Biodiesel fuel production from brown grease produced by wastewater treatment plant: Optimization of acid catalyzed reaction conditions

Periodic spikes in crude oil prices have led to a need in alternative energy sources. A major potential source of biodiesel feedstocks is brown grease, a byproduct of wastewater treatment. A recent brown grease sample from this contained 60 % FOG (fats, oils, and greases), 25 % water, and 15 % biosolids by mass. This study is focused optimizing the reaction conditions (i.e., quantities of Methanol, Sulfuric Acid, Fe-2(SO4)(3), and time) to maximize the yield of esters, with minimal residual free fatty acid (FFA), in the shortest residence time. Response Surface Methodology (RSM) was used to evaluate the correlation between the process variable and the response. The significance of quadratic model of each response was determined by analysis of variance, where all models indicated sufficient significance with p-value < 0.0001. Using a basis of 40 g brown grease, optimized conditions were 35 ml MeOH, 1.3 ml H2SO4, 0g Fe-2(SO4)(3) and reaction time of 120 min, resulting in a biodiesel yield of 99.70 %. The results showed efficient biodiesel production under the optimum conditions.