Opportunities and challenges of bio-gas industry under the background of "dual carbon"

1. What is biogas?

Using biomass as raw material, combustible gas produced by thermochemical conversion or biochemical conversion, obtained after reforming, separation, purification and other treatment, with methane as the main component, and in accordance with GB 17820 (natural gas standard) gas.

Biogas comes from biogas purification and is generally obtained by anaerobic fermentation from various urban and rural organic wastes such as crop stalks, livestock manure, kitchen waste, agricultural and sidelide product processing wastewater and other raw materials. It is a green, low-carbon, clean and renewable fuel.

Since the development of rural biogas in the 1950s, China's biogas industry has realized the upgrading from household biogas to various biogas projects and large-scale biogas, and has disposed of urban organic solid waste through anaerobic fermentation of kitchen waste and industrial wastewater through organic wastewater biogas projects. It has formed a multi-dimensional organic waste treatment pattern in agricultural industry and urban life, and realized the synergistic effect of environmental disposal, resource utilization and renewable energy production.

2, biological natural gas process route

Biological gas preparation process diagram

Biomass conversion and purification of bionatural gas engineering include four parts: raw material pretreatment, anaerobic fermentation, biogas purification and biogas slurry disposal, while derived carbon dioxide products and organic fertilizers and other ancillary products.

3, biological gas engineering emission reduction accounting

In this paper, some agricultural waste disposal bio-gas projects in northern China are investigated, and the production data are as follows (Note: Because the survey only obtained rough data, it cannot match specific projects, here for readers' reference).

The biogas project with an annual output of 10 million cubic meters of biological natural gas, in order to facilitate accounting, this paper only discusses the process agricultural waste of straw + cow manure, which is expected to use 50,000 tons of corn straw and 10,000 tons of cow manure (water content of 80-90%) annually. At the same time, in order to ensure the temperature of the fermentation tank during use, about 8,000 tons of biomass pellet boiler is used to heat. Biogas purification, blender operation, plant lighting, raw material pretreatment and other aspects consume 10 million degrees of electricity.

When calculating the emission reduction of biological gas project, the whole calculation is divided into three steps:

At the source, the accumulation of livestock and poultry manure and natural fermentation produce methane and nitrous oxide resulting in carbon emissions. If crop straw is naturally deposited or returned to the field for use, microbial action will also produce carbon emissions. Through the biological natural gas project, livestock manure and crop straw are used as raw materials, and the emissions caused by the original treatment can be counted as emission reduction.

In the production process, in order to maintain the temperature of the fermenter in the plant and the normal operation of various equipment, biomass molding fuel and electricity are needed, and this part is classified as carbon emission;

Terminal substitution, when the produced biological natural gas enters the residential or vehicle gas, it can replace the corresponding amount of fossil natural gas use, and the replacement amount can be counted as emission reduction.

According to the above method, the emission reduction of the investigated project is calculated.

Source emission reduction: The natural stacking of cow manure will produce methane and nitrous oxide, resulting in carbon emissions of 0.09 million tons of CO2 equivalent, while the methane generated by crop straw fermentation in natural environment will not be calculated in this paper due to the limitations of data acquisition and calculation methods.

Terminal replacement: According to the annual output of 10 million cubic meters of biological natural gas to replace residential natural gas consumption, is expected to reduce 21,700 tons of carbon dioxide emissions.

Production link: The use of biomass fuel in the production process is expected to produce carbon emissions of 0.1,200 tons of carbon dioxide equivalent, and the production of electricity emissions is expected to produce indirect emissions of 0.58 tons of carbon dioxide equivalent.

After accounting, from the perspective of raw material disposal of organic matter and terminal energy substitution, the project is expected to reduce emissions by 15,600 tons of carbon dioxide equivalent in one year of operation.

Note: Baseline emissions refer to emissions caused by natural accumulation of corn stalk, cow manure and natural gas utilization; Project emission refers to the emission generated during the production and preparation of biological gas engineering. Emission reduction refers to the emission reduction effect generated by the implementation of the project for one year.

According to the national "Guiding Opinions on Promoting the Development of biological gas Industrialization" for the future of biological gas development goals planning, by 2025, the annual output of biological gas more than 10 billion cubic meters. By 2030, the annual production of biogas will exceed 20 billion cubic meters. According to the analogy calculation of the above method, it is expected to produce 15.6 million tons of emissions reduction, 31.2 million tons (here the agricultural waste disposal potential is calculated).