Bioenergy, also known as green energy, refers to the energy obtained from biomass, which is the earliest energy used by human beings. The ancients used wood to make fire and cut firewood to burn charcoal, in fact, they were using bio energy. "Everything grows on the sun", and bioenergy is converted from solar energy. As long as the sun is not extinguished, bioenergy will be inexhaustible. Its transformation process is to synthesize carbon dioxide and water into biomass through photosynthesis of green plants. The use process of bioenergy also generates carbon dioxide and water, forming a material cycle. Theoretically carbon dioxide The net emission of is zero. Bioenergy is renewable clean energy The development and use of bioenergy are in line with the concept of sustainable scientific development and circular economy. Therefore, the use of high-tech means to develop bioenergy has become an important part of the energy strategy of the developed countries in the world. However, the energy obtained by direct combustion of biomass is inefficient and uneconomical. along with industrial revolution With the large-scale use of fossil energy, bio energy is gradually replaced by fossil energy represented by coal, oil and natural gas. However, with the rapid development of industrialization, fossil energy has also been used on a large scale, which has produced a large number of pollutants and destroyed the ecological balance of nature. In order to achieve sustainable development, and the drawbacks of fossil energy have become increasingly apparent, the development and utilization of bio energy has been emphasized by people. The carrier of bioenergy is organic matter, so this energy exists in the form of physical objects, and it is the only renewable energy that can be stored and transported. Moreover, it is the most widely distributed, not limited by weather and natural conditions. As long as there is life, there is biomass. From the perspective of utilization mode, biomass energy is similar to coal and oil in internal structure and characteristics, and can be treated and utilized by the same or similar technologies. The development and promotion of utilization technologies are relatively easy. In addition, biomass can be converted through certain advanced technologies. In addition to being converted into electricity, it can also generate oil, gas or solid fuel, which can be directly used in transportation machinery such as automobiles or diesel engines gas turbine , boilers and other conventional thermal equipment can be used in almost all aspects of human industrial production or social life. Therefore, among all new energy sources, biomass energy has the greatest compatibility with modern industrial technology and modern life. It can replace conventional energy without any improvement of existing industrial technology, It has great substitution ability for conventional energy, which is the basis for biomass energy to play an important role in the future. [1] As a renewable and extremely pollution-free energy, bioenergy has incomparable advantages and will certainly inject a strong impetus into economic development and environmental protection in the 21st century. Compared with oil, coal and other energy sources, bioenergy has the following characteristics:
(1) Biomass energy has little environmental pollution during combustion. Biomass energy produces carbon dioxide in the burning process, and the carbon dioxide emitted can be grown by the same amount Plant photosynthesis Absorption and zero emission of carbon dioxide, which is extremely beneficial to reducing the carbon dioxide content in the atmosphere and reducing the "greenhouse effect". (2) Biomass energy has a huge content and belongs to renewable energy. As long as there is sunshine, the photosynthesis of green plants will not stop, and biomass energy will not be exhausted. Vigorously promote tree planting, grass planting and other activities, not only plants will continue to supply biomass energy raw materials, but also improve the ecological environment.
(3) Biomass energy has the characteristics of universality and accessibility. Biomass energy exists in all countries and regions in the world, and is cheap, easy to access, and the production process is very simple.
(4) Biomass energy can be stored and transported. Among renewable energy sources, biomass energy is the only energy that can be stored and transported, providing convenience for its processing, conversion and continuous use.
(5) Biomass energy has high volatile components, high carbon activity and is flammable. At a temperature of about 400 ℃, most of the volatile components of biomass energy can be released, and it is easier to convert it into gas fuel. After the combustion of biomass energy, there is less ash and it is not easy to bond, which can simplify the ash removal equipment.
In terms of the overall composition of biomass energy resources, biomass energy accounts for more than 70% of the total biomass energy in China's rural areas, and the rest is mainly urban life, sewage and forestry waste Biomass resources In terms of utilization, the main components are mainly forestry waste and firewood forest. With the development of fuel forest technology and the improvement of industrial level in China, the proportion of this aspect will also become larger and larger, so the development and utilization of this aspect can not be ignored. In addition, the development of bioenergy has the following advantages:
(1) Bioenergy is the only energy product that can replace petroleum fuel on a large scale. Water energy, wind energy, solar energy, nuclear energy and other new energies are only applicable to power generation and heating.
(2) Diversity in bioenergy products. Energy products include liquid bioethanol and diesel, solid prototype and shaping fuel, gaseous biogas and other energy products. It can not only replace oil, coal and natural gas, but also provide heat and power.
(3) Diversity of bio energy raw materials. Biofuels can use crop straws, forestry processing residues, livestock manure, organic wastewater and waste residue of food processing industry, urban garbage, and can also use low-quality land to grow various energy plants.
(4) The "materiality" of bioenergy can produce various materials such as plastics, fibers, and chemical raw materials like petroleum and coal, forming a huge biochemical production system. This is impossible for other renewable and new energy sources.
(5) The "recyclability" and "environmental protection" of bioenergy. Biofuels are products produced in the harmless and resourceful process of agricultural, forestry and urban and rural organic wastes; All living materials of biofuels can enter the biological cycle of the earth, and even the released carbon dioxide It will also be re absorbed by plants and participate in the earth's cycle, so as to achieve zero emissions. Material sustainability and resource recyclability are modern advanced production modes. (6) The "driving force" of bioenergy. Biofuels can expand the field of agricultural production, drive rural economic development and increase farmers' income; It can also promote the development of manufacturing, construction, automobile and other industries. The development of biofuels in China and other countries can also promote agricultural industrialization and the development of small and medium-sized cities, narrow the gap between industry and agriculture, which has important political, economic and social significance.
(7) Bioenergy has a "restraining effect" on the price of crude oil. Biofuels will increase the number of "crude oil" producing countries from 20 to 200. By independently producing fuels, we will curb the price of imported oil and reduce the cost of imported oil, so that more funds can be used to improve people's lives and fundamentally solve the food crisis.
(8) Bioenergy can create jobs and build domestic demand markets. Brazil's experience shows that one job in the petrochemical industry can create 152 jobs in the ethanol industry; The investment to create one job in the petrochemical industry is $220000, while the investment in the fuel industry is only $11000. According to the "Green Jobs" report released by the United Nations Environment Programme, "the renewable energy industry will create 20.4 million jobs by 2030, including 12 million biofuels." [1]
Bioenergy can be divided into sugar, starch and lignocellulose according to the chemical properties of raw materials. According to the source of raw materials, it can be divided into: agricultural production waste, mainly crop straw, firewood and firewood, agricultural and forestry processing waste, wood chips, grain shells and fruit shells; Human and livestock manure and living organic matter, etc; Industrial organic waste, organic wastewater and waste residue; Energy plants include all crops, trees and aquatic plant resources that can be used as energy. Bioenergy itself can be divided into the following categories:
Agricultural waste refers to the residues produced in the farmland when crops are harvested, including grain, root crops and sugarcane residues. Forest waste refers to the waste generated when the wood processing department manufactures various primary wood products from raw materials, and the waste generated when the wood utilization department forms secondary products such as buildings from primary wood products.
2. Organic sewage
Organic sewage refers to the discharged wastewater rich in organic matter, including industrial sewage, agricultural sewage and domestic sewage. Due to the outstanding characteristics of cleanness, high efficiency, and renewable, hydrogen as an energy source has attracted increasing attention. Hydrogen production methods include water electrolysis, thermochemical method, photoelectrochemical method, plasma chemical method and biological hydrogen production method. From the perspective of the cost of biological hydrogen production, the cost of hydrogen production from these single matrices is relatively high, while hydrogen production from cheap and complex matrices such as industrial and agricultural organic wastewater can make waste materials resourceful and reduce its production cost. The technology of hydrogen production by mixed strains has gradually matured and achieved great results.
3. Livestock manure
Livestock manure is also an important biomass energy. In addition to a small amount of direct combustion in pastoral areas, livestock manure is mainly used as raw material for biogas fermentation. The main livestock in China are chickens, pigs and cattle. According to the variety, weight, fecal excretion and other factors of these livestock, fecal resources can be estimated.
4. Domestic garbage
With the expansion of urban scale and the acceleration of urbanization process, the production and accumulation of urban garbage in China are increasing year by year. Urban domestic waste is mainly a mixture of household, commercial, service industry and a small amount of construction waste. Its composition is relatively complex, and its composition is mainly affected by Living standard of residents , energy structure, urban construction, green area and seasonal changes. [1] While the upsurge of bioenergy development is taking shape, there are also some factors restricting the development of bioenergy, mainly as follows:
(1) Competition with grain for land and livestock for feed, especially the development of biofuels based on grain, has been questioned or resisted by some developing countries.
(2) There is a lack of technology and production standards, and there is a certain conflict with the existing production and sales system of traditional energy.
(3) Cost price disadvantage.
(4) Early support and supporting issues of laws and policies.
Therefore, for the future development trend of bioenergy, it is not only necessary to return to rationality, calmly treat and analyze the current development boom of bioenergy, but also to adopt appropriate policies and regional division of labor and cooperation from demonstration to standardization. [2]
