Biomass energy has great potential to achieve carbon peak and carbon neutrality in China



1. Coal power emissions account for the largest share of China's carbon emissions

The International Energy Agency pointed out in its "2050 Energy Zero Emissions Roadmap report" that the key energy sectors for CO2 emissions are power, industry, transportation and buildings, and stressed that the power sector should be the world's first zero carbon emission areas. The report proposes a road map for coal power plants to be phased out completely by 2040, starting with the least energy-efficient subcritical units. China's total installed capacity of coal-fired power generation has reached 1.1 billion kilowatts by 2021, although its share has been reduced to less than 50%, but the proportion of coal power generation is still more than 60%. In 2020, China's carbon emissions will total 11.3 billion tons, of which 9.9 billion tons will be emitted from the energy sector, accounting for 88%. China's thermal power generation was 5,333 billion KWH, and the actual statistical data of carbon emissions was 5.12 billion tons, accounting for 51.76% of China's total CO2 emissions that year. Moreover, with the deepening of industrialization and urbanization, China's total energy consumption will peak around 2030, and electricity demand will continue to grow. The harsh reality is that to achieve carbon peak and carbon neutrality, energy is the main battlefield, and coal power carbon reduction is the main force. Without first achieving substantial carbon reduction in coal power, the "dual carbon" goal is impossible to achieve.

irreplaceable

According to China's power development plan, by 2030, the total installed capacity of renewable wind power and solar power generation will reach more than 1.2 billion kilowatts, but under the "double carbon target" and the establishment of new energy as the main body of the new power system, it is expected that by 2030, the installed capacity of new energy will greatly exceed the original plan and will reach more than 1.7 billion kilowatts. However, it must be seen that wind power and solar power generation have shortcomings that cannot be ignored, that is, "uncontrollable", which is an unstable intermittent power supply. Its installed power generation capacity is severely limited by natural meteorological conditions such as day and night sunshine, seasonal changes, cloudy or sunny weather, and wind strength. According to reports, in 2019, when the proportion of non-fossil energy generation in the country was only 32.6%, wind power and optoelectronics have generally faced problems such as grid-connection difficulties, absorption difficulties, and scheduling difficulties. In February 2021, due to the cold weather in Texas, the entire state power grid completely collapsed in four minutes. 4.5 million homes and many businesses lost power; Days of power outages killed nearly 100 people. One of the main reasons is that wind power and photovoltaic power supplies, which already account for a considerable proportion of capacity, cannot be produced due to freezing wind blades and continuous haze weather. Frequent power rationing in several southern provinces last winter and spring is due to low rainfall affecting hydroelectric power generation, and poor wind and light conditions affecting the normal operation of wind power and photovoltaic power.

In fact, it will be difficult to replace the basic supporting role of the existing large coal power units in China's electric power production. First of all, China's coal-based power supply structure is determined by China's lack of oil and gas and abundant coal resource endowment characteristics, is more than 70 years since the founding of the People's Republic of China, especially in the past 30 years, the vast number of cadres, workers and technical personnel of the national power front, through self-reliance and hard work, the introduction of digestion and absorption of foreign advanced technology, bold and active innovation established. It has formed the world's largest and leading, rational, stable and reliable coal power production and power transmission and distribution of a huge system, which has strongly guaranteed and supported the country's energy security, production and social development, and the continuous improvement of people's living standards. China has become the world's most powerful coal power production, this historical process and results have a huge inertia, change is not short-term, let alone overnight.

With the adjustment of China's industrial structure and the process of urbanization, the structural changes on the power demand side are obvious, the load instability and the change range increase sharply, which requires the power generation side to have the initiative of deep follow-up, and the power grid scheduling and regulation are highly flexible. As mentioned above, wind power and photovoltaic power generation in the current large-scale energy storage technology has not been breakthrough, can not meet these requirements, while China's large-scale coal power system can adapt to changes in the demand side.

As mentioned earlier, the total capacity of China's large-capacity super (super) critical parameter and sub-critical parameter units has 873 million kilowatts, and the total assets of these units and their supporting facilities and transmission and distribution systems are as high as 10 trillion yuan. This huge asset is the wealth accumulated by the long struggle of the country and the people. Most of these units have not been in service for a long time, and when they are "young" and "young and strong", they must not be easily retired in the name of "low-carbon transformation", causing irreparable huge losses. If the power production capacity of the above coal power system is replaced with a new production, energy storage (there is no mature technology at present) and unstable wind and solar power generation system, the high investment and operating costs will be imagined.

Third, biomass and coal coupling power generation is coal power

Biomass power generation and wind power, solar power and other renewable energy power, are (nearly) zero-carbon emissions of electricity production, but also has wind power and solar power do not have the advantages: that is, in nature, the annual regeneration of agricultural and forest residual resources is relatively stable; Fuel can be transported and stored for balanced use throughout the year. It is an advanced technology to realize biomass power generation in the world by using large and efficient coal-fired units to burn biomass fuel for power generation. It is not only more efficient than the existing biomass direct combustion power generation (generally for small and medium power plants), but also can significantly reduce the carbon emissions of coal power units, improve the flexibility of coal-biomass coupled power generation, and strengthen the sustainability of coal power production, which is a practical and feasible path for coal power to low carbon.

The international use of biomass co-firing technology in large coal-fired power plants stems from the Kyoto Protocol to the United Nations Framework Convention on Climate Change adopted in Kyoto, Japan, in December 1997. The protocol aims to curb global climate change by limiting carbon dioxide emissions in developed countries. Since then, developed countries, especially EU countries, have begun to take various measures in regulations, policies and technologies to reduce carbon emissions from coal power. One of the most important technologies is the use of coal and biomass coupled mixed combustion power generation. After the biomass mixed combustion technology gradually matures, it has been well promoted and applied.

Fourth, Britain and Denmark shut down coal power

Take Denmark, for example. In 2017, modern bioenergy already accounted for nearly seven in 10 (69%) of renewable energy. Its most important contribution is to replace coal with biomass fuel, especially biomass pellet fuel, in the field of cogeneration. Due to the technical solution to the problem that mixed stalks rich in potassium and chlorine are easy to produce boiler coking, in 1992, the midkraft power plant with a power of 78,000 kilowatts used straw and coal to generate electricity, which reached 50%:50% ratio, and digested 70,000 tons of straw annually. In 1999, Denmark has achieved the goal of using 1.2 million tons of straw (accounting for nearly 30% of the national annual output of 3.5 million tons of straw) and 200,000 tons of wood slicing and coal mixed combustion power generation (insufficient raw material imports). Denmark's Energy Information Agency (EnergiNet) estimates that biomass already accounts for more than a quarter of the country's electricity consumption; It is expected that as more biomass (including biogas) cogeneration projects come on stream, this figure will increase to 57% by 2026. In the United Kingdom, driven by strong incentive policies, coal-to-biomass coupled power generation has been strongly developed since the end of the last century. After more than 20 years of practice in coal power plants with biomass coupling and coal-fired power generation, all large coal-fired power plants in the UK have finally been transformed into biomass combined combustion. The most typical is the largest Drax power plant in the UK. The power plant has a total of six 660,000 kilowatt coal-fired units. Starting from the transformation of 5% biomass in a unit in 2003, the biomass ratio has been continuously increased until all coal power units have been transformed into biomass mixed combustion, and finally in 2018, four 660,000 kW coal power units have achieved 100% combustion of biomass pellet fuel. Become the world's largest biomass fuel thermal power plant. At the same time, the plant has solved the supply problem of 10 million tons of biomass pellet fuel per year through two domestic and foreign markets. Therefore, according to their experience, the coal-biomass co-combustion power generation of large coal-fired units is technically very mature, which shows a good way for China's coal power industry to learn from international experience to achieve low-carbon transformation. And the special advantage of China's large coal-fired units is that it can make coal-biomass mixed combustion power generation. One of its advantages is that China's coal-fired units in the world's highest power supply efficiency and the lowest power supply coal consumption, the second has a deep peak load regulation technology, so that the unit load regulation range of 100%-20%, the third is soot, SO2, NOX and other conventional air pollutants can achieve ultra-low emissions.

1. "Green" power generation target, that is, all power generation companies must complete a certain target of carbon zero emission power generation;

3. Penalties for failure to meet "green" power generation targets;

Such successful changes have emboldened the UK and Denmark to announce that they will close all their coal plants by 2025 and 2030, respectively. The experience of countries such as Denmark and the United Kingdom shows that in order for coal-fired thermal power plants to achieve low-carbon development through coal-biomass mixed combustion, three conditions must be met:

2. Establish a reliable supply market for biomass fuel;

The prerequisite is that there must be an adequate and relatively stable supply of biomass fuel. In the aspect of biological raw material resources, our country has the advantage that can not be ignored.

China's national conditions determine that it is impossible for us to import a large number of raw materials for biomass energy like European and American countries. Therefore, the key to the current and future large-scale application of biomass energy in China is firstly the resource potential, and secondly the ability to transform the theoretical resource potential into practical application.

Our accurate estimation of the huge potential of marginal land for planting energy plants is that the three types of marginal land suitable for planting energy plants (shrubs, grasses), namely shrub, woodland and low cover grassland, total 179 million hectares; The net primary productivity (NPP) of 1.8 million land units was first calculated on a 1 km grid, then converted to biomass of energy plants and above-ground (available) biomass, and then converted to energy. The annual energy plant energy plus the estimated annual available organic waste (including crop straw, agricultural product processing residues, livestock and poultry manure, forestry tending, logging and processing residues, municipal household waste, industrial wastewater/domestic sewage and catering waste oil) is converted into energy, The total annual biomass energy resource is 956 million tons of standard coal (considering that livestock and poultry manure, waste, sewage and waste oil are not suitable for coupled power generation, the available biomass resource for power generation is 5.69 tons of standard coal). It is important to emphasize that this resource potential is the situation of energy plants under completely natural (growth) conditions. If artificial cultivation is necessary to increase the input (water, fertilizer, seed selection, etc.) and management, the biomass and energy potential of energy plants can be doubled, quadrupled or even more. At the same time, with the continuous improvement of production and living standards, the amount of urban and rural organic waste resources will continue to increase. Expanding the area of afforestation will also increase the output of the "three residues". Therefore, by then, the annual resources available for biomass will exceed 2 billion tons of standard coal. At present, the amount of coal used for power generation in China is about 1.6 billion tons of standard coal per year.

If you look at it from another perspective, such a huge pillar industry and market with an annual output value of more than one trillion yuan, including an extremely large number of labor positions, is precisely the urgent need to revitalize the countryside. The practice of some biomass direct combustion power plants participating in poverty alleviation in the past few years has proved that there is a large number of abandoned and unharvested agricultural and forest organic matter in rural areas. As long as a perennial purchase station is set up, a weak labor force or even the disabled can earn tens of thousands of yuan a year by collecting and selling these raw materials.

Sixth, some suggestions for high-quality low-carbon power generation in China

1. The first is to adopt the innovative coal power upgrading technology that has been demonstrated and operated, and upgrade the existing coal power units in service. In addition to phasing out the backward, low efficiency and high coal consumption units, all coal power units in service, including the sub-critical, supercritical and ultra-supercritical units of 300,000 kW, 600,000 kW and 1 million kW grades, will be upgraded. Formulate specific power supply coal consumption requirements and carbon emission intensity standards, as well as flexible low load performance requirements, limited time to complete, otherwise not allowed to run online. Strive to complete the upgrading of all coal power units in service as far as possible during the "14th Five-Year Plan" period. To realize the development of high efficiency and low coal consumption of in-service coal power units is actually the basis and premise of realizing the coupling of coal power and biomass power generation.

(3) Formulate a series of policies to promote the cultivation of shrubs, grasses and other energy plants on marginal land and the transformation of forest land, and establish an industrial chain for the collection, storage, transportation and primary processing of agricultural and forest waste and energy plants. Promote the establishment of a national biomass fuel supply and demand market. The utilization of biomass power generation has gradually changed from small direct combustion power plants to large-scale coal-fired power plants.

Three steps are proposed for the high quality and low carbon development of coal power: further eliminate the backward production capacity of coal power; Upgrading of non-state-of-the-art units themselves that still need to remain in service; The development and utilization of biomass coupled cogeneration and CCUS technology for large and efficient coal power units. Among them, the first is the upgrading of in-service units to further reduce coal consumption and carbon dioxide emission; The second is to make the coal-power biomass coupled mixed combustion power generation play a role of connecting the past and the next, and further reduce its carbon emissions on the basis of the innovation and transformation of coal-power itself into a high-efficiency and low-coal consumption flexible unit. This would create a window of time for the adoption of technologies such as CCUS to eventually achieve zero carbon emissions from coal power. The key to promoting the development of coal and biomass coupled mixed combustion power generation in China is to "improve the green low-carbon policy and market system", "formulate and implement the corresponding support and incentive biomass mixed combustion policy" and "establish and develop the supply and demand market system of biomass fuel to achieve the double cycle of domestic and international biomass pellet fuel markets".