conversion by reducing the amount of material that would need to be transported to larger processing facilities for conversion to sugars while also providing an energy source to support local industry.

The major technological and commercial barriers to scaling up sustainable technologies involve moving from batch processing to continuous processing, at least up to the stage of sugar production. It was noted by several breakout group members that batch processing of biomass to produce sugar on a scale needed to produce 21 billion gallons of ethanol a year by 2022 was untenable economically. Producing that much ethanol in batch fermentation plants would require 525 40-million-gallon plants at $40 million apiece.

Most breakout group members believe that fuel production and chemical production should be considered separate pathways, much like they are in the petrochemical industry. While many breakout group members agreed that fuel production from sugars via fermentation should be done through a continuous process to be truly economical and scalable, production of most chemicals is best done in batch mode, at least based on the extensive experience of the chemical industry. It was noted during the discussion from a member of the group that 90 percent of organic chemicals used today are made in batch operations. This percentage reflects the production of the many hundreds of specialty chemicals which are done in relatively small batches, whereas the top 100 commodity chemicals, which represent by mass the bulk of synthesized organic chemicals, are produced in continuous-flow batches. The chemical industry is already exploring the production of chemicals from biomass independent of fuel production.

The breakout group discussed the need to solve technological issues involving economical production of enzymes to meet a variety of demands. Many members of the group concurred that technology development was needed to design enzymes with higher activities, that could pretreat biomass prior to sugar production, that would resist inhibition by lignin or organic acids, and that will function in alternative environments, such as in ionic solvents or under pressure. There was substantial discussion, with no consensus, about whether it was better to build better and less expensive enzymes or to engineer microorganisms to that can perform multiple steps in the conversion process. The suggestion was made that the biomass field could learn from the pharmaceutical industry, which makes extensive use of secondary metabolism by engineered microorganisms to produce high-value products. The breakout group also noted the need to develop methods for conducting large-scale anaerobic fermentation to achieve more efficient conversion of sugars to product.

Addressing the issue of needed skills, the breakout group concurred that fundamental process engineering is “a dead field” that attracts little interest among researchers and few funding opportunities, but that this field should be reinvigorated if technological barriers are to be addressed. What little process engineering research does occur is largely conducted overseas. The same appears to be true for separations technology and surface chemistry, and the breakout group agreed that chemists need to receive better training in these key technological fields. Some members of the group highlighted the need for universities to establish biofuels courses which has already been done at the University of California, Berkeley. Some group members noted the need for biochemists to receive more training in enzymology, a field that once flourished.

According to Katz, members of the group said chemical engineers also need a new set of skills to contribute to the development of a biomass-based industry. Chemical engineers today receive very little training in batch processing or in the design and operation of continuous enzymatic processes. Both of these deficits need to be addressed immediately, according to the breakout group members, Katz said.

Turning to issues of transportation infrastructure, the individual breakout group members concurred that the costs of biomass collection and transportation needed to be addressed if biomass is to make a significant contribution to the production of fuel and chemicals. The members of the group said that the biomass industry will have to depend on the existing transportation infrastructure given the huge expense of creating a new one. It was noted during the breakout group discussion that $4 billion was invested in an ethanol pipeline system that is only at 25 percent of capacity now.

One idea from the group was that it may be necessary to subsidize stover collection by secondary harvesting services to meet supply considerations if the market develops for the products of biomass conversion given that there is little economic incentive today for farmers to collect stover. The group also noted that storage of corn stover or corn cobs, which could also be a good source of biomass, is expensive and is actually a significant economic barrier that needs to be addressed. The breakout group raised the idea of developing a slurry-based pipeline system for biomass or a system for converting biomass into pellets for easier transport.

The breakout group concluded its discussions with a comment about the idea of converting biomass to so-called drop-in fuels versus expanding the amount of ethanol produced. The group said that it is hard to compete with ethanol in terms of net energy return from sugar because ethanol’s high oxygen, low carbon content closely matches that of sugars. For advanced biofuels based on hydrocarbons, fatty acids produced by algae or oil crops are likely to be the better feedstock.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement