Issues in Processing Crude Glycerol Derived from Waste Cooking Oil Transesterification

Growth in biodiesel production has led to an excess of crude glycerol and economical purification methods are desired to enhance the utility of this glycerol-rich stream. The choice of oil feedstock, the sequence of processing steps and the selection of process conditions will impact the composition of the crude glycerol produced in the biodiesel process. In this work, crude glycerol obtained from transesterification of waste cooking oil was used to study the impact of methanol content, acid identity and acid concentration on the purity, properties and recovery of the acid-treated glycerol phase. The properties of glycerol phases recovered after acidification with sulfuric or phosphoric acid showed a significant dependence on water and methanol content whereas this was not observed for glycerol phases acidified with hydrochloric or acetic acid.