The conversion of lignocellulosic biomass to liquid fuels presents an alternative to the current production of renewable fuels for IC engines from food crops. However, realising the potential for reductions in net CO2 emissions through the utilisation of, for example, waste biomass for sustainable fuel production requires that energy and resource inputs into such processes be minimised. This work therefore investigates the combustion and emission characteristics of five intermediate platform molecules potentially derived from lignocellulosic biomass: gamma-valerolactone (GVL), methyl valerate, furfuryl alcohol, furfural and 2-methyltetrahydrofuran (MTHF).
The study was conducted on a naturally aspirated, water cooled, single cylinder spark-ignition engine. Each of the platform molecules were blended with reference fossil gasoline at 20 % wt/wt. The experiments were performed at constant engine speed (1200 rpm), with the throttle position and fuel flowrate being adjusted for every test to maintain a constant engine load and equivalence ratio (0.95-0.98). Knock limits were determined for each test fuel blend by advancing the spark timing, and heat release rates were analysed to investigate the impact of the platform molecules on flame propagation speeds. The lowest and highest knock limit were exhibited by furfural and furfuryl alcohol blends, respectively. Emissions of NOx, CO, particulate mass and total particle number exhaust emissions showed a greater sensitivity to engine air fuel equivalence ratio than properties of the platform molecules tested as blends. The particulates from the furfural blend had peak particle diameters of 40 nm, while those from furfural alcohol had a peak particle diameter of 80 nm.