Performing Department
Chemical Engineering
Non Technical Summary
Forest residue biomass (FRB) generated from harvesting operations, including tops and branches and low-grade material, has the potential to provide over 150 million Mg (dry) biomass annually in the U.S. and is one of the lowest cost feedstocks available. The development of sustainable technologies for utilization of FRB for biofuels and bioproducts production can provide a renewable source of green products and fuel, along with addressing environmental concerns. However, there is currently no proven sustainable technology for large or small-scale conversion of FRB. The barriers are related to natural recalcitrance of biomass, partial utilization of biomass, low-value products, and byproducts, and high capital and operating processing costs. Through this project, we propose an innovative hybrid process integrating biological and thermochemical conversion to co-produce bioplastics (polyhydroxybutyrate; PHB) and biofuel (bio-oil) from forest residues biomass (FRB). The sugars obtained from the hydrolysis of structural carbohydrates will be fermented to producePHB, a biodegradable thermoplastic; while, the lignin-rich residues will be processed to produce energy-dense bio-oil. The conversion process will maximize resource-use efficiency, water use, and overall energy efficiency. Techno-economic analysis (TEA) and life cycle analysis (LCA) will be conducted to choose maximally efficient process conditions. PHB is an important bio-based thermoplastic polyester with performance characteristics similar to polypropylene and biodegrades entirely into CO2 and H2O. Bio-oil is a superior quality fuel with low oxygen content and high heating value that can be efficiently upgraded to renewable diesel via hydrotreatment. Bioplastic and renewable diesel are of critical importance due to high market value, environmental benefits, and potential market demand due to recent policies.
Animal Health Component
0%
Research Effort Categories
Basic
(N/A)
Applied
50%
Developmental
50%
Goals / Objectives
The overall objective of this work is to develop and model a sustainable biological-thermochemical hybrid processing system for FRB valorization to bioplastics and biofuel, which is robust, energy-efficient, able to use different mixtures of forest residue, and is economically feasible and environmentally friendly. The specific objectives for this proposal are to:Investigate the effect of pretreatment conditions on the PHB production yields from FRBDetermine the process yields and product characterization from HTL of lignin-rich residueDevelop TEA and LCA modeling framework to determine economic feasibility and environmental impact
Project Methods
Task 1. Biomass collection and characterizationFRB from sugar maple (Acer saccharum) will be collected from the Heiberg forest. Biomass samples will be oven-dried at 45ºC andground using a Wiley mill to pass through a 2-mm sieve, before further processing. The chemical composition of biomass samples will be determined by the wet chemistry method using standard Laboratory Analytical Procedure (LAP) from the National Renewable Energy Laboratory (NREL). Moisture and ash contents in the samples will be determined using gravimetric methods with oven drying and muffle furnace.Task 2. Biomass pretreatment, hydrolysis, and PHB productionSubtask 2.1 Pretreatment and hydrolysis of FRBIn the first step, hot water pretreatment will be performed using a lab-scale Parr reactor. A range of process parameters (temperature, time, and solid content) will be chosen based on previous studies in the literature, and experiments will be conducted at specific conditions determined using a central composite design. The recovered slurry from the reactor will be processed through a lab-scale disk mill. The slurry obtained after disk milling will be subsequently hydrolyzed using commercial cellulase and hemicellulase enzymes. After completion of hydrolysis, liquid and solid fractions will be separated using vacuum filtration. Weights of slurries and moisture will be determined at each step for mass balance. The C5 and C6 sugar concentrations in the liquid will be determined using HPLC.Subtask 2.2 PHB productionThe liquid fraction containing sugars (from subtask 2.1) will be fermented using recombinant E. coli LSBJ to produce PHB. The fermentation experiments will be performed for 48 hours. Microbial biomass (containing PHB) will be harvested after fermentation by centrifugation, washing, and lyophilizing for gravimetric determination of cell yield. PHB content of the cell biomass will be measured using gas chromatography (GC) equipped with a flame ionization detector.Task 3. Hydrothermal liquefaction of lignin-rich residuesThe solid stream resulting from subtask 2.1 and liquidobtained after cell separation in subtask 2.2 will be processed through HTL in a lab-scale batch Parr reactor. For this work, one set of HTL process conditions (temperature, time, and solids-water ratio) will be chosen based on previous studies in the literature and kept the same for all experiments. The gases produced will be collected in a gas sampling bag for analysis. The slurry in the reactor will be mixed with dichloromethane (DCM) and vacuum filtered. The solid fraction will be dried at 105 °C for several hoursto obtain the yield of solid residues. The filtrate will be extracted with dichloromethane (DCM) using liquid-liquid extraction in a separatory funnel. The DCM insoluble fraction will be weighed to determine the yield of aqueous products. Bio-oil from the DCM-soluble fractions will be recovered after evaporating the DCM in rotary evaporators.Task 4. Techno-economic and life cycle analysis of the integrated systemComprehensive process models will be developed for various production scales using SuperPro Designer (Intelligen, Inc., NJ, USA). The experimental results from tasks 1-3 will be used as inputs for the model simulations. The data related to bio-oil to renewable diesel upgradation will be extracted from the scientific literature. Equipment design specifications and cost data will be obtained from the process models developed by the PI and other researchers for other cellulosic biorefineries, PHB production, and thermochemical processes.A stochastic LCA model will be developed to quantify the environmental impact of the process. This assessment will follow the framework defined by the International Standardization Organization (ISO). The environmental impact of the end products will be characterized according to the Tools for Reduction and Assessment of Chemicals and other environmental Impacts (TRACI) method. The system boundary will include all the steps from forest biomass handling and preprocessing to conversion and recovery of the final products. The GHG emissions and minimum selling prices of the PHB and renewable diesel will be compared with their fossil-based alternatives to calculate their carbon abatement cost.