Conceptual Process Design of an Integrated Xylitol Biorefinery With Value-Added Co-Products

Abstract

This manuscript describes the conceptual process design of an integrated xylitol biorefinery with value-added co-products. Based on an existing three-step framework, the main product of a second-generation integrated biorefinery is chosen in the first stage. Based upon this, other decisions as the feedstock and value-added co-products are made. All relevant unit operations for the process are introduced. An initial superstructure with all potential process alternatives is composed of all introduced models. In the second step of the framework, a global sensitivity analysis is performed, firstly with coarse sampling to determine all viable flowsheet options and secondly with fine sampling to determine the most sensitive operational variables. As a result of the sensitivity analysis, most of the flowsheet options in the initial superstructure are not feasible. Based on these results, flowsheet sampling with the five most sensitive operational variables is performed to create surrogate models. In the scope of this work, three types of surrogate models are benchmarked against each other. Regarding the results of the superstructure optimization, firstly, it becomes apparent that the production of biokerosene does not contribute significantly to the net present value of the biorefinery. Furthermore, reducing the number of unit operations in the downstream processing leads to lower capital expenditures, but it lowers the product yield. Lastly, most flowsheets are economically feasible, indicated by a positive net present value. Based on this result, the most promising candidate process topology is subjected to the third step of the framework, including uncertainty in capital expenditure and operational expenses according to their estimations and uncertainties in the product prices. As a result, the net present value of the flowsheet turns negative, indicating that the high uncertainties for the expenditure and the expenses do not allow for an economically feasible operation. Lastly, the analysis of conceptually designed process flowsheets based on Monte Carlo sampling shows failure rates, with the NPV falling below the break-even point, of around 60% probability or higher. Based on these results, an economically feasible construction and operation of a xylitol biorefinery seems unlikely. Further ways to improve the metrics are elucidated.

Design of an integrated biorefinery for bioethylene production from industrial forest byproducts

“…The variables that most affect the profitability of the proposal are economic factors, 13,16 for example, selling prices, 10,13 feedstock 72,73 and reagents 74 costs, others; and technical or operational factors, 75 for example, the LSR of pretreatment, the steam economy, and others. 71…”

“…After selecting the variables, their limits and adjusted curves have to be defined. 16,71 The variables that most affect the profitability of the proposal are economic factors, 13,16 for example, selling prices, 10,13 feedstock 72,73 and reagents 74 costs, others; and technical or operational factors, 75 for example, the LSR of pretreatment, the steam economy, and others. 71 Table S1 of the ESI † shows each factor considered in the present study.…”

Multi-feedstock biorefinery concept: Valorization of winery wastes by engineered yeast

“…Therefore, the selection of the most appropriate high-value products to complement the production of low-value biofuel in a biorefinery is crucial for achieving high profitability. The sugar-alcohol xylitol is included in the US Department of Energy list of high-value compounds that can be produced from biorefinery carbohydrates (Werpy and Petersen, 2004;Baptista et al, 2021) with a current market price of 7.95 €/kg (Vollmer et al, 2022). A recent techno-economic analysis of a lignocellulosic biorefinery for the production of xylitol coupled with a Coefficients significant at the 99% confidence level.…”

Life cycle assessment of an integrated xylitol biorefinery with value-added co-products

“…After the enzymatic hydrolysis, the lignin is transferred to combustion with an included steam and power generation unit. Furthermore, the xylitol biorefinery comprises a wastewater treatment unit (Vollmer et al 2022c). The entire conceptual process flowsheet, partly excluding the auxiliary unit operations, is displayed in Fig.…”