As a renewable energy, biomass energy is the fourth largest energy consumption in the world, which is second only to coal, oil and natural gas. It occupies an important position in the whole energy system. As one of the most important renewable liquid fuels for biomass energy, biodiesel has the advantages of high energy density, good lubricity, safe storage and transportation, good explosion resistance and full combustion. It also has the advantages of renewability, environmental friendliness and good substitution. It is the most promising bulk bio-based liquid fuel. Reasonable development and utilization of biodiesel can promote the development of biodiesel. The sustainable development of national economy and environmental protection will have far-reaching significance.
Energy is the pillar of the development of human society. With the rapid development of the world economy, the demand for energy is also increasing rapidly. According to BP’s prediction, according to current production, the world’s oil reserves can only be exploited for 40 years, natural gas for 65 years and coal for 165 years. Energy shortage has become an important factor restricting the development of the world economy. Therefore, the search for renewable energy has attracted worldwide attention. As a renewable energy, biomass energy is the fourth largest energy consumption in the world, which is second only to coal, oil and natural gas. It occupies an important position in the whole energy system. Its main component is fatty acid monoalkyl esters obtained by transesterification of animal and vegetable oils (fatty acid triglycerides) and short chain alcohols (methanol or ethanol). Biodiesel is rich in raw materials, including vegetable oil (herbal vegetable oil, woody vegetable oil, aquatic vegetable oil), animal oil (lard, butter, lamb oil, fish oil) and industrial and restaurant waste oil. As one of the most important renewable liquid fuels for biomass energy, biodiesel has the advantages of high energy density, good lubricity, safe storage and transportation, good explosion resistance and full combustion. It also has the advantages of renewability, environmental friendliness and good substitution. It is the most promising bulk bio-based liquid fuel. Promoting the sustainable development of the national economy and protecting the environment will have far-reaching significance.
Biodiesel is a renewable oil resource (such as animal and vegetable oils, microbial oils and waste cooking oils), which is made by esterification or transesterification process. The main component of biodiesel is long chain fatty acid methyl ester liquid fuel [8-10]. It is known as “green diesel”. Its performance is very similar to ordinary diesel, and it is a high-quality alternative to petrochemical fuel.
Biodiesel is a kind of renewable energy which is made from vegetable oil, animal fat and other renewable oils. Animal and vegetable oils come from a wide range of sources, such as castor oil, tea oil, Tung oil, linseed oil, palm oil, rapeseed oil, cottonseed oil, olive oil, soybean oil, peanut oil, corn oil, fish oil, lard, butter, algae oil, oil foot or restaurant waste oil, which provide a wide range of raw materials for the production of biodiesel [11-12]. At present, rapeseed oil, bark tree oil, soybean oil, Jatropha oil, rice bran oil, industrial lard and butter are mainly used as raw materials.
Compared with petrochemical diesel, biodiesel has many advantages. It has good start-up performance of cryogenic engine, and can reach – 20 C without additive cold filter point; no aromatic hydrocarbon, high cetane number, combustion performance and explosion resistance are better than petroleum diesel; flash point is higher than petroleum diesel, which is not a dangerous product, and is conducive to safe transportation and storage; it has good kinematic viscosity and low sulfur content, which makes biodiesel not affected. In the case of fuel atomization, it is easier to form a layer of oil film in the cylinder, which can improve the lubricity of motor parts, reduce the wear rate of fuel injection pump, engine block and connecting rod, and prolong the service life. Oxygen content is higher than that of petroleum diesel, which can reach 10%. In the combustion process, less oxygen is needed, which can promote the ignition effect and reduce smoke exhaust. At the same time, it can be used as an additive mixed with ordinary diesel oil in any proportion, and it is also a fuel with dual effects. In addition, it is a non-toxic substance to human beings and animals, and it is environmentally friendly to use. In the exhaust gas from biodiesel combustion, the emission of toxic organic matter is only 1/10 of that of petroleum diesel, which has good biodegradability, good health and environmental protection. Compared with other alternative fuels such as compressed natural gas, dimethyl ether and hydrogen fuels, the system using biodiesel has less investment, and the original engine, refueling equipment, storage equipment and maintenance equipment need not be changed.
Development status of biodiesel at home and abroad
Development Status of Biodiesel Abroad
The research on biodiesel started in 1970 and developed rapidly in the past 15 years. Although its development history is not very long, due to its good performance, it has attracted worldwide attention. About 28 countries devote themselves to the research and production of biodiesel [19]. In order to vigorously promote the development of biodiesel industry, European and American governments have formulated a series of financial subsidies, preferential tax policies and other support. Germany, France, Italy, the United States, Canada and other countries have established a number of biodiesel production plants and began to use biodiesel on a large scale [20-21]. In biodiesel raw materials, the European Union countries use rapeseed as the main raw material, the United States and Brazil use soybean as the main raw material, and Southeast Asian countries use superior natural conditions to grow oil palm to obtain oil resources. According to the survey and investment forecast report of China’s biodiesel industry from 2009 to 2012, the annual output of biodiesel in the world reached 15.9 million tons in 2009. Among them, the production of biodiesel in European Union countries, mainly France and Germany, is about 8.7 million tons, that in the United States is about 1.5 million tons, that in Brazil is 1.2 million tons and that in Argentina is 1.1 million tons. The world biodiesel production is expected to reach more than 19 million tons in 2010.
Development status of biodiesel in China
Although the research and development of biodiesel in China started relatively late, it developed very fast, and some scientific research achievements have reached the international advanced level. The research involves the distribution, selection, breeding, genetic improvement and processing technology and equipment of oil plants. In the 1980s, the Shanghai Institute of Internal Combustion Engines and Guizhou Mountain Institute of Agricultural Machinery jointly undertook a lot of basic experimental exploration on biodiesel research and development [22]. Many scientific research institutes and universities have carried out experimental studies on the physical and chemical properties of vegetable oil, esterification process, diesel additives and combustion performance of diesel engines. At the same time, according to the chemical structure of natural oils and fats, the Chinese Academy of Forestry Sciences has studied the comprehensive preparation technology of biodiesel and high value-added chemical products, which makes the processing and utilization of biodiesel not only technically feasible, but also economically feasible. Industrialization can be achieved [23]. However, compared with foreign countries, China still has a certain gap in the development of biodiesel, and the scale of industrialization is still small. Although the development of biodiesel in China is only in its infancy, the Chinese government attaches great importance to the development of alternative fuels for petroleum, and has formulated a number of policies to promote its vigorous development. The Tenth Five-Year Plan outline defines the development of biodiesel as the direction of national industrial development. In 2004, the Ministry of Science and Technology launched the “Biofuel Oil Technology Development” project of the “Tenth Five-Year Plan” National Science and Technology Research Program. The National Development and Reform Commission also explicitly included “Key Technologies for Industrial-scale Biodiesel Production and Process Control” in “Key Technologies for Saving and Replacing Petroleum”. In the 11th Five-Year Plan, the research and development of biodiesel and other biomass energy sources will also be the first [24]. At present, the research and development of biodiesel in China has also made some significant achievements.
Hainan Zhenghe, Sichuan Gushan and Fujian Excellence have developed technologies with independent intellectual property rights, and successively built factories with a scale of over 10,000 tons. Especially Sichuan Gushan produces biodiesel from vegetable oil wastes. The performance of the products is comparable to that of diesel No. 0. The waste emission index after combustion meets the German DIN51606 standard. This marks the birth of biodiesel, a high-tech industry in China. Biodiesel production by enzymatic method has also made great progress. In 2007, Qinhuangdao, Hebei Province, invested in leading science and technology to build the first domestic biodiesel industry with an annual output of 100,000 tons. This technology ranks the leading level in China. Overall, the development of biodiesel in China is good, and biodiesel has attracted more and more attention.
As a high-quality alternative to diesel fuel, biodiesel is an environmentally friendly green fuel, which has great strategic significance for the adjustment of agricultural structure, energy security and comprehensive management of ecological environment in China. With the completion of the 12th Five-Year Plan for China’s national economic and social development and the determination of the goal of building a well-off society in an all-round way in the 13th Five-Year Plan, the demand for energy is increasing day by day, which requires increasing the proportion of biodiesel in China’s energy consumption. The development potential of biodiesel industry is enormous. National science and technology management departments should further strengthen policy support, clarify the orientation of industrial development, implement tax incentives and carbon dioxide emission reduction subsidies, effectively reduce production costs, and make green biodiesel more widely used.