Analysis on the biodiesel production using grease trap oils from restaurants

A large amount of waste cooking oils, animal fats and grease trap oils is generated from restaurants, food processing industries and fast food shops all over the world. The disposal of these waste oils induces a heavy burden on the municipal wastewater treatment and landfill facilities. It is therefore economical and environmentally beneficial if these waste oils can be recycled. Using them as a feedstock for biodiesel production can not only reduce the amount of waste oils being treated, but also significantly lower the cost of biodiesel compared with that produced from high-quality edible oils. This study was initiated to investigate the potential of using grease trap oils from restaurant as a feedstock to produce biodiesel. Experimental results indicated high feasibility of such production, but the production yield would be affected by several factors. Reaction time was found to be a controlling factor of biodiesel yield, while catalyst concentration had a larger effect on the percentage of esters in products and ester yield than reaction time and methanol/oil ratio. Enhancing the ratio of methanol to raw oil markedly increased the biodiesel yield, but produced lesser effect on the purity level of biodiesel. The viscosity was substantially reduced from 48 cSt of raw oils to 4 cSt of biodiesel