Biodiesel, which is a new, renewable and biological origin alternative diesel fuel, has been receiving more attention all over the world due to the energy needs and environmental consciousness. Biodiesel is usually produced from food-grade vegetable oils using transesterification process. Using food-grade vegetable oils is not economically feasible since they are more expensive than diesel fuel. Therefore, it is said that the main obstacle for commercialization of biodiesel is its high cost. Waste cooking oils, restaurant greases, soapstocks and animal fats are potential feedstocks for biodiesel production to lower the cost of biodiesel. However, to produce fuel-grade biodiesel, the characteristics of feedstock are very important during the initial research and production stage since the fuel properties mainly depend on the feedstock properties. This review paper presents both biodiesel productions from various feedstocks and their effects on the fuel properties.

In this study, biodiesels were produced from sunflower, corn, soybean, rapeseed, hazelnut, and cottonseed oils by transesterification reactions using methanol, ethanol, 2-propanol, and 1-butanol as alcohol. Potassium hydroxide, sodium hydroxide, and sulfuric acid were used as catalysts. After biodiesel production, ester conversion rates and fuel properties such as viscosity, density, and total and free glycerol were determined and compared in graphical forms. From the experimental results, it was concluded that the most suitable alcohol for biodiesel production is methanol. Other alcohols should be used with an acid catalyst in long reaction times such as at least 48 h. As the alkaline catalyst, potassium hydroxide is more superior to sodium hydroxide. Among the studied vegetable oils, sunflower oil gave the best results, while cottonseed oil gave the worst ones in terms of practicality and some fuel properties.

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