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This study demonstrates a failure identification methodology applied to a preprocessing facility generating conversion-ready feedstocks from biomass meeting conversion process critical quality attribute (CQA) specifications. Failure Modes and Effects Analysis (FMEA) was used as an industrially relevant risk analysis approach to evaluate a logging residue preprocessing system to prepare feedstock for pyrolysis conversion. Risk evaluations considered both system-level and operation unit-level assessments considering process efficiency, product quality, cost, sustainability, and safety. Key outputs included estimations of semi-quantitative risk scores for each failure, identification of the failure impacts, identification of failure causes associated with material attributes and process parameters, ranking success rates of failure detection methods, and speculation of potential mitigation strategies for decreasing failure risk scores. Results showed that deviations from moisture specifications had cascading consequences for other CQAs along with process safety implications. Failures linked to fixed carbon specifications carried the highest risk scores for product quality and process efficiency impacts. As increased throughput can be inversely related to meeting product quality specifications; achieving throughput and other material-based CQAs simultaneously will likely require system optimization or prioritization based on system economics. Ultimately, this work successfully demonstrates FMEA as a risk analysis approach for other bioenergy process systems. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the economic feasibility of the hydrothermal carbonization (HTC) of waste corn stover. Two different cases of HTC of waste corn stover were considered for a 544 320 kg day−1 as‐received corn stover plant. Case I assumed a batch HTC process, and case II assumed a continuous HTC process. The results show that both cases were economically feasible; however, case I reached the break‐even point at 3 years whereas case II reached the break‐even point at 4 years. Case I also showed greater return on investment (5.02) than case II (3.98) at the end of the 20 year project life, including 26.6% lower total capital investment. About 73% of fixed capital cost came from investment in the reactor alone for case I, whereas 63% came from the reactor for case II. The break‐even selling price of the product was found to be $86.1/kg. A sensitivity analysis showed that the break‐even selling price of the product was the most sensitive to the variation of the cost of corn stover and the least sensitive to variation in the tipping income. [ABSTRACT FROM AUTHOR]

Highlights • Microwave-enhanced fast pyrolysis is reported for heating rates of 1–50 °C/s. • 33 Biomass samples and blends were tested for feedstock composition impacts. • Mineral content and volatile matter accounted for the most liquid yield variability. • The same parameters also predicted water and acid content in the liquid product. • Observed bio-oil yields did not increase for heating rates >10 °C/s. Abstract The products from fast pyrolysis of biomass are variable and highly dependent upon feedstock composition, particle size and geometry, and operating conditions such as heating rate, reaction temperature, and sweep gas composition and velocity. Microwave heating is internal to the biomass particles, thereby avoiding convective and conductive heat transfer limitations, which facilitates decoupling heat transfer effects from chemical reaction kinetics. This separation allows for elucidation of the primary effects of the original materials’ composition on product yields. To better understand the interconnectedness of biomass composition and fast pyrolysis (pyrolysis liquid oil yield in particular), a high throughput microwave-enhanced fast pyrolysis (MEFP) reactor was used to react 33 biomass samples with a minimum of three replicate tests each. The materials in this study included: woody feedstocks (with and without bark), agricultural residues, herbaceous energy crops, and blended feedstocks. The highest liquid yields were obtained from lumber (66.2 wt%) and tulip poplar (64.9 wt%), while the lowest yields were obtained from sorghum (47.8 wt%) and single-pass harvested corn stover (48.5 wt%). Liquid yields had an average standard deviation of 1.4 wt% (average 2.5% relative standard deviation). The MEFP achieved heating rates up to 200 °C/s, however, beyond 10 °C/s liquid oil plateaued with increasing heating rate. Multivariate regression of pyrolysis yields with over 20 feedstock properties, obtained through detailed compositional analysis, indicates that aggregated alkali and alkaline Earth metals (primarily K and Na, along with Ca and Mg) accounted for the most variability among liquid yields (R 2 = 0.71). Addition of volatile matter as a second predictor variable achieved the greatest reduction of the model residuals to increase the coefficient of regression (R 2) to 0.85. Liquid yield water fraction increased linearly with feedstock potassium and sodium content over a much wider range than previously observed. Pyrolysis oil acid content was found to increase with increasing volatile matter and decreasing potassium and sodium content. [ABSTRACT FROM AUTHOR]