Vehicle manufacturers are facing increasing legislative pressure to reduce vehicle emissions and achieve zero tailpipe CO2 emissions within the coming decade. The focus on techniques to reduce the tailpipe CO2 emissions, rather than vehicle lifecycle emissions, naturally dictates electrified solutions. However, this will not address the increased emissions resulting from vehicle manufacture, the emissions of the legacy fleet, or enable niche or classic applications, to be decarbonised for future use. The use of bio-derived fuels, and fully synthetic fuels, can provide a technical solution to these challenges, but it is beneficial if these can be used as a drop-in replacement to existing fossil derived fuels, as this would enable straight-forward backward compatibility with existing vehicles and avoid the need to re-engineer future engine designs or upgrade existing hardware.
The present study investigates the use of 100% bio-derived fuel in a spark-ignited internal combustion engine from the passenger car sector. The biofuels tested have been engineered to provide the characteristics of fossil-derived gasoline but being derived from a 2nd generation bio-feedstock, enable significant well-to-wheel and vehicle lifecycle CO2 savings. Detailed combustion data is presented to demonstrate the characteristics of these bio-gasoline fuels relative to a fossil-derived baseline. Both raw engine-out emissions and after-treated emissions are investigated. All currently legislated emissions are assessed, as well as tailpipe CO2 emissions, over steady-state and transient cycles. The work reported in this paper was carried out using both engine-dynamometer and vehicle testing to enable detailed analysis of the combustion behaviour as well as to study the overall suitability of the bio-fuels.