Biodiesel production from municipal waste using lipase catalysis

Abstract

As biocrude exhibits inferior properties for it to be used as a high-value fuel, upgrading is needed. Thermochemical upgrading methods prove to be the most successful in terms of oxygen removal and stabilisation of biocrude; however, heavy organics in biocrude have the tendency to polymerise upon thermal treatment. This results in catalyst deactivation and coking during hydrotreatment of biocrude. Chemical upgrading, such as conventional esterification at mild reaction conditions, is also ineffective as the esterification reaction is incomplete due to the carboxylic acid-water equilibrium reaction. In this study, the enzymatic upgrading route was evaluated by studying the conversion of fatty acids to methyl esters in the biocrude. A fatty acid conversion of 94.6 mass % at 30 ֯C was obtained, showing that moisture and other components present in biocrude do not have a negative effect on fatty acid esterification using lipase catalysis. The difference in oil-to-oil molar ratio between 1:2 and 1:18 is not significant due to the presence of hydroxyl groups in the oil which contributes to the esterification reaction. No heavy fraction formation was observed in the boiling curves which is an indication that no significant coking occurred. Although the fuel value of the produced biodiesel at 34.9 MJ/kg is lower than that of petroleum fuel, the biodiesel in this study can be used in blends for heating, cooking and electricity generation applications.