Biochar, charcoal, and activated carbon are all generically characterized as follows:
Biochar is a carbon-rich solid generated from biomass (organic plant matter) cooked in a low-oxygen atmosphere. Biochar is meant for agricultural usage and is commonly used as a soil amendment, which is defined as any substance added to soil to enhance physical qualities such as water and nutrient retention.
Charcoal is a carbon-rich material that is similarly generated from biomass. Charcoal is typically used for heating or cooking and is connected with barbecuing.
Activated carbon is a carbon-rich material generated by pyrolysis from biomass or other carbonaceous substances such as coal or tar pitch. A carbon material is also "activated" during the process by procedures that dramatically expand the surface area of the material, allowing it to catch (or "adsorb") a greater number of molecules. Because of its high adsorption capacity, activated carbon is good at removing pollutants from water and air, which is why it is frequently used in remediation or purification operations.
Pyrolysis for the production of carbon-rich solids
The major thing they have in common is how they are made.
Biochar, charcoal, and activated carbon are all produced by pyrolysis, a process in which a source material—in this example, a carbon-containing substance—is subjected to high temperatures in the absence of oxygen, causing it to thermally breakdown into char or carbon-rich solids. The absence of oxygen is critical to the process because too much oxygen would oxidize the carbon and cause it to burn away as gaseous products. Pyrolysis allows you to customize a carbon-based product for a specific use by adjusting the starting material (or "feedstock") and processing conditions.
The quality of the beginning material can also influence its processing efficacy, final application, and environmental impact. Other biomass sources may include unknown biomass and materials gathered from municipal waste streams, for example.
Processing factors include pyrolysis temperature and duration, particle size, moisture content, and activation, which increases the porosity and surface area of the carbon material and enhances its efficacy.
Generally, one of two procedures is used for activation.
Steam activation is a physical process in which steam is used to remove carbon from already charred (or "carbonized") material at higher temperatures. To enhance the surface area of the carbon, the pores are opened.
Chemical procedures entail combining a raw material, such as wood, with a chemical, such as phosphoric acid, and then drying and carbonizing it. The chemical inhibits the resultant char from shrinking, resulting in a more porous structure.
On a chemical level, biochar, charcoal, and activated carbon can all be comparable. Each solid has several "aromatic carbons" that are tightly linked together and hence stable.
Carbon-rich materials may also contain components such as oxygen or nitrogen that were originally present in the parent material, as well as additional compounds, if the solids have been "loaded" with substances that would improve their performance in a given application.
The three forms of carbon differ primarily in their ultimate uses and source materials, as shown by their definitions.
Biochar is used in agriculture; charcoal is used in heating and cooking; and activated carbon is used in filtering and purification.
While all three may be derived from biomass, charcoal is most commonly linked with wood. Activated carbon may also be produced from non-biomass carbonaceous sources.