Biodiesel mainly animal and vegetable fats and oils, is now the most studied vegetable fats, vegetable fats soybean oil, rapeseed oil, palm oil-based. Currently biodiesel is mainly used to produce chemical and ester method, which uses a chemical method and other animal or vegetable fats and oils with lower alcohols methanol esterification reaction at an acid or alkaline catalyst and a high temperature to produce the corresponding fatty acid methyl ester, washed drying biodiesel can be obtained. Methanol can be recycled in the production process, the production process can produce about 10% of the byproduct glycerol. Enzymatic which uses animal and plant oils and low-carbon alcohol by lipase transesterification, fatty acid methyl ester to prepare the corresponding. Enzymatic synthesis of biodiesel have mild conditions, with less alcohol, pollution emissions and other advantages. But now the main problem is the presence of enzymatic synthesis of methanol conversion rate is low, generally only 40-60%. Due to the current long-chain fatty alcohols lipase esterification or transesterification, but not on a short chain fatty alcohol conversion rate, and short-chain alcohols have a certain toxicity of the enzyme, the enzyme's short life, byproduct glycerin and water are difficult to recycle not only suppress product formation, but also on the immobilized enzyme toxic glycerin, shortening the life of the immobilized enzyme.
The main problem is the high cost of biodiesel, according to statistics, 75% of the production cost of bio-diesel raw material costs. Therefore, the use of cheap raw materials and improve the conversion rate is the key to reducing the cost of biodiesel can industrialization. The United States has begun to study by genetic engineering methods with high oil oil crops; Japanese use of industrial waste oil and waste frying oil; Europe is not suitable for growing food in the oil-rich land to grow crops. Thus the development of technology, biodiesel will become an important low-cost renewable energy.