Commercial production of biodiesel uses refined vegetable as feedstock with base as a catalyst. However, pure vegetable oil contributes up to 80% of the overall biodiesel production cost. Activated sludge is a product of a biological treatment and a rich source of lipid, hence it should be a potential feedstock for biodiesel production. It was estimated that drying of wet sludge constitutes about 50% of the cost of biodiesel production from wet activated sludge. In this study, wet activated sludge was directly used as feedstock for reacting with methanol under subcritical condition in which water acted as an acid or base catalyst. At 250o C and a methanol to wet sludge ratio of 3.0 mL/g, a fatty acid methyl ester (FAME) yield of 33% could be achieved in 4 hours. Acetic acid was employed as a catalyst to improve FAME yield as well as lower the amount of methanol and reaction time. The same FAME yield (about 33%) can be obtained in 1 h when 3.0 mL of solvent mixture (10% acetic acid in methanol) was used per gram of wet sludge. This process can be applied to maximize biodiesel conversion of feedstock with high FFA and moisture contents.

In situ transesterification of wet activated sludge in subcritical conditions

248th National Meeting (2014)

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