Analysis and identification of gaps in research for the production of second-generation liquid transportation biofuels: IEA Bioenergy: T41(2): 2008:01

Project 2 was initiated on 13 January 2006 based on a proposal by Larry Russo (Office of Biomass Program, US Department of Energy) to the IEA Bioenergy Executive Committee. Dr Michael Ladisch (Laboratory of Renewable Resources Engineering, Purdue University) joined as the Project Co-Leader. A statement of work was then finalised and submitted for approval by the Executive Committee with a start date of June 1, 2006. The project co-leaders worked with a team of participants from Finland, the Netherlands, Sweden, UK, USA, and the European Commission to develop a global view of gaps in research for addressing production of second-generation liquid biofuels. The Project 2 team developed its findings based on inputs from participating countries through a series of conference calls, published reports, and discussion and review with experts who are carrying out work associated with related Tasks within IEA Bioenergy. Research gaps were found in cellulosic ethanol, Fischer-Tropsch liquids and green diesel, dimethyl ether and P-Series fuels. Lignocellulosic ethanol is derived from pre-treatment, hydrolysis, and fermentation of the resulting sugars from cellulosic sources such as wood chips, agricultural residues, and grasses. Green diesel is a high boiling component, not derived from vegetable oil, obtained either from Fischer-Tropsch synthesis or through pyrolysis of biomass. Dimethyl ether has potential as a high quality fuel for diesel engines and is produced by converting syngas into methanol followed by dehydration of methanol to dimethyl ether. P-Series fuel is a mixture of ethanol, methyltetrahydrofuran, pentanes and higher alkanes, and butane. Methyltetrahydrofuran may be produced from dehydration of pentose and glucose sugars to form furfural and levulinic acid respectively, which when hydrogenated result in methyltetrahydrofuran. Common denominators in gaps for these different fuels and the biochemical or thermochemical processes used to produce them are given by three main areas. These are: o catalysts and biocatalysts; o feedstock preparation and bioprocessing; and o systems integration. In the biocatalyst (or catalyst) area research is needed to achieve more robust, versatile, and cost-effective catalysts. The catalytic systems must be less subject to inhibition and more stable in the presence of chemically complex feedstocks derived from biomass materials. With bioprocessing, the gaps lie in economic enzyme production, reduction of enzyme inhibition, development of pentose utilising and cellulase producing micro-organisms, feedstock preparation (pre-treatment), and inhibitor removal. For thermochemical systems, the list is analogous except the term 'catalyst' replaces 'enzyme' or 'microorganism'. Gaps were identified in feedstock preparation, with this term being broadly defined. Feedstocks are defined as biomass materials entering the process, as well as gases derived from biomass and used for catalytic formation of diesel or other fuels. Pre-treatment of cellulosic materials so that they are more efficiently converted to fermentable sugars is one form of feedstock preparation, and research that addresses the fundamental science and process development of pre-treatments should be viewed as a research gap. Clean-up of gases derived from biomass before the gases enter a catalytic step is another important research gap. Both areas impact on the efficiency, longevity, and cost of biocatalysts and catalysts. Systems integration and the integration of bioengineering with chemical engineering for cost-effective production and use of second-generation fuels represents a third research gap. This area encompasses gaps that must be addressed in better understanding the infrastructure required to deliver second-generation fuels and policies that would accelerate their introduction to the market place.