## 4 Breakout Sessions
(AHB research has shown that alternative jet fuel can be produced from poplar at $0.70 L\({}^{-1}\), well above current aviation fuel prices of $0.48 l\({}^{-1}\))  
The best way to accomplish all three is to move to a moderate scale production facility for demonstration and empirical testing: one that is small enough not to require more than $100 million in capital investment, but large enough to have acceptable economic returns. A modest scale biorefinery, especially a first-generation factory, will require substantial policy support to be economically viable. Concurrently, attention should be focused on how to build scale to improve economics for the long term. This recommendation is based on the panel's experience that moving directly to commercial-scale refinery construction has often involved contractors with the wrong expertise; one panelist spoke of constructing fermentation tanks using vendors who had never made fermenters leading to problems with tank finish and subsequent contamination. Another panelist mentioned that it may be difficult to enlist top contractors to take on the design and construction of small-sized biorefineries when their primary attention is drawn to larger projects in the pulp and paper sector. The panel also recommended that the region's first commercial plant should co-locate with existing industrial complexes that offer affordable infrastructure and cost-sharing. As an example, the TerraPower representative stated that his company's nuclear power generation could provide low-cost, excess process heat under 290 \({}^{\circ}\)C to reduce the cost of power production at a nearby biorefinery. The Pacific Northwest paper industry may be potentially interested in a similar arrangement based on reports of retooling pulping operations to extract acetic acid and hemicellulose from pulping streams under mild conditions for co-product production while maintaining fiber quality and quantity [42; 43]. Sulfite pulp mills offer a unique opportunity for co-location as they have a sugar rich waste stream that could be readily fermented to produce fuels and chemicals. A second idea to lower operating cost was to address the dilution factor of products coming from the fermenter that not only affects the refinery operating costs, but also a refinery's energy footprint.  
The panel felt a simpler conversion process is warranted, especially one featuring a less-expensive pre-treatment process. Consolidated bioprocessing (CBP)--co-treatment with cellulolytic anaerobes to improve the efficiency of cell wall deconstruction and carbohydrate solubilization--and co-treatment were presented during the opening keynote as one way to simplify the conversion process. The merits of CBP in reducing biorefinery operational steps and chemical inhibitors were discussed as early as 2012 [44]. Questions were raised as to the likelihood that the CBP approach can take woody material to alcohol fuels without pre-treatment and added enzymes. Accordingly, the consensus was for AHB to continue its focus on the current approach promoted by NREL, Zeachem and others, but to support research and development of novel approaches such as CBP.  
One innovative approach being pursued at the University of Washington is increasing the amount of sugars recovered during the pre-treatment and enzymatic hydrolysis by biomass pre-processing with neutral or acidic washes. Removal of ash and extractives also exhibits increases in fermentation ethanol yields. This led to a panel discussion about the advantage of poplar and willow in pre-treatment compared with other non-woody perennial feedstocks; grasses have a higher ash content and therefore consume more chemicals during their removal. Residual supplies--both agricultural and forestry--are similarly disadvantaged by soil particles picked up during harvest and baling operations. The panel also discussed thermo-conversion approaches. The panel recognized the potential of these technologies, but advised caution citing commercial failures with pyrolysis and gasification. It was noted, however, that Velocys and others are active in developing gasification/Fischer-Tropsch as an alternative conversion technology. Also mentioned was Shell/CRI continuous catalytic thermo-chemical process (IH\({}^{2}\) technology) in India, and Ensyn/UOP Rapid Thermal Processing for both refinery co-processing and stand-alone upgrading of pyrolysis oil.  
The panel endorsed the production of bio-based chemicals in place of or co-produced with fuels based on AHB conversion economics. This is in line with reports that future biorefineries will encompass multiple process streams to produce transportation fuels, co-products, and direct energy [35]. Production of chemicals enables smaller factories, offers better carbon benefits, and may facilitate the targeting of less volatile markets (these markets often utilize petroleum by-products and may be similarly price-challenged in the current environment of low-cost oil). Process streams with good economic potential include those derived from poplar foliage (e.g., natural pesticides) and the xylose-rich liquid stream produced after steam explosion. Valuable fermentation products include alcohols, acids, aldehydes, esters, and various nitrogen- and sulfur-containing compounds used in flavor enhancers, fragrances, and personal care products. Studies were quoted that acetic acid can be produced at a cost of $300 Mg\({}^{-1}\), well below the current selling price of about $500 Mg\({}^{-1}\)[45]. Organic acids and sugar alcohols were mentioned as having similarly favorable economics. These will require separation of the five- and six-carbon sugars which can be easily done following the pre-treatment. Mention was made of the importance of extracting lignin in its reactive form for manufacturing carbon fibers. The panel noted that the use of a variable raw material such as lignin is challenging, and that commercialization of a reliable process may be some ways off.  
Markets and Policy--The panel agreed with prevailing projections that oil prices may vary considerably, but will stay below $80 a barrel at least for the next five years, perhaps longer.