What is biomass
Biomass refers to various organisms formed directly or indirectly through photosynthesis, including plants, animal waste, garbage and organic wastewater. The so-called biomass energy is the form of energy that solar energy stores in the form of chemical energy in biomass. It is a renewable energy source that can be stored and transported by biomass. Biomass, which the main components is similar to conventional fossil energy sources such as petroleum and coal, are C-H compounds, so its characteristics and utilization methods are very similar to those of fossil fuels, and can make full use of the conventional energy technologies that have been developed.
The development and utilization of biomass energy is one of the advantages of developing and utilizing biomass energy.
Biomass specifically includes:
Wood, crops (rice straw, wheat straw, bean, cotton, husk, etc.), weeds, algae, etc., which are often seen in plants;
Others like animal droppings, animal carcasses, organic components in waste water, and organic components in garbage are also kinds of biomass.
Biomass has four distinct characteristics:
Biomass energy can be regenerated through photosynthesis of plants, so biomass energy is an inexhaustible source of renewable energy;
The biomass has a low sulfur content, a nitrogen content, and a low ash content, and the combustion process produces less SOx, NOx, and ash;
Easy to gasify
The age of biomass formation is much shorter than conventional fossil energy such as petroleum and coal. Therefore, biomass has high volatile components and is easier to gasify as a cleaner energy source;
Biomass is the fourth largest primary energy source in the world, second only to coal, oil and natural gas.
How to use biomass as an energy in different ways
According to REN21’s Global Renewable Energy Status Report 2017, the total global biomass energy utilization in 2017 is about 60EJ (equivalent to 2 billion tons of standard coal), accounting for about 11% of the total global energy consumption.
There are many ways to use biomass, which are generally divided into three types: solid biomass fuel, liquid biomass fuel, and gaseous biomass fuel.
Solid biomass fuel
Solid biomass fuels include direct combustion and biomass briquetting.
Direct combustion such as crop straw, fuelwood, and garbage through direct combustion to obtain thermal energy, which is the most important way of utilizing biomass energy at present.
biomass briquetting is briquetting agricultural and forestry waste, make them become the solid biomass fuel such as straw, wood chips, etc. It will increase the energy density and facilitate transportation. In 2017, the utilization of solid biomass fuel was about 45EJ, accounting for 77% of total biomass energy consumption, and biomass production fuel production was about 28 million tons.
Liquid biomass fuel
Liquid biomass fuel uses biomass as a raw material to produce liquid fuel, thereby improving biomass utilization efficiency and expanding application range. For example, biomass is used to make liquid fuels such as fuel oil, alcohol fuel, and biodiesel. In 2017, global biomass liquid fuels were approximately 133 billion liters, of which fuel ethanol accounted for approximately 67%, and advanced biofuels such as biodiesel and small amounts of hydrogenated vegetable oil accounted for approximately 33%.
Gaseous biomass fuel
Gaseous biomass fuels use biomass to make biomass into gaseous fuels, thereby increasing combustion efficiency and reducing emissions of combustion pollutants. For example, biomass biogas, biomass gasification, and biomass hydrogen production. In 2017, global biogas production was about 56.8 billion cubic meters.
How to use biomass to generate electricity
Biomass power generation is one of the ways of biomass energy utilization, in addition to biomass heating, biomass gas and biomass liquid fuel. There are five types of biomass power generation: direct combustion power generation, hybrid power generation, gasification power generation, biogas power generation, and waste incineration power generation.
Direct combustion power generation
The biomass is directly burned in a boiler, and steam is produced to drive steam turbines and generators to generate electricity. Key technologies for biomass direct combustion power generation include biomass feedstock pretreatment, boiler corrosion protection, boiler feedability and fuel efficiency, and steam turbine efficiency.
Hybrid power generation
Biomass and coal are mixed as fuel to generate electricity, which is called biomass mixed combustion power generation technology.
There are two main types of mixed combustion.
One is that the biomass is directly mixed with coal and put into combustion. This method is highly demanded for fuel processing and combustion equipment, and not all coal-fired power plants can be used.
Another is the combustion of gas and coal produced by biomass gasification, The combustion produced in this mixed combustion system is sent to the steam turbine generator set together.
Gasification power generation
The biomass is converted into a gaseous fuel in a gasifier, and after purification, it directly enters the gas engine to generate electricity or directly enters the fuel cell to generate electricity. One of the key technologies of gasification power generation is gas purification. The gas produced by gasification contains certain impurities, including ash, coke and tar. It needs to be removed by the purification system to ensure the normal operation of the power generation equipment.
Biogas power generation
The biogas generated by the anaerobic fermentation process of a large amount of organic waste in industrial and agricultural or urban life drives the generator set to generate electricity. The equipment used for biogas power generation is mainly an internal combustion engine, which is generally modified from a diesel unit or a natural gas unit.
Waste incineration power generation
Waste-to-energy generation includes waste incineration power generation and waste gasification power generation.
Waste incineration power generation uses the heat released by the combustion of waste in an incineration boiler to heat the water to obtain superheated steam, and promotes the turbine to drive the generator to generate electricity.
The waste incineration technology mainly includes layered combustion technology, fluidized bed combustion technology, rotary combustion technology, etc.
Future of biomass power generation
Globally, biomass resources are abundant, producing about 85 billion tons of standard coal per year, equivalent to 4.5 times the total global energy consumption in 2017. According to the International Energy Agency, the global biomass resource availability is 100-300 EJ (equivalent to 3.4-102 billion tons of standard coal), and it is estimated that by 2050, approximately 160 EJ (5.46 billion tons of standard coal) of biomass will be available worldwide. According to the Renewable Energy Roadmap 2030 issued by the International Energy Agency IRENA, renewable energy will account for 36% of global energy consumption in 2030, of which biomass will account for 60% of renewable energy. Biomass energy will play an important role in future energy substitution.
Biomass power generation mainly includes solid biomass power generation, garbage power generation, and biogas power generation. By the end of 2017, the global installed capacity of biomass power generation reached 106.4 million kilowatts, and the power generation capacity was about 464 billion kilowatt hours, accounting for 1.4% of the global power generation. In the future, global energy consumption will continue to steadily and accelerate the transition to energy cleanliness. Because biomass is the only renewable energy source that can be stored and transported, and with other advantages of cleanness, environmental protection and scale development, biomass energy is the most promising renewable energy source. The proportion of biomass used for power generation will gradually increase in the future. The biomass power generation industry has broad prospects for development in the long run.
While optimistic about the biomass industry, it is also necessary to recognize some of the issues facing the development of biomass. Compared with traditional energy sources, biomass energy has the disadvantages of scattered distribution, low density, complex composition and periodicity of production, which increases the difficulty of biomass energy development and makes it difficult to compete with conventional fossil energy in the market. Therefore, countries are In the development process of the biomass power generation industry, policy support and financial support have been carried out, and efforts have been made to improve the technical level and market competitiveness of the biomass power generation industry.