Conversion of waste cooking oil (WCO) and palm fatty acid distillate (PFAD) to biodiesel

Abstract

The search for alternative fuels to substitute for fossil fuels with competitive price range is an ongoing subject for research. There are several proposed feedstock, namely refined palm oil, crude palm oil, waste cooking oil and currently, palm fatty acid distillate. Refined and crude oils were debatable to be used as the main uses for both oils were for edible purposes. Waste cooking oil (WCO) is the cheapest source and can reduce problems on waste oil disposal whereas palm fatty acid distillate (PFAD) is a byproduct from palm oil refining, therefore can be a readily available feedstock. However, due to the high free fatty acids (FFAs) content of waste and palm fatty acid distillate, these sources cannot be converted directly to biodiesel via alkaline transesterification. In this study, two step process, which combined acidic and alkaline process were used to convert waste cooking oil and palm fatty acid distillate to biodiesel. The parameter investigated was the catalyst percentage, which was varied from 1 wt% to 5 wt%. For waste cooking oil, the yield of methyl esters was constant after using 4 wt% of catalyst, with the highest yield of 90 wt%. For palm fatty acid distillate, the yield of methyl esters was also constant from 1 wt% of catalyst, thus this amount of catalyst was already sufficient to produce a high yield of methyl ester, which was as high as 95 wt%. The methyl ester composition for both sources composed mainly of stearate and palmitate. The amount of palmitate increased whereas stearate decreased with increasing amount of catalyst used.