In their perspective paper, Future transportation fuels, Gautam Kalghatgi, Howard Levinsky, and Med Colket address the challenges faced by the combustion community as they progress toward a low-carbon transportation future. The overall challenge is how to achieve significant emissions reduction while maintaining the fitness for purpose of the engines used in different transportation sectors.

Current industry and policy initiatives are aimed at incorporating fuels derived from biomass and shifting land-based propulsion systems towards gasoline/plug-in hybrids, pure battery electric vehicles and fuel-cell systems using hydrogen. Despite these initiatives for alternative fuels and propulsion systems, projections to 2050 expect the role of petroleum fuels for transportation to still be large worldwide. Therefore, the combustion community has a continuing opportunity to play a major role in reducing the emissions of GHG. While advanced combustion cycles and system changes such as lighter vehicles and electric hybridization could reduce overall fuel consumption, for heavy duty vehicles and ships, major improvements must come from engine efficiency in fuel utilization. There must also be substantial development and usage of biofuel alternatives, additional fuels derived using hydrogen from renewable power, and the ability to burn such fuels efficiently.

Spark-ignited engines may also benefit from new and improved fuel formulations. Gas-to-liquid fuels could provide a suitable solution but need to be generated from biomass rather than natural gas. Future models of hybrid (fuel/electric) power-trains will need to utilize new/better combustion systems matched with sustainable fuels.

In addition to assuring the fitness of purpose of new fuels, a number of safety, risk, and implementation factors must be addressed. These include the storing and transportation of fuels which may require significant technological remediation and societal acceptance of the non-traditional methods.

The authors of the perspective paper identify four challenges for the implementation of new fuels: Fuels tailored to engines with cycle and system advances that increase overall conversion of chemical energy to useful work, renewable fuels that are chemically converted to equivalent petroleum products matched to the combustion engine that optimizes performance, fuels that optimize the complex interactions of physical and chemical properties, and jet aircraft fuels with more stringent requirements and specific characteristics to maximize cycle efficiency. They concluded that major advances in combustion science in the past decades have provided understanding and tools that can address these challenges, and that alternative (renewable) fuels and high-performance combustion concepts/engines using fuels adapted for that purpose can reduce the environmental footprint of combustion-based transportation. To learn more, read the full perspective paper: Kalghatgi, G., Levinsky, H., & Colket, M. (2018). Future transportation fuels. Progress in Energy and Combustion Science, 69, 103-105.