Economic and environmental favorability are vital considerations for the large-scale development and deployment of sustainable fuels. Here, we have conducted economic and sustainability analyses of pathways for producing bioblendstocks optimized for improved combustion for mixing-controlled compression ignition (MCCI) engines. We assessed 25 pathways for the production of target fuels from renewable feedstocks and conducted technoeconomic analysis (TEA) and life cycle analysis (LCA) to determine which bioblendstock candidates are likely to be viable given a slate of 19 metrics evaluating technology readiness, economic viability, and environmental impacts ranking each metric as either favorable, neutral, unfavorable, or unknown across a range of screening criteria. Among the results, we found that the economic metrics were largely favorable for most of the bioblendstocks. Of the near-term baseline cases, eight pathways offered the potential of a minimum fuel selling price (MFSP) of less than $5/gallon of gasoline equivalent (GGE). In comparison, under future target case scenarios, there is potential for seven pathways to reduce their fuel selling price to less than $4/GGE. Biochemically-based pathways struggled to achieve favorable target case MFSP under the processing approach taken here, but further economic improvements could be achieved when lignin valorization is included. Most of the conversion technologies were determined to be robust in that they would be minimally affected by the feedstock specifications and variations. However, given the early stage of development for most of the pathways, blending behavior and testing for regulatory limits are key data gaps as knowledge of how many of these bioblendstocks will perform when blended with existing fuels and how much can be added while still meeting fuel property specifications is still being assessed. Twelve pathways showed significant reductions in life cycle greenhouse gas (GHG) emissions greater than 60%, and 15 showed favorable fossil energy use reductions compared to conventional diesel fuel. Energy-intensive processes and the use of GHG-intensive chemicals such as sodium hydroxide contribute significantly to GHG emissions. Results from these analyses enable researchers and industry to assess the potential viability of MCCI bioblendstocks.

Due to challenges related to weight and travel distance, the medium to long-haul aviation sector is expected to remain reliant on liquid hydrocarbon fuels into the foreseeable future, representing a...

Hydrogen storage is a key technology for enabling the decarbonization of future energy systems, but is subject to low volumetric density in the case of compressed hydrogen. Chemical conversion to a liquid hydrogen carrier can overcome this challenging issue. For example, the reversible reaction of 1,4-butanediol (BDO) to γ-butyrolactone releasing two moles of hydrogen could be an attractive option for storing and transporting hydrogen. Herein, the thermodynamics of both, the reaction and the process, are evaluated. An important question that should be answered is whether there is a difference in energy efficiency between this reaction being performed in the liquid and in the gas phase. The thermodynamic analysis showed that heat demand for evaporation from the liquid to the gas phase is a major drawback of gas-phase reactions even though the enthalpy of reaction is somewhat smaller in the gas than in the liquid phase. However, due to the vapor pressure of BDO, there is some evaporation occurring in the case of liquid-phase reactions at reaction temperatures required to release hydrogen. This evaporation reduces the energy benefits of the liquid-phase reaction. As a consequence, the round-trip efficiencies of both options (liquid-and gas-phase reaction) are similar (varying by <5%). This is an advantageous finding as it allows selection of reaction conditions (liquid-or gasphase reaction) solely based on catalytic considerations, without major restrictions due to concerns from process engineering.