(332c) The 1st- and nth-Plant Cost Analyses for Incorporating Advanced Biomass Fractionation into Feedstock Processing Systems

The U.S. Department of Energy (DOE) Bioenergy Technologies Office (BETO) funds fundamental and applied research to advance the production of advanced liquid transportation fuels from lignocellulosic biomass. Corn stover is an important biofuel feedstock because it is a readily available, low-cost agricultural residue that does not compete with food production and has the potential to reduce greenhouse gas (GHG) emissions and promote advanced liquid transportation fuels development. Challenges exist in terms of logistics and variability in feedstock quality, and research efforts are underway to improve the efficiency of corn stover utilization as a sustainable and cost-effective biofuel feedstock. This study evaluates the 1^st-plant and n^th-plant costs for an advanced biomass fractionation and processing system to produce tissue fraction-enriched pellets from three-pass corn stover. The advanced biomass preprocessing system was developed by incorporating the results of BETO-funded research and development efforts conducted by INL. The resulting tissue fraction-enriched pellets could be converted in campaigns, taking advantage of their different degrees of recalcitrance, or blended based on their differing chemical compositions to meet the conversion critical material attributes (CMAs). Unused fractions could be sent to a value-added pathway to offset the system’s preprocessing cost. The n^th-plant analysis predicted modeled delivered costs of $78.80/dry ton (2016$), $79.17/dry ton, and $76.92/dry ton for the enriched husk, stalk, and cob pellets, and $56.15/dry ton for the enriched leaf fraction which was collected for use in the feed market and was not pelleted. The modeled weighted cost for the pellets delivered as the biorefinery feedstock was $78.64/dry ton. While the n^th-plant analysis assumed a constant quality feedstock, the 1^st-plant analysis utilized variability in the material to assess the impact. The average cost per ton of biomass (using the blending strategy) in the 1^st-plant analysis was $78.97/dry ton (2016$), which was $0.33/dry ton higher than the n^th-plant estimate. The 1^st-plant analysis also revealed that the average throughput was 1,823 dry tons/day or 82.69% of the name plate capacity, due to operability impacts that were dependent on the stochastic variability of the feedstock properties. After a year of operation, 638,152 tons (88.02% of the annual nameplate capacity) of preprocessed feedstock were produced; the variability in throughput was primarily caused by the interaction in flow rates amongst the different biomass fractions and the draw rates of the comminution line and densification line. Equipment failures in the system also contributed to the variability of throughput. The resulting Overall Operating Effectiveness (OOE) for the system, from the simulation, was found to be 74.8%. From this simulation, 84.98% of the preprocessed material met or exceeded the minimum quality specification, requiring the disposal of 15.2% of the biomass. When accounting for quality the average delivered cost of the material increased to $104.47/dry ton, ranging from $88.40 to $8,767.78. A feedstock performance factor of 84.98% and a fully burdened cost that is $25.83/dry ton higher than the estimated n^th-plant cost suggest that additional technology development is needed to further address the variability of quality within the feedstock to attain an OOE of 90% and cost parity with the n^th-plant analysis.