Biodiesel production from waste lard using supercritical methanol

In this study, transesterification of refined lard in supercritical methanol with no pre-treatment was performed in a temperature range of 320–350 °C, molar ratios of methanol to oil from 30 to 60, pressures from 15 to 25 MPa, reaction times from 5 to 20 min, and agitation speeds of 0–1000 rpm. The effects of reaction parameters were investigated to determine the optimum reaction conditions. The highest content of fatty acid methyl esters (FAMEs) from refined lard was 89.91%, which was obtained at a temperature of 335 °C, a molar ratio of methanol to oil of 45, a pressure of 20 MPa, a reaction time of 15 min, and an agitation speed of 500 rpm. Biodiesel production from waste lard under the optimal reaction conditions was also carried out to validate the use of waste lard as a feedstock. Even though waste lard samples contain various free fatty acids and water contents, FAME contents from waste lard with no pre-treatment were found to be comparable with those from refined lard. From this result, it is concluded that waste lard can be utilized as an alternative feedstock for biodiesel production using a supercritical process, thus replacing the high-cost refined vegetable oil feedstock.

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► Waste lard was converted to biodiesel via one-step supercritical transesterification.
► The highest FAMEs content from refined lard was 89.91%.
► Compared to FAMEs contents from refined lard, those from waste lard were comparable.
► Waste lard can be utilized as a promising alternative feedstock for supercritical process.