The cost of biodiesel production can be reduced by a number of strategies such as utilization of waste cooking oils and non-edible plant oils as well as implementation of improved separation technologies. In addition, processes dealing with the glycerol by-product can have economic benefits. In the present study, acidification of crude glycerol with phosphoric acid to pH 9.67 followed by acidification to 4.67 was implemented to produce high quality potassium phosphate during glycerol purification. KH2PO4, K2HPO4, glycerol and free fatty acids (FFAs) with a purity of 98%, 98.05%, 96.08% and 99.58% were obtained, respectively. (C) 2011 Elsevier Ltd. All rights reserved.