• Flexible economic and engineering models capable of evaluating the wide variety of proposed approaches for alternative fuel facilities and supply chains. Current economic and engineering models were developed with assumptions that do not match those for alternative fuels. Alternative fuel feedstocks vary widely in composition, may only be regionally and seasonally available, require evaluation of life-cycle costs and impacts, and so on.

  Models are required that can evaluate a variety of proposals, properly weigh the benefits of small-scale and distributed activities and collect and synergize the research knowledge base and make it available for analysis.

• Detailed analyses of fuel chemistry effects on fuel properties to enhance specification development for alternative fuels with unusual chemical compositions (e.g.., those composed of a single or a few molecules), and development of cost effective tests for the suitability of an alternative fuel.

  Current methods of qualifying aviation fuels involve specifications targeted at fuels derived from petroleum distillates and detailed, laborious testing of fuel suitability to ensure safety. However, there is almost no detailed understanding of how the actual chemical components of a fuel influence performance and safety, making it impossible to predict a priori what the potential issues are with a novel fuel, and full-scale testing is costly and requires tens to hundreds of thousands of gallons of fuel to complete.

  Approaches are being worked to make the specifications chemistry-based, to reduce the time and amount of fuel required for testing, and to be able to predict with confidence the impact of fuel type on operation and safety. These efforts need to be accelerated.

Identified R&D with near- and mid-term return on investment are:

• Feedstocks and processes to reduce the cost of hydrotreated esters and fatty acids (HEFA). HEFA are already qualified to be used as aviation fuel. The greatest challenge associated with this process is the cost of the final fuel, which is heavily affected by feedstock production costs. Current and proposed feedstocks can be developed to produce more oils with less land and cost, and higher crop yields. Downstream, conversion processes can be developed or modified to take advantage of lower quality oils, thus allowing use of a greater variety of oils. Investments in these areas yield immediate returns.

• Studies on relative economics of competing uses of biomass resources. Allocation of biomass resources to alternative jet fuels as opposed to other uses will be determined based on societal choices about priorities as well as relative economics of different uses of biomass. Understanding the relative economic performance of bio-based alternative jet fuels is critical to predicting their availability and success in the marketplace.

  Currently there is little information available about the relative economics and potential synergies among uses. Techno-economic analyses addressing competition and synergies among biomass-based products can be performed immediately with existing techniques, but must be based on transparent, verifiable data and/or assumptions. Rather than answering the question of how something can be done, these studies would answer the question of whether particular pathways should be pursued.

• Development and streamlining of crosscutting technologies applicable to a variety of feedstocks and processes. A key challenge to alternative fuels is the diversity of feedstocks and processes required due to regional and seasonal availability. Some technologies can be common to many processes, such as collection, concentration, dewatering, small scale operation, and so on. Identifying and investing in these enabling technologies can bring significant benefits to the whole industry.

• Feedstock production systems that incorporate diversity to enhance resilience to environmental variability and stresses such as drought. Diversification of crops, within field (concurrently or in rotation) and/or regionally can enhance the stability and reliability of feedstock supply, because some species will be more resilient to certain conditions than others, and therefore a mix is likely to be more stable than monoculture.

  Identifying suitable crop rotation schemes, species assemblages, and optimal regional diversity levels can aid in developing a robust supply chain for alternative fuel production in the face of increasing weather variability. Additional research is needed on diversification of algal cultures to address invasion by pathogens and predators leading to “pond crash,” or the collapse of the algal culture, which interrupts supply and causes costly cleaning and restart.

• Technologies to address barriers to the use of municipal solid waste and sewage sludge as feedstocks for alternative fuels. Municipal solid waste and sewage are waste products that are produced at massive scale. Currently, it costs money to dispose of or treat these wastes, but the use of wastes as feedstocks for alternative fuels may solve multiple problems of scale, cost, and waste disposal issues. Technologies are needed to facilitate separation, extraction efficiency, and conversion efficiency of such heterogeneous waste materials as feedstocks.

The direct collection and conversion of atmospheric CO₂ to fuels was identified as a high-benefit, low-readiness level process requiring sustained R&D. Key tests and trials should be funded for promising ideas, prizes should be awarded to encourage innovation, research should be fostered in the universities and government laboratories, thus seeking the approaches with high pay-off potential, the team concluded.

New tools. Separately, the CAAFI Environment team released two new tools for promoting the development and deployment of environmentally beneficial alternative jet fuels.

The Environmental Sustainability Overview provides background on what environmental sustainability is, how it is measured, mechanisms for doing so, and key environmental aspects for which sustainability may need to be demonstrated. The document is intended to provide common ground for alternative jet fuel producers and purchasers to discuss environmental performance and sustainability.

The Environmental Progression is a Readiness Tool intended to complement the Fuel and Feedstock Readiness tools already developed by CAAFI. This new Environmental Progression provides guidance on when different environmental analyses might best be performed during the development of a new fuel production process, with each level of progress indicating that environmental due diligence has been performed. This tool does not prescribe any specific sustainability methodologies or require any specific outcomes to move from one level to the next, but rather identifies whether supporting environmental analyses are being performed as the fuel or feedstock development progresses.

Both of these new tools will complement the existing CAAFI Fuel Readiness tools, including the Path to Alternative Jet Fuel Readiness, the Fuel Readiness Level and FRL Exit Criteria, the Feedstock Readiness Level, and the recently unveiled Guidance for Selling Alternative Fuels to Airlines.