Mono-alkyl esters (biodiesel) production from wastewater sludge by esterification

To realize higher yields of mono-alkyl esters (Biodiesel) without sacrificing the environment and food sources; various researchers have considered utilizing different waste materials. In this work lipid extraction and their conversion into esters from wastewater sludge was investigated using a mixture of polar and non-polar solvents, methanol and homogeneous sulfuric acid catalyst. The effect of solvent extraction time, concentration of acidic catalyst used and the esterification reaction time to produce esters is reported for ex-situ two step and in-situ one step method. The whole experimental work of ex-situ/in-situ extraction and esterification was performed at a temperature of 100 degrees C and mixing rate of 100 rpm. Solvent extraction yield of lipids increased from 34 to 53% in two to six hours of solvent extraction. It was found that acidic catalyst concentration in the esterification mixture and esterification reaction time both have a major impact on esters yield. A highest ester yield of 78% was noted in the ex-situ two step method with two hours of esterification of filtered lipids and a 55% ester yield was noted in the in-situ one step method after six hours of simultaneous extraction and esterification in the same reactor respectively.