Malaysia produces great quantities of waste lignocellulosic biomass every year from oil palm cultivation. Palm wastes are not currently utilised in a very productive manner because the relatively low price of petroleum-derived fuel has prevented biomass-derived fuel from gaining market share. It is envisaged that taking into account environmental sustainability in addition to cost in the evaluation of the viability of a fuel will make biomass-derived fuels more feasible for adoption compared to the conventional fossil fuels. The environmental sustainability metric Sustainable Process Index (SPI) is applied to several competing lignocellulosic biomass pretreatment methods, namely ozonolysis, ionic liquid treatment, and ammonia fibre expansion (AFEX). These methods are chosen because of the relatively novel processes, which are not commonly used at industrial scale. Existing studies have shown that these processes present possible improvement over conventional methods. Using the SPI methodology, it is determined that the total specific service area, atot, for AFEX is the lowest, the most environmentally sustainable process for the pretreatment of palm lignocellulosic biomass, followed by ozonolysis and then ionic liquid treatment.