Biomass pellets, as a clean and renewable biomass energy source, can play a significant role in reducing urban smog when replacing fossil fuels (especially coal) by significantly reducing pollutant emissions. Their effectiveness in reducing smog emissions stems from the combined advantages of fuel characteristics, combustion mechanisms, and environmental attributes. This can be analyzed from the following aspects:
1. Core pollutants of smog and the logic of reducing emissions with Biomass pellets
The main causes of urban smog are the excessive accumulation of pollutants such as fine particulate matter (PM2.5), sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and volatile organic compounds (VOCs) in the atmosphere. Coal combustion and industrial fuel burning are important emission sources.
Biomass pellets are formed by compressing plant-based raw materials such as straw, wood chips, and bamboo chips. The characteristics of pollutant emissions during their combustion process differ fundamentally from those of fossil fuels (especially coal). The core logic is: by replacing high-pollution fuels, the generation and emission of smog-related pollutants are reduced at the source.
2. Specific manifestations of Biomass pellets in reducing smog pollutants
（1） Significantly reducing sulfur dioxide (SO₂) emissions and reducing sulfate pellets
High sulfur emissions from coal combustion: The sulfur content of coal (especially thermal coal) is typically between 0.5% and 3%, and during combustion, it generates a large amount of SO₂. SO₂ further oxidizes in the atmosphere to form sulfate (SO₄²⁻), which is the main component of PM2.5 (accounting for up to 20%-40%), directly exacerbating smog.
The low sulfur advantage of Biomass pellets: The natural sulfur content of biomass raw materials (such as straw, wood) is extremely low (typically <0.1%), and SO₂ emissions during combustion are only 1/20-1/50 of those from coal (measured data show that the SO₂ emission concentration of Biomass pellets is generally <50mg/m³, while unscrubbed coal can reach over 1000mg/m³). This reduces the generation of sulfate pellets at the source.
（2）Reducing nitrogen oxides (NOₓ) emissions and lowering nitrate pellets
High NOₓ emissions from coal combustion: Coal combustion temperatures are high (flame temperatures often reach over 1500°C), and nitrogen in the air reacts with oxygen at high temperatures to form a large amount of NOₓ (mainly NO and NO₂). NOₓ is converted to nitrate (NO₃⁻) in the atmosphere, which is also an important component of PM2.5, and participates in photochemical smog formation.
The low nitrogen characteristic of Biomass pellets: The nitrogen content of biomass is typically 0.3%-1.5% (much lower than that of coal, which is 1%-2%), and the combustion temperature is relatively low (through optimized combustion technology, it can be controlled at 800-1000°C). NOₓ generation is only 1/3-1/2 of that from coal. If combined with low-nitrogen burners, NOₓ emissions can be further reduced to below 50mg/m³, significantly reducing nitrate pellet emissions.
（3）Reducing direct emissions of particulate matter (PM2.5, PM10)
Particulate matter pollution from coal combustion: When coal combustion is insufficient, a large amount of fly ash (containing carbon pellets and ash) is produced, with PM2.5 accounting for a high proportion (pellet size <2.5 micrometers, which can directly enter the lungs), and it adsorbs heavy metals (such as mercury, lead) and toxic organic compounds, exacerbating the health hazards of smog.
Clean combustion of Biomass pellets:
Biomass pellets have high density (1.1-1.3g/cm³) and a dense structure, resulting in less fly ash production (only 1/10-1/20 of that from coal);
The ash content of the raw materials is low (typically <5%, while coal has a high ash content of 10%-30%), and the residue after combustion is less, and the residue can be used as organic fertilizer raw material to avoid the spread of ash pellets into the atmosphere. The actual measurement data shows that the PM2.5 emission concentration from the combustion of biomass pellets is usually less than 30mg/m³, while the emission from untreated coal combustion can reach over 500mg/m³.
Biomass pellets can reduce the emissions of core pollutants such as SO₂, NOₓ, and PM2.5, which are the main causes of smog, by replacing high-polluting fossil fuels at the source. At the same time, their carbon-neutral characteristics can improve the atmospheric environment. This is a cost-effective and environmentally friendly solution for urban smog control. With technological progress and policy support, their proportion in the urban energy structure will continue to increase, providing continuous impetus for alleviating smog and improving air quality.