Raw material is the key to produce biodiesel. In the process of preparing biodiesel, raw material cost accounts for more than 70% of the total cost. Therefore, in the process of preparing biodiesel, searching for large-scale, low-cost, pollution-free and high-utilization raw oil is the core and key problem to be solved in the industrialization of biodiesel. Many countries in the world choose suitable raw materials to produce biodiesel according to their national conditions. Because high-yield genetically modified soybean is widely planted in the United States, soybean oil is used as the raw material for biodiesel production. South-East Asia is suitable for planting oil palm according to local soil climate. So palm oil is used to develop biodiesel industry: European countries use rapeseed oil in edible oil to produce biodiesel. Especially in Germany, rapeseed is widely planted. Japan mainly uses cheaper waste cooking oil to produce biodiesel. China has a vast territory, vast territory and abundant raw materials for biodiesel production. It is of great significance to study the advantages and disadvantages of preparing biodiesel from different raw materials in order to find the superior raw materials for biodiesel production. The main raw materials for biodiesel production are vegetable oils (herbal oils and woody oils), animal oils, microbial oils and waste useless oils.
(1) Vegetable oils and fats
Vegetable oils include soybean oil, peanut oil, rapeseed oil, sesame oil, corn oil, cottonseed oil and other herbal oil crops. They also include Jatropha curcas, Coptis chinensis, tallow tree, palm oil and other woody oil crops. They are one of the most ideal raw materials for biodiesel production.
- Soybean oil
Large-scale cultivation of high-yielding GM soybeans in the United States has become the largest producer of soybeans. More than 55% of domestic biodiesel uses soybeans as raw materials, Brazil and Argentina as baits for the second and third producers of soybeans. The biodiesel production in both countries started relatively late. There is no report that China, as the fourth producer of soybeans, has a large population. It has not been able to meet people’s food needs. Moreover, there is a land contention between soybean and grain, so the potential of increasing planting scale is limited. The amount of soybean oil extracted from soybean seeds is 1% of the quality of soybean oil in NaOH. The ratio of oil to alcohol is 1:6, the reaction temperature is 65 C, and the stirring time is 30 min. The biodiesel obtained can reach the standard of 0# diesel oil III.
- Rapeseed oil
Rapeseed oil as the main raw material for biodiesel production in European countries also has great development potential as biodiesel raw material in China, especially its unique advantages: 1) the chemical composition of rapeseed oil is very similar to diesel oil; 2) rapeseed cultivation has a wide range of adaptability; there is no land competition with major grain; 3) it can increase the fertility of cultivated land and the yield of subsequent crops.
- Cottonseed oil
As the largest producer of cotton, China has huge cottonseed resources. However, due to the low technology level of oil extraction and the low oil yield, there are still a large number of cottonseed without oil extraction. At the same time, the proportion of consumption of cottonseed oil as edible oil is also declining. Therefore, cottonseed oil as a raw material for biodiesel production has great development potential in the future.
- Jatropha curcas
Jatropha curcas L. is widely distributed in Yunnan, Sichuan and other places. Its seed oil content can reach up to 60%. The content of oleic acid and linoleic acid is high (up to 38%-40%) and almost does not contain more than C20 fatty acid. It has good blending with diesel oil, gasoline and alcohol. It is an ideal biodiesel raw material to use Jatropha curcas oil as raw material. Chemical preparation of biodiesel mainly depends on catalysis. Chemicals or specific reaction media change the molecular structure of Jatropha curcas oil. Finally, single-chain fatty acid methyl ester Li Hua was formed. The biological properties, physicochemical properties and fatty acid composition of Jatropha curcas seeds in six regions of Southwest China were analyzed and compared. The results showed that these characteristics were optimized by different regions. Weiyajie studied the optimum conditions for transesterification of Jatropha curcas oil with methanol under the action of NaOH catalyst. Yongkaidong uses hot pressed Jatropha curcas fruit oil as raw material. Biodiesel was prepared by liquid alkali ester exchange method. The best degumming, deacidification and ester exchange reaction conditions were successfully developed. Zhang Guowu analyzed the bottlenecks restricting the industrialization of Jatropha curcas in China and put forward the corresponding development countermeasures.
- Pistacia chinensis Bunge
The oil content of seeds of Pistacia chinensis is about 25%. The carbon chain length of biodiesel produced mainly from Pistacia chinensis oil in Jianghuai area is between C17 and C20. Its physical and chemical properties are very close to that of ordinary diesel. At present, the biodiesel produced by using Coptis chinensis oil as raw material has met the American biodiesel standard Wang Jun IV. After investigating the resources of biodiesel raw material tree species in Ankang City, we found that Coptis chinensis as a native tree species can be used as one of the species for biodiesel production. It has great development potential. Huangdao? I et al. studied the cultivation and industrialization of Coptis chinensis in Anhui Province as an energy forest.
(2) Animal fat
Animal oil is rich in sources, mainly from animal slaughter, waste animal fur treatment and edible meat residue oil, including lard, butter, lamb oil and fish oil. The United States, Europe and Japan have begun to use animal fats to produce biodiesel. The proportion of animal husbandry and animal husbandry in China is very small. It needs a lot of imports. So it is impossible for animal fats to become the main raw material for biodiesel development. There is almost no way for animal fats to prepare biodiesel in China. Animal fats can be used as a supplementary resource in the production of biodiesel in China. Domestic biodiesel production from animal fat includes microemulsion method, transesterification method, enzyme synthesis method, etc. Using tuna oil as raw material, biodiesel yield reached 90% by using immobilized lipase step-by-step alcoholysis process.
- Microbial grease
Most microbial oils are C16 and C18 fatty acids. Research on the production of grease by microorganisms began in the 1940s. Since the nineteen nineties of the twentieth century, microalgae, fungi, bacteria, yeast and microalgae have been found to produce many special oils and oils, and breakthroughs in microalgae oils and oils have been the subject of many recent studies. Microalgae is one of the primitive plants with the highest photosynthetic efficiency. Microalgae are rich in oil, high oil yield, do not occupy cultivated land, and can be cultured on a large scale. It is an ideal raw material for biodiesel production in China. The advantage of using engineering microalgae to produce diesel oil is that the production capacity of microalgae is high, and using seawater as natural medium can save agricultural resources, which is tens of times higher than that of terrestrial plants. Generally, the oil content of microalgae can reach 20%-50%. The oil content of some microalgae can exceed 80% of their dry weight.
- Waste useless oils and fats
Waste oils and fats mainly include waste cooking oil, waste cooking oil, waste cooking oil and fried food oil as alternative fuels. Compared with petrochemical diesel, although there are some problems such as high viscosity, poor volatility, poor mixing effect with air and easy thermal polymerization, the performance of ideal diesel oil substitutes can be fully satisfied by transesterification. Every year, millions of tons of waste oils and fats are produced from food processing, animal and plant processing. The acidified oils recovered from the crude oils processed by vegetable oils are mainly free fatty acids. Waste oils and fats are the most economical raw materials for biodiesel production, but there are many shortcomings such as limited quantity of waste oils and fats, complex components and high process requirements, so they are abandoned by many factories.