What is Biomass Renewable Energy?

According to the definition of the International Energy Agency (IEA), biomass refers to various organisms formed through photosynthesis, including all animals and plants and microorganisms. Biomass energy is the energy form of solar energy stored in biomass in the form of chemical energy. It has always been one of the most important energy sources for human survival. It is the fourth largest energy source after coal, oil and natural gas. Occupy an important position in the system.

Among various renewable energy sources, due to the potential ecological and environmental risks of nuclear energy and large-scale hydropower, regional resource constraints such as wind energy and geothermal energy, vigorous development has been restricted and questioned, while biomass energy has been ubiquitous, abundant, Features such as reproducibility have been recognized. Biomass is unique not only because it can store solar energy, but also as a renewable carbon source that can be converted into conventional solid, liquid, and gaseous fuels. Energy sources such as coal, oil, and natural gas are also transformed from biomass energy. of.

Biomass refers to various organisms produced through photosynthesis using the atmosphere, water, land, etc., that is, all living organic matter that can grow is collectively called biomass.

Features: Renewability. Low pollution. Widely distributed. Abundant resources. Carbon neutral.

Biomass includes plants, animals, and microorganisms.

Broad concept: Biomass includes all plants and microorganisms, as well as animals and food wastes produced by plants and microorganisms. Representative biomass such as crops, crop waste, wood, wood waste and animal waste. Narrow concept: Biomass mainly refers to lignocellulose (such as lignin) in the agricultural and forestry production process, except for grain and fruits, straws, trees, etc., agricultural industry waste, agricultural and forestry waste, and livestock during the production process Feces and waste.

Biomass energy is an important component of renewable energy. The efficient development and utilization of biomass energy will play a very active role in solving energy and ecological environmental problems. Since the 1970s, countries around the world, especially economically developed countries, have We attach great importance to this and actively carry out research on biomass energy application technology, and have achieved many research results, reaching the scale of industrial application. This article summarizes the research and development progress at home and abroad, involving biomass energy solidification, liquefaction, gasification and direct combustion. And other research technologies. ^[1]

carbohydrate:

Common sugars are

There are many types, each with different characteristics and attributes, and the utilization technology is complex and diverse. Looking at domestic and foreign biomass utilization technologies, they are all converted into solid, liquid, and gaseous fuels for efficient use. The main ways are: ^[2]

Chinese pair

Biomass includes organic matter produced by plants through photosynthesis (such as plants, animals and their excreta), waste and

The price of renewable energy generation determines that biomass power generation can subsidize 0.25 yuan per kilowatt hour

Xinhuanet, Beijing, January 12 (Reporter Lu Nuo) China's renewable energy power generation prices are implemented in government pricing and government guidance pricing. Where the on-grid electricity price of biomass power generation projects is implemented by the government, the electricity price standard consists of the benchmark on-grid electricity price of desulfurized coal-fired units in 2005 in various provinces (autonomous regions and municipalities) plus a subsidized electricity price of 0.25 yuan per kilowatt hour. ^[4]

Biomass can now be applied to buildings such as doors and windows and floors. As listed below:

· Chinese government aid to Laos International Conference Center ^[5]

The process for preparing acetic acid from wood fiber plant raw materials mainly includes pretreatment, enzymolysis, fermentation and rectification.

(1) Pretreatment

Natural lignocellulose is difficult to be degraded by cellulase, so natural lignocellulose must be pretreated first.

Traditional pretreatment methods include acid method, alkaline method and biological method. The acid method can effectively degrade hemicellulose, but cannot separate cellulose and lignin, and the acid has a problem of corrosion of the material of the equipment. The alkali needs to be neutralized later to generate a large amount of salt, which increases the burden of wastewater treatment. The alkaline method can destroy lignin, but cannot separate cellulose and hemicellulose, and generate a large amount of black liquor, causing environmental pollution. Alkali is also difficult to recycle. Biological methods are still mainly in the laboratory research and development stage, and there is still a long way to go before industrialization requirements.

Compared with the above traditional pretreatment methods, the steam blasting method is characterized by low processing cost, low pollution, and low energy consumption, so it has become the most commonly used pretreatment method. Steam blasting uses high-temperature and high-pressure water vapor to partially hydrolyze hemicellulose in lignocellulosic raw materials and soften lignin, thereby reducing the polymerization degree of cellulose, hemicellulose, and lignin. The gas inside the lignocellulose expands rapidly, causing a blasting effect and further destroying the internal structure of the lignocellulose. The general process of steam blasting is that lignocellulose is first cut and coarsely crushed, and dust and impurities are removed, and then impregnated with water and transported to the pretreatment reactor. At a certain temperature (170 ~ 200 ° C) and pressure in the pretreatment reactor (0. 8 ~ 1.0 MPa) in the steam for a certain period of time (5 ~ 25 min), and then the pressure is released and crushed instantly to obtain the pretreated material.

(2) Enzymolysis

After the lignocellulose is pretreated, it needs to be further hydrolyzed to fermentable sugars.

The traditional acid hydrolysis technology is relatively mature, but the corrosive nature of the acid is harmful to the human body, the required process conditions are harsh, and the equipment investment and production costs are increased.

Compared with acid hydrolysis, enzymolysis is characterized by mild reaction conditions and no pollution, so it has become a commonly used lignocellulose hydrolysis process.

Cellulase is a catalyst for the enzymatic hydrolysis process. It is a group of enzymes that can hydrolyze cellulose and hemicellulose in lignocellulose to produce monosaccharides. Cellulase can pass Trichoderma, Aspergillus, Rhizopus and Penicillium This kind of fermentation is prepared by yourself, and commercial enzyme preparations can also be used.

The general process of enzymatic hydrolysis is to first prepare the pretreatment material and water to a certain substrate concentration, and then add cellulase to start the enzymatic hydrolysis. The enzymatic hydrolysis process needs to be controlled at a certain temperature and pH. After a certain enzymatic time is reached, the enzymatic hydrolysis is obtained. liquid. The main operating conditions of the enzymatic hydrolysis process are substrate concentration, amount of enzyme, enzymatic time, enzymatic temperature, and enzymatic pH. The increase of substrate concentration will affect the heat and mass transfer and homogeneity of the enzymatic hydrolysis reaction, and the production of high concentrations of enzymatic hydrolysis products will have feedback inhibition on the enzyme, so the substrate concentration is generally controlled between 15% and 30%; The pH is determined by the optimal activity of the enzyme preparation. The general enzymatic hydrolysis temperature is 50 ° C and the enzymatic hydrolysis pH is 5.0. It is advisable to control the enzymatic hydrolysis time in 2 to 3 days. The enzymatic hydrolysis time is too long, which may cause partial fermentation. Degradation of sugar.

The enzymolysis solution can be washed with water to separate lignin, or it can be directly fermented to produce ethanol without washing with water.

(3) Fermentation

The ethanol fermentation process is relatively mature, and hexose fermentation can be completed more easily with Saccharomyces cerevisiae. However, traditional Saccharomyces cerevisiae can only convert hexose to ethyl yeast, but cannot use pentose.

Using genetic and metabolic engineering techniques to screen out pentose fermentation strains, full utilization of hexose and pentose can be achieved.

The full utilization process of hexose and pentose can be divided into two processes: separate fermentation of hexose and pentose, and simultaneous fermentation of hexose and pentose. Separate fermentation of hexose and pentose requires first washing the pretreated material to separate pentose. The process needs to consume a lot of water, so hexose and pentose are generally used in the simultaneous fermentation process.

The general process of simultaneous fermentation of hexose and pentose is to inoculate co-fermentation bacteria in the enzymatic hydrolysis solution. The fermentation process needs to be controlled at a certain temperature (35 ° C) and pH (6.0) to reach a certain fermentation time (about 1-2 days). To get fermented mash.

The fermented mash can be recovered by centrifugation, and the ethanol in the fermentation tail gas can be recovered and then rectified.

(4) Distillation

The low-concentration ethanol in the fermentation broth needs to be concentrated by rectification.

The rectification of ethanol can adopt the production method of three-column two-effect differential pressure distillation. This method is characterized by the use of multi-stage thermal coupling technology and the use of system heat in stages to make the use of heat as optimal as possible, while also saving Up steam consumption. After rectifying the low-concentration ethanol in the fermentation broth, 95% (volume fraction) of azeotropic ethanol can be obtained. ^[6]