Biochar is a valuable resource produced by pyrolysis of waste biomass. Due to its excellent performance in carbon sequestration, soil improvement, feed additive, etc., biochar has gradually attracted global attention. As the application field of biochar continues to expand, its quality assessment is becoming more and more important. The molar H/C ratio, as a key parameter, has a profound impact on the quality assessment of biochar.
Basic Definition & Significance of Molar H/C Ratio
The molar H/C ratio refers to the ratio of the number of moles of carbon atoms (C) to hydrogen atoms (H) in biochar. According to the European Biochar Certification (EBC), biochar with a ratio below 0.7 is qualified. It is worth emphasizing that the “C” here refers to the organic carbon (Corg) in the biochar rather than the total carbon. This ratio directly reflects the degree of carbon fixation and the residual amount of hydrogen in the biochar, and is an important indicator for evaluating the degree of pyrolysis of biochar, chemical stability and its long-term performance in the environment.
Sufficiency of Biochar Pyrolysis
From a chemical point of view, the lower the carbon-hydrogen molar ratio of biochar, the stronger the aromaticity of the carbon chain in its internal structure. High aromatic structures are usually associated with more suitable pyrolysis temperatures. This indicates biochar has undergone a sufficient carbonization process to form stable carbon skeleton.
Stability & Durability of Biochar
The lower the carbon-hydrogen molar ratio, the higher the stability of the biochar. This means that the biochar can exist for a long time in the soil or other environments. Therefore, it is not easily decomposed by microorganisms or chemical degradation. Therefore, biochar has a low carbon footprint lifecycle and longer carbon sequestration time.
Effect of Raw Material Selection on Biochar Molar H/C Ratio
The raw materials for biochar production include waste biomass such as wood, agricultural waste, and fruit shells. Lignin and cellulose are the main components of these biomass. However, their different proportions lead to different molar H/C ratios of the produced biochar. For example:
High Lignin
Biomass such as wood and coconut shells usually contain a high proportion of lignin. This complex organic compound easily forms a stable carbon skeleton at high temperatures. Therefore, biomass with a higher lignin content usually produces biochar with a lower H/C ratio.
High cellulose
Biomass such as straw and rice husks contain more cellulose and hemicellulose. They are more likely to form volatile products during pyrolysis. However, the hydrogen content in these volatile substances is higher. Therefore, these biomasses produce biochar with a higher H/C ratio.
Effect of Pyrolysis Process on Biochar Molar H/C Ratio
The production of biochar mainly relies on pyrolysis technology, which is to heat biomass in a micro-oxygen environment. The pyrolysis temperature, time and other parameters of biochar production equipment affect the H/C ratio of biochar:
- Temperature: Higher pyrolysis temperature helps to increase the carbonization degree of biochar and reduce the H/C ratio.
- Time: Longer pyrolysis time helps to further decompose volatile substances, increase carbon content, and thus reduce the H/C ratio.
The following is the process flow of biochar production equipment for your reference:
Written at the End
With the advancement of technology and changes in application needs, in-depth research on the molar H/C ratio of biochar will promote its application and development in more emerging fields. Start your biochar production project to help achieve sustainable development and global carbon reduction goals. Beston Group looks forward to being your partner on the road to success.