PNNL

Abstract

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 production of target fuels from renewable feedstocks and conducted techno-economic analysis (TEA) and life-cycle assessment (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 are still being assessed. Twelve pathways showed significant reductions in lifecycle 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 the GHG emissions. Results from these analyses enable researchers and industry to assess the potential viability of MCCI bioblendstocks.