away from aromatics. Brown responded that aromatics are expected to be an important component of fuels for some time to come. They are particularly produced by catalytic pyrolysis using zeolites, but through further research alkanes might instead be produced.
Mark Barteau, from the University of Delaware, asked if co-processing of biomass with natural gas might be a way of shifting the carbon-hydrogen-oxygen ratio without using expensive hydrogen. Brown replied that with natural gas at the $2 level, this idea makes perfect sense and could provide a bridge to advanced drop-in biofuels. Helena Chum, from NREL, asked about the optimal scale for biomass processing, and Brown said that the issue of scale has to balance the fact that larger plants are probably offering economies of scale as far as process and capital costs are concerned, but that larger plants also have increased costs to transport biomass. He guessed that the optimal size for a plant that converted thermolytic substrates into transportation fuels would be somewhere in the 2000–3000 tons per day range although distributed processing facilities might be substantially smaller.
This breakout session was led by Douglass Elliott, of the Pacific Northwest National Laboratory, and the discussions began with the participants noting that there are a number of large-scale (greater than 500 tons per day of biomass) and pilot-scale (under 50 tons per day of biomass) demonstration projects, for both gasification and pyrolysis, either under construction or in the planning stage. The group acknowledged that gasification technology, while well proven with other feedstocks such as coal, may to struggle to compete with cheap, abundant, long-term supplies of natural gas. Having said that, many breakout group participants concurred that gasification is likely to be “omnivorous”; that is, it is likely to be adaptable for use with a wide variety of feedstocks. It was suggested, in fact, that while natural gas is the feedstock of choice today, it could serve as a bridge technology to biomass feedstocks in the future. Another suggestion was to integrate a corn stover gasifier into corn ethanol plants. Lignin and unconverted sugars could also be mixed into the corn stover for gasification. It was noted that such a plant is on the drawing board.
The breakout group discussed the use of gasification or natural gas to upgrade the bio-oil produced by pyrolysis and thought this was worth exploring. It was noted that Finland has been adding small pyrolysis chambers to existing fluidized bed combustion boilers. The pyrolysis unit uses some of the heat from the boiler system and in return feeds char and other byproducts of pyrolysis back into the boiler’s combustion chamber.
Turning to the subject of technological and commercial barriers, the breakout group noted that economic analyses and life cycle analyses are missing from most thermochemical conversion studies, particularly for combined systems. Some participants suggested that such studies be funded because there are many interesting concepts being developed today, but there is little thought being given to cost analysis. In the same vein, the breakout group described the need for better coupling of basic, translational, and applied research studies and noted that DOE could help fill that gap.
Another area of research that needs to be bolstered, some group participants noted, concerned the development of technologies to efficiently handle biomass solids of different characteristics and to determine how to best mix different biomass sources to produce bio-oil with more consistent properties. Some members of the breakout group also identified the need to develop methods for feeding biomass feedstocks into reactors at pressure, to design catalysts that are more tolerant of the poisons in biomass and of water and steam, and to perform separations at lower energy intensity. A basic research question that still needs answering, according to many breakout group members, was whether it might be best to process biomass as fractionated components rather than as the natural biocomposite that is lignocellulosic biomass.
The breakout group briefly discussed the belief that most efforts today focus too much on market “push” and not enough on market “pull.” In other words, the many members of the group noted, research was needed to identify products that could be made in an economically competitive manner from bio-oil or syngas. One approach to developing market pull that is being followed to some extent, the group noted, is to demonstrate how bio-oil or syngas would integrate seamlessly into existing petrochemical streams. Such efforts to develop market pull could help address the problem of attracting capital to this area.
In terms of skills needed, the breakout group said the main deficit in training in its opinion was the lack of interdisciplinary coursework and collaboration among engineering, chemistry, biology, and plant science investigators. Some breakout group members also noted they would like to see a greater emphasis in chemical engineering education on using carbon from biomass as opposed to just from petroleum.
Addressing the transportation infrastructure issue, the breakout group noted that there are far more questions than answers concerning how to best move biomass into a processing system and then move the direct products of biomass conversion into the secondary processing stream. Many members of the breakout group concurred that they would like to see the emphasis on using existing infrastructure and trying to make products that can be fit into today’s infrastructure at as early a point as possible.