Utilization of oil recovered from biodiesel wastewater as an alternative feedstock for biodiesel production

Abstract Biodiesel is a renewable fuel commonly used to replace diesel. Currently, biodiesel production is controversial in food security circles because edible oils are used as biodiesel feedstock. This study investigates the use of nonedible oil, recovered from biodiesel wastewater (BWW), as an alternative feedstock for biodiesel production. BWW was treated with acidification with H2SO4 to recover the oil phase from the water. The major components of the recovered oil, 56.9 wt% ester and 38.1 wt% free fatty acids (FFA), demonstrated its potential as a feedstock for biodiesel production by esterification. The optimal conditions for biodiesel production from the recovered oil were 5 wt% H2SO4, a 2:1 M ratio of ethanol to FFA, a reaction temperature of 70°C, and a reaction time of 120 min. These conditions produced biodiesel with a purity of 97.7 wt% and a yield of 98.5 wt%. Additionally, the oil recovery process greatly reduced the pollutant load in BWW, bringing the cost of treatment below the usual cost of treating BWW with a high content of organic matter.