Feedstock Sources: Wood chips, crop residues (corn stover, straw), poultry litter,
sewage sludge, nutshells, and more.
Mineral Composition: May contain potassium, phosphorus, calcium, and
magnesium depending on the source.
Synthetic Protocols for Biochar Production
The breakdown of organic biomass produces biochar, a carbon-rich substance with
a porous structure.
Different biochars were made using different feedstocks and manufacturing
methods, and the biochar’s physicochemical and surface characteristics were used
to determine its quality.
The char product is divided into three categories: charcoal, biochar, and
hydrochar.
The creation of biochar through pyrolysis, torrefaction, gasification, hydrothermal
liquefaction, and other methods is covered in depth.
1. Pyrolysis
In the absence of oxygen, pyrolysis is a thermal process that breaks down biomass
to create biochar (pyrochar), bio-oil, and gases.
It is divided into thermal, solar, infrared, and microwave heat sources, as well as into
slow, fast, and intermediate pyrolysis operating conditions, and it takes place at
temperatures exceeding 300°C.
Depending on the kind of biomass—typically cellulose, hemicellulose, and lignin—
the process entails intricate processes like depolymerisation, dehydration, and
aromatization.
Biochar that works well as fuel comes from lignocellulosic biomass, whereas
nonlignocellulosic biomass is better for soil modifications.
Nutrient content is improved by copyrolysis (e.g., seaweed and corn straw).
The output of microwave pyrolysis ranges from 12% to 75%, and it provides quicker,
more effective heating and produces high-quality biochar with a larger surface area
and pore volume.
Pyrolysis is a common method for creating biochar, which has many uses in energy
production, soil enhancement, and heavy metal adsorption.
2. Hydrothermal Liquefaction (HTL)
Wet biomass, such as sewage sludge, municipal garbage, algal residue, and
lignocellulosic materials, is transformed into bio-oil, gas, and hydrochar in water by
hydrothermal liquefaction (HTL), a thermochemical process that occurs at high
temperature and pressure.
Hydrothermal carbonization (HTC) under subcritical circumstances produces
hydrochar, which has distinct characteristics from biochar.
In a complex, interconnected network, the process involves reactions like
hydrolysis, dehydration, decarboxylation, and aromatization.
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