Biochar

Definition of Biochar

Biochar is not the charcoal traditionally used for fuel, but a carbon-rich, refractory and stable solid material obtained through special processing. Biochar can be used in water treatment to remove heavy metals, organic matter and color. At the same time, biochar can be used for soil improvement, etc., and its application is wide and has attracted much attention.

Source of Biochar

The raw materials of biochar come from a wide range of sources, mainly including biomass such as forest residues, agricultural residues (such as corn stalks, straw, etc.), urban solid waste, energy crops and animal manure. These biomasses can be prepared into biochar through thermochemical conversion processes such as high-temperature pyrolysis in an oxygen-deficient environment.

Byproducts of Biochar Preparation

During the preparation of biochar, a variety of byproducts are produced. The types and quantities of these byproducts depend on the specific preparation method and operating conditions.

Gaseous byproducts

Carbon monoxide (CO) and carbon dioxide (CO₂): In the early stage of biomass pyrolysis (usually below 270°C), hemicellulose in the biomass begins to decompose, producing carbon monoxide and carbon dioxide. These gases are inevitable products of the pyrolysis process, and their production is related to factors such as the type of raw materials, pyrolysis temperature and time. Hydrogen (H₂) and methane (CH₄): When the pyrolysis temperature reaches between 360°C and 400°C, the organic matter in the biomass further decomposes to produce combustible gases such as hydrogen and methane. These gases have a high calorific value and can be used as energy or further processed.

Liquid by-products

Wood vinegar: During the pyrolysis of biomass, a liquid rich in organic compounds such as acetic acid, methanol, and tar is produced, which is usually called wood vinegar. Wood vinegar has many uses, such as plant growth regulators and soil conditioners. Tar: Tar is a viscous liquid produced during the pyrolysis of biomass, mainly composed of aromatic compounds. The production and properties of tar depend on the type of raw materials and pyrolysis conditions. Tar can be used as a chemical raw material or fuel

Other by-products

Ash: The inorganic minerals originally contained in the biomass will remain during the pyrolysis process to form ash. The content and composition of ash depend on the type and nature of the raw materials.

Incompletely carbonized biomass: During the pyrolysis process, if the temperature is not high enough or the time is not long enough, part of the biomass may not be completely carbonized, forming incompletely carbonized biomass. These substances need to be further processed or used for other purposes.

It should be noted that the type and amount of by-products produced during the preparation of biochar will be affected by many factors, including the type of raw materials, pyrolysis temperature, time, pressure, and reaction atmosphere. Therefore, in actual production, it is necessary to select appropriate preparation methods and operating conditions according to specific circumstances to maximize the yield and quality of biochar, and reasonably handle and utilize the by-products produced.