Low carbon transportation fuels: deployment pathways, opportunities and challenges

Low carbon fuels are transport energy carriers with a lower greenhouse gas footprint than existing fuels on a lifecycle basis. Although some low carbon fuels could be blended with existing fuels - making them practical options to reduce GHG emissions in the short-term - others may require new vehicles and infrastructure, limiting their short-term impact on emissions. In this study, we assess three deployment pathways for low carbon fuels in combination with a range of vehicle, vessel and aircraft efficiency improvements. The deployment pathways include: (1) refinery reformulated drop-in fuels compatible with existing fuel standards; (2) blended drop-in fuels compatible with existing fuel standards, and non-drop-in blended fuels that fall outside existing fuel standards; and (3) alternative fuels with fundamentally different supply chains that require new vehicles, vessels and aircraft to be purchased, many of which would be dedicated to the use of the alternative fuel ( e.g. , hydrogen, ammonia or methanol). Some low carbon fuels are shown to have relatively modest barriers to widespread deployment, but others require more substantial changes to achieve deep levels of decarbonization. Major challenges include establishing and scaling supply chains, revising fuel standards that directly or indirectly restrict the use of some low carbon fuels, and accelerating the pace of infrastructure deployment and adoption of new vehicles, vessels and aircraft by the market. Low carbon fuels can play a role in decarbonizing the transport sector, but the greenhouse gas impact depends on the chosen pathway. A range of fuel options for the on-road, marine and aviation sectors are assessed on a well-to-wheel or -wake basis.