Sustainable Biodiesel Production from Turkish Coffee Waste Oil: A Comparative Study with Homogeneous and Heterogeneous Catalysts

Biodiesel is a renewable fuel obtained from vegetable or animal oils and a good alternative to fossil fuels. Since the raw material cost constitutes much of the total biodiesel production cost, cheaper waste oils are potential substitutes for vegetable oils in biodiesel production. Coffee is the product with the second-highest trade volume in the world after oil, at approximately 1.5–2 million tons annually, and results in a huge amount of waste. Recycling such waste into fuels is a promising way to solve the waste problem and this waste is potential raw material for biodiesel production. In this study, biodiesel was produced from the oil extracted from Turkish coffee waste, which has approximately 10–15% oil. The molar ratio of methanol to Turkish coffee waste oil (12, 15, 20), catalyst concentration (1, 1.5, 2 wt.%), and time (60, 120 min.) were the studied parameters. Potassium hydroxide and ion exchange resin were used as catalysts in the experiments. The highest biodiesel yield was obtained with potassium hydroxide catalyst, while the results obtained by using ion exchange resin may be improved. After the parametric study was completed for biodiesel production, the physical and chemical properties of the produced biodiesel were compared with the international biodiesel standards. The values of properties were at an acceptable level and are suitable for improvement.