With growing interest in the biomass value chain, a multitude of reactions are proposed in literature for the conversion of biomass into a variety of biofuels. In the early design stage, data for a detailed design is scarce rendering an indepth analysis of all possibilities challenging. In this contribution, the screening methodology process network flux analysis (PNFA) is introduced assessing systematically the cost and energy performance of processing pathways. Based on the limited data available, a ranking of biorefinery pathways and a detection of bottlenecks is achieved by considering the reaction performance as well as the feasibility and energy demand of various separation strategies using thermodynamic sound shortcut models. PNFA is applied to a network of six gasoline biofuels from lignocellulosic biomass. While 2-butanol is ruled out due to a lack in yield and selectivity, iso-butanol and 2-butanone are identified as economically promising fuels beyond ethanol. Topical area: Process Systems Engineering.

A large number of alternative fuel molecules based on lignocellulosic biomass have been proposed recently, but a reliable evaluation of their economic potential is challenging due to the limited data available. A rapid screening methodology, Reaction Network Flux Analysis (RNFA), has been suggested to screen a large number of future reaction pathways. The RNFA is extended in this work by a comprehensive sensitivity analysis to account for inevitable uncertainty in the underlying data and hence in the ranking of biofuel candidates with respect to cost and environmental impact. The extended RNFA is then used to assess and rank candidate reaction pathways and associated processes for the production of a variety of proposed future pure-component biofuels from lignocellulosic biomass. Ethyllevulinate and 2-methyltetrahydrofuran have been identified as promising alternatives to bioethanol, while lignin-based biofuels can be excluded from further consideration. Methane is found to be attractive economically but shows significant environmental impact.

As renewable electricity sources emerge, the conversion of electricity and CO 2 to carbon-based fuels (e-fuels) arises as a complementary or competing option to biofuels. This work provides a systematic performance comparison of both bio-and e-fuel pathways to identify characteristic differences and optimal applications of both production types. We construct a reaction network that features biochemical and thermochemical conversion of lignocellulosic biomass, transesterification of waste vegetable oil, and e-based routes (E-routes) using renewable H 2 . The network is optimized for economic and environmental criteria using two pathway screening tools, i.e., Reaction Network Flux Analysis and Process Network Flux Analysis. Furthermore, we apply a linear combination metric to analyze the advantages of bio-e-hybrid designs on a global fleet level. The results show that lignocellulosic-based fuels are relatively inexpensive but typically incur energy-intensive separations and high carbon losses. E-routes, on the contrary, result in only small carbon losses and global warming potentials as low as 5 g MJ CO 2 ,eq. fuel . However, they come at high cost due to the use of expensive renewable H 2 . When combinations are considered, biomass can be utilized by upgrading it with e-based H 2 . In the case of bio-e-hybrid ethanol plants, co-fermentation of sugars and utilization of CO 2 emitted during fermentation are identified as viable low-cost options for carbon loss reduction. These hybrid pathway designs outperform combinations of purely bio-based and purely e-based pathways at the fleet level.

Even though a shift from conventional to renewable resources is often envisaged, lignocellulosic biorefinery concepts struggle with economic viability and sustainability. In order to overcome these barriers, a full analysis from biomass supply chain, process performance optimization, and product-portfolio selection is targeted. Addressing the economic viability and sustainability already at an early process development stage when only limited knowledge is available, Process Network Flux Analysis (PNFA) [Ulonska et al., AIChE J. 2017, 62, 3096−3108] is capable of systematically identifying the most valuable processing pathways. This enables a first performance ranking based on the profit or global warming potential of pathways, thereby accelerating process development. While so far only processing networks have been considered, the methodology is herein extended to consider biomass supply chain optimization and market-dependent price developments such that all main influencing factors are considered simultaneously. The extended methodology is validated identifying reasonable plant locations in North Rhine-Westphalia, Germany. Enhancing economic viability of the best performing biofuel ethanol, a multiproduct biorefinery is targeted coproducing value-added chemicals. Herein, a coproduction of iso-butanol raises the profit significantly: a mass ratio of at most 1.9 (ethanol:iso-butanol) is required to break even.

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