote biodiversity, forest biomass will be an important integral part of the biomass feedstock supply. However, forest biomass, especially softwood, is very difficult to convert biochemically to fermentable sugars for cellulosic ethanol or biofuel production due to its strong physical integrity and chemical recalcitrance. The goal of this project in Phase II is to prove this commercially deployable technology for forest biomass bioconversion to produce cellulosic ethanol and lignin bioproducts at the pilot scale. The research proposed will create an opportunity for rural economic development through sustainable green energy production. While the commercial production of cellulosic ethanol is nonexistent currently in the United States, it expected that about 500 biorefineries will be built in the next 15 years to meet goal of 16 billion gallons of cellulosic ethanol set by the advanced fuel standard in the EISA of 2007. The development of this future biorefining industry will take place primarily in the rural areas where large quantities of biomass feedstock are available at a low cost. Producing ethanol from cellulose promises to greatly increase the volume of fuel ethanol that can be produced in the United States. That will not only benefit the United States, but could help poorer nations by reducing fuel cost. With the ever increasing occurrence and intensity of forest fires, large volume and high value utilization of forest thinning materials is critical to mitigate the very expensive cost for forest thinning operations to reduce fuel loadings. The woody biomass form forest thinnings meet the advanced fuel standard. The SPORL technology provides a viable avenue for utilization of the thinning materials, which makes thinning and healthy forest management operation sustainable. This will enhance our biofuel resource base by providing new feedstock. Therefore, the proposed research has the potential to enhance international competitiveness of American agriculture, enhance the competitiveness and sustainability of rural and farm economics, support increased economic opportunities and improved quality of life in rural America, and protect and enhance the Nation's natural resources base and environment. OBJECTIVES: The overall objective of this project is to develop a commercially deployable platform based on SPORL for biochemical conversion of woody biomass to biofuel. We have developed a novel sulfite pretreatment process (SPORL) for robust conversion of woody biomass to fermentable sugars through enzymatic hydrolysis for bioethanol production, patent pending. The pretreatment is mild and the resulting wood chips can be easily pulverized with very little energy consumption through disk milling. The SPORL process can achieve over 90 percent cellulose conversion to glucose of the pretreated softwood and over 80 percent of the wood hemicellulose can be recovered as monomeric sugars in the pretreatment hydrolysate. Total fermentable sugar, glucose and mannose, recovery is over 84 percent with an ethanol yield of 73 gallons per ton of dry wood and a net ethanol production energy efficiency of 237 percent. Such high ethanol yield and net ethanol energy output from softwood have not been reported using competing technologies. The scalability and cost assessments of the SPORL technology for commercial production are more promising than existing technologies. The dissolved lignin in the SPORL pretreatment hydrolysate is sulfonated and has a great potential as a co-product for direct marketing. In this Phase II research we will demonstrate the SPORL technology at the pilot scale for efficient and economical production of cellulosic ethanol from forest biomass, especially softwoods. Together with the help of our university and industrial partners, we will optimize the process at the pilot scale and further evaluate pilot scale fermentation and the resulting sulfonated coproducts in an effort to produce a viable commercial technology. In Phase I of this project, we have demonstrated the great potential of SPORL pretreatment together with post SPORL pretreatment disk milling technology platform for effective removal of recalcitrance of lodgepole pine, a softwood, for cellulosic ethanol production. More importantly, different wood species also show the same response to the technology. This level of innovation provides BioPulping International and the SPORL technology a competitive edge in the highly competitive bioethanol industry. APPROACH: The work plan includes laboratory and pilot scale pretreatment and optimization as well as enzymatic saccharification and fermentation. There will be several tasks that will needed to be completed during the course of the project. The specific tasks for the proposed research are to conduct a process variation study of SPORL pretreatment integrated with size-reduction in a pilot scale facility, evaluate the physical and chemical properties of dissolved lignin from SPORL pretreatment in relation to the pretreatment conditions for direct marketable co-products, conduct high solids, 15 to 25 percent, simultaneous enzymatic saccharification and fermentation of SPORL solid substrate for maximal ethanol yield and minimal mixing energy consumption. Determine ethanol yield from fermentation of SPORL pretreatment hydrolysate, and finally to determine optimal process conditions based on ethanol yield, lignin co-product potential, and total process energy consumption in pretreatment, size-reduction, high solids saccharification, and distillation, estimated based on ethanol concentration.