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INVESTIGATOR: Naskar, A. K.

PERFORMING INSTITUTION:
UNIVERSITY OF TENNESSEE
2621 MORGAN CIR
KNOXVILLE, TENNESSEE 37996-4540

CONSTRUCTION-GRADE THERMOPLASTICS FROM ORGANOSOLV LIGNIN STREAM

NON-TECHNICAL SUMMARY: An undervalued lignin stream from an organosolv biorefining process will be converted into acrylonitrile-butadiene-lignin (ABL) to directly replace petroleum based plastics used in today's market. The proposed process allows for the production of the biofuel and industrial solvent, from the carbohydrates fraction and commodity products from the lignin steam. The high value of the lignin products will offset the biomass acquisition costs, thereby making the biofuel products more economically viable. Although the specific biorefining process applies to all softwood, hardwood, herbaceous, and agricultural residues, the proposed research will use hybrid poplar for its high syringyl alcohol content to maintain desired processing characteristics of the ABL and resulting products.

OBJECTIVES: The Center for Renewable Carbon at the University of Tennessee (UT-CRC) in partnership with Oak Ridge National Laboratory (ORNL), Natural Resources Research Institute at the University of Minnesota (NRRI), American Science and Technology Corporation (AST), University of Wisconsin Stevens Point (UW-SP), Long Trail Sustainability (LTS), and their industrial product manufacturer-Advanced Lignin Biocomposites LLC (ALB-LLC)- proposes to develop and commercialize solvent fractionated lignins to polymeric products for their potential market in building and construction sectors. The overarching objective of the proposed research is to reduce the nation's dependence on petroleum-derived chemicals through the development of integrated pathways for the extraction of value-added polymeric products from lignin waste/under-valued stream from biorefinery. The objectives also include the generation of process variables, and purity and performance data for the potential bioplastics for use in a detailed economic analysis and subsequent commercialization by our manufacturing team member (ALB-LLC) at a deployable cost. Ultimately, close interaction with industrial partners will be initiated for the deployment of the developed technologies. It is anticipated that our biorefinery-lignin that undergoes mild processing conditions compared to pulping mill-produced lignin would deliver superior polymeric products in terms of mechanical performance and olfactory response. To reach these project goals, we propose to develop cost-effective lignin isolation method from solvent fractionation of biomass followed by reactive processing routes to immediately produce commercializable formulations of lignin-based thermoplastics. These plastics along with variant compositions of melt-processible elastomers have the potential to significantly enhance the economics of biorefineries by being used for polymer matrix composite applications. Our initial results show that lignin from the current supply chain yields plastics with properties equivalent to those of general-purpose ABS resins. Successful isolation of lignin from solvent fractionation black liquor can augment the materials performance, significantly. The following three-pronged approach will be undertaken to achieve this goal. OBJECTIVE 1: Cost-efficient isolation of biomass constituents, lignin, cellulose, and hemicellulose via organosolv fractionation to recover lignin with high yield (>70%) and high purity (>90%); OBJECTIVE 2: Development and commercialization of lignin bioplastics with engineered properties and deployable cost for residential and commercial buildings' siding applications; OBJECTIVE 3: Assessment of the integrated biorefining process via techno-economic analysis and cradle-to-grave life cycle assessment (LCA) of the organosolv fractionation process; manufacture, use, and recycling/disposal of the new lignin bioplastics; and the solvent product.Our preliminary data provide the basis for the technical concepts, methods, and materials that will be deployed in this project. The proposed work is founded on recent patents and publications on lignin isolation through clean biomass fractionation, polymeric materials production and processing, and a preliminary LCA of the new organosolv lignin-based thermoplastic and solvent. A combination of resources for materials synthesis, processing, and characterization available at facilities of all the team members will be used to accomplish the overarching goal of the proposed research.

APPROACH: The approach proposed in this research is based on our recent results on commercially isolated lignin from biorefineries and pulping mills. In this project, we propose to use solvent fractionated lignin stream from an integrated biorefinery. This effort will help us gain a better understanding of the structure, processing, and properties of hybrid poplar biomass-derived plastics. The solvent-free direct reactive processing of isolated lignin or its composites to molded articles eliminate any need for the chemical functionalization of lignin. The materials produced in this approach are expected to have unique processibility like thermoplastics, be usable at higher temperature than the commercial bioplastics PLA and PHA, and have potentially equivalent/higher mechanical properties to those of petroleum-derived engineering plastics such as acrylonitrile-butadiene-styrene (ABS) polymer. This expectation is based on our preliminary data which indicate that lignin type affects final properties, primarily due to lignin's different chemical structures and associated reactivities during thermal extrusion and the molding process. The proposed work is founded on three pillars of investigation: (a) isolating lignin from hybrid poplar by solvent fractionation, (b) developing lignin bioplastics with engineered properties, and (c) TEA and LCA of the biorefining process and the products.

PROGRESS: 2018/01 TO 2022/12
Target Audience:Target audiences reached by our effort during this grant periodinclude bio-based industries seeking to develop new products from the lignocellulosic feedstock, scientific communities through presentations at professional meetings and conferences, publications in scientific journals, and general public events. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Throughout the grant, we provided research training for the post docs, graduate and undergraduate students who participated on this project. The training included one-on-one meeting on a weekly basis, regular presentations to internal and external audiences as well as research training in the lab. For the latter, the post docs, graduate and undergraduate students were provided the opportunity to advance their professional skills by learning from the project investigators and their lab members, identify the various barriers in product development and commercialization, and develop solutions that take into consideration the economical and environmental aspect of the system. How have the results been disseminated to communities of interest?Two journal articles have been published and those address methods to improve lignin self-assembly in a polymer matrix. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

IMPACT: 2018/01 TO 2022/12
What was accomplished under these goals? The project fractionated enough hybrid poplar to produce 50 kg lignin per batch in 3 different runs. The pulps were subsequently used for ethanol, butanol production verification via established fermentation routes and some cellulose pulps have been utilized to test lignin derived polymer reinforcing effects. Lignins of ~50 kg scale demonstrated >90% purity. These lignins when used in formulating an acrylonitrile-butadiene-lignin polymer via reactive extrusion of isolated ultra-pure lignin with a high acrylonitrile content to deliver performance enhanced product (>30 MPa tensile strength) that is processable to make extruded parts. The compositions show improved stiffness after incorporation of pulp as reinforcing phase. Close loop processing estimation (based on reported experimental conversion of cellulose to butanol) shows <10% loss of solvent during recovery step. However, residual furfurals from fractionation compensates some solvent loss. Nonetheless, 5:1 or higher solvent to dry poplar biomass is needed for feasible fractionation. The project team members participating in LCA-related aspects of the project have conducted a more thorough technical assessment of the organosolv fractionation and fuel production processes. Full cradle-to-grave processes were also developed for the ABL resin siding and two competing products (i.e., fiber-cement siding and polypropylene siding). During lignin production butanol (which is assumed to be 80% recycled and 20% virgin) accounts for between 45% to 61% of impacts in human health, cost, cumulative energy demand, climate change (kg CO2 eq.) and water use categories while heat from natural gas accounts for 5% to 36% of the impacts, and electricity use account for 6% to 45% of impacts. ABS resin production accounts for 29% to 70% of the impacts in each category and organosolv lignin production accounts for 10% to 19% of the impacts in each category. ABL resin production accounts for 65% to 83% of the impacts in each category, electricity consumption accounts for 5% to 19% of the impacts, and cellulose fiber accounts for 4% to 14% of the impacts.

PUBLICATIONS (not previously reported): 2018/01 TO 2022/12
1. Type: Journal Articles Status: Published Year Published: 2023 Citation: Kanbargi, N., Hoskins, D., Gupta, S., Yu, Z., Shin, Y., Qiao, Y., Merkel, D.R., Bowland, C.C., Labbé, N., Simmons, K.L. and Naskar, A.K., 2023. A renewable lignin-based thermoplastic adhesive for steel joining. European Polymer Journal, 189, p.111981.
2. Type: Journal Articles Status: Published Year Published: 2022 Citation: Rajan K, Keonhee K, Elder T, Naskar AK, Labbe N.* Ionic-liquid assisted fabrication of hybrid poplar thin films with tunable hydrophobicity, ACS Sustainable Chemistry and Engineering, 10, 8835-8845 (2022).