Spent Coffee Ground (SCG) was studied as a potential source of oil feedstock for biodiesel production as an alternative waste utilization instead of disposed of as municipal waste. This study using microwave-assisted extraction (MAE). The optimal condition of MAE obtains of n-hexane (4v/v) as extraction solvent, microwave power 460 W, solvent to the material ratio eight mL/g, extraction temperature 72℃, and time 42 min. The oil yield of 24.70 % reaches under optimum conditions. Free fatty acids (FFA) of the extracted oil are converted into fatty acid methyl ester (FAME) by base-catalysed esterification. The study investigates the effect of temperature, FFA ratio to methanol-CaO solution, and reaction time either.  With one step alkali-catalysed transesterification, oil conversion to methyl ester can be enhanced from approx. 42–75% by increasing the reaction time, the reaction temperature, and the Methanol-CaO/FFA ratio. However, a complete oil conversion can only achieve by utilizing a two-steps transesterification process. The results showed that 4.4 L of biodiesel was produced from 1 kg of spent coffee ground. As such, this study expected this study to lead to the paradigm shift in spent coffee ground management with the ultimate target of zero-solid discharge highlights.

Keywords: Spent coffee ground, microwaved extraction, coffee oil, biodiesel.