Aviation and certain other transportation sectors are likely to continue to require liquid hydrocarbon fuels in the long term even as light duty transportation shifts to alternative energy sources. Professor George Huber leads a multi-university team that has addressed challenges of introducing advanced biofuels in the transportation pool through the concerted development of technology designed to transform lignocellulosic biomass into a jet fuel surrogate via catalytic chemistry.

The team’s promising approach highlights the versatility of lignocellulose.

The proposed technology hinges on efficient production of furfural and levulinic acid from sugars that are commonly present in lignocellulosic biomass. These two compounds are then transformed into a mixture of chemicals that are indistinguishable from the primary components of petroleum-derived aviation fuels.

Lignocellulosic Biorefinery Process Diagram.  Image Credit: J Bond, Syracuse University.

Lignocellulosic Biorefinery Process Diagram. Image Credit: J Bond, Syracuse University.

Huber, working at the University of Wisconsin-Madison, has addressed both challenges through the concerted development of technology designed to transform lignocellulosic biomass into a jet fuel surrogate via catalytic chemistry.  Lead author Jesse Q. Bond, Syracuse University Assistant Professor of Biomedical and Chemical Engineering explored the team’s work with lignocellulose as a feedstock as recently summarized in the journal Energy & Environmental Science.

Utilization of advanced biofuels is stipulated by the Energy Independence and Security Act; however, current production levels lag behind proposed targets. The key challenge in the biofuel market is to get more advanced biofuels – fuels beyond common corn ethanol and vegetable oil-based biodiesel – into the transportation pool.

Lignocellulosic biomass is an abundant natural resource that includes inedible portions of food crops as well as grasses, trees, and other “woody” biomass. According to the United States Department of Energy, the United States could sustainably produce as much as 1.6 billion tons of lignocellulose per year as an industrial feedstock.

Lignocellulose can be processed to yield various transportation fuels and commodity chemicals. But current strategies are not generally cost-competitive with petroleum.

Huber’s team presents a comprehensive approach toward streamlining biomass processing for the production of aviation fuels. The technology was demonstrated through a multi-university partnership that brought together expertise in biomass processing, catalyst design, reaction engineering, and process modeling.

Economic analysis suggests that, based on the current state of the technology, jet fuel-range hydrocarbons could be produced at a minimum selling price of $4.75 per gallon. The team’s work also identifies primary cost drivers and suggests that increasing efficiency in wastewater treatment and decreasing catalyst costs could reduce that amount to $2.88 per gallon.

Professor Bond overlooks the new technology with, “This effort exemplifies the impact of a well-designed collaboration. As individual researchers, we sometimes focus too narrowly on problems that we can resolve using our own existing skills. Biomass refining is complex, and bio-based aviation fuels are difficult targets. Many of the real roadblocks occur at scarcely-studied research intersections. In our view, the only meaningful way to tackle these challenges is through strategic partnerships, and that is precisely what we’ve done in this program.”

The combined research areas highlighted include biomass pretreatment, carbohydrate hydrolysis and dehydration, and catalytic upgrading of the platform chemicals. The technology centers on first producing furfural and levulinic acid from five- and six-carbon sugars present in hardwoods and subsequently upgrading these two platforms into a mixture of branched, linear, and cyclic alkanes of molecular weight ranges appropriate for use in the aviation sector.

The work results in hemicellulose sugars that could be incorporated into aviation fuels at roughly 80% carbon yield, while cellulose-based sugar carbon yields to aviation fuels are only on the order of 50%.

What we come away with are the lessons that the paper shows in the abstract. Using lignocellulose-derived feedstocks rather than commercially sourced model compounds in process integration provided the team important insights into the effects of impurity carryover and additionally highlighted the need for stable catalytic materials for aqueous phase processing, efficient interstage separations, and intensified processing strategies.

Nowhere close to field ready, the research does show the development path is workable. Impurity carryover, efficient interstage separations, and intensified processing strategies look like a process or batch problem, a field for engineers. The catalysts are coming from a rapidly evolving field that has obsolete ideas and new ones by the month. Its a good start on what will likely be the longest lived petroleum based fuel market


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