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Recently introduced sulfur caps on marine fuels in so-called sulfur emission control areas (SECAs) are forcing shipping companies to sail on more or less automotive grade diesel in lieu of the considerably less expensive, but sulfur-laden heavy fuel oil (HFO) to which they were accustomed. This development is an opportunity for a bio-based substitute, given that most biomass is sulfur free by default. Moreover, given that biomass is typically solid to start with, cracking it to an HFO grade, which is highly viscous in nature, will involve fewer and/or less harsh process steps than would be the case if an automotive grade fuel were to be targeted. In this study, a renewable low sulfur heavy fuel oil (LSHFO) has been produced by means of subcritical water assisted lignin depolymerization in the presence of a short length surfactant, ethylene glycol monobutyl ether (EGBE).

Net heat release rates and knock characteristics were derived from in-cylinder pressures for different fuels in a single-cylinder engine; the effect of an ashless antiknock, N-methyl aniline (NMA) was also studied. The maximum net heat release rate (MHRR) resulting from the final high-temperature chemistry determines the knock intensity. Paraffinic fuels have similar knock intensities at comparable knock occurrence frequencies. Aromatic fuels have significantly lower MHRRs and give much lower mean knock intensities for a given knock occurrence frequency compared to paraffinic fuels. Adding NMA to a paraffinic fuel increases the spark advance required to get a chosen frequency of knock occurrence as it increases the octane number of the fuel but has little effect on MHRR and hence knock intensity.