Effect of a glycerol-derived advanced biofuel –FAGE (fatty acid formal glycerol ester)– on the emissions of a diesel engine tested under the New European Driving Cycle

Abstract

A new advanced biofuel –FAGE (fatty acid formal glycerol ester)– produced from crude glycerol has been blended with diesel fuel (20% FAGE content) and tested in an automotive engine following the New European Driving Cycle. Since cold flow properties, volatility and viscosity are the critical properties of this biofuel, the driving cycles were performed from both warm and cold starts. The FAGE blend showed significant benefits in hydrocarbon, carbon monoxide and particle emissions, particle number and opacity when the cycle was started from warm conditions. Such benefits were even more important during the extra-urban period, where also small engine efficiency benefits were found. Differently, the mentioned emissions increased substantially with respect to those of diesel during the first urban sub-cycle at cold start. Among the emitted hydrocarbons, the non-oxygenated ones were more sensible to the engine temperature. Also, the nucleation mode in the particle size distributions increased at cold conditions. NOx emissions were slightly increased with the FAGE blend during the extra-urban sub-cycle, and differences in the NO2/NO ratio were found during the initial urban sub-cycle from cold start. The results have been explained based mainly on the injection timings, the fuel–air ratio, the oxidation catalyst performance and the fuel properties.