Catalyst-free fatty acid methyl ester production from wet activated sludge under subcritical water and methanol condition

► Wet activated sludge can be directly converted into biodiesel by in situ methanolysis under subcritical condition. No drying pre-treatment steps are necessary. ► High conversion of FAME can be achieved by using this method. ► The process is very simple and conventional catalyst such as KOH and H2SO4 is not required.