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===Chemical-physical properties of biochar=== | ===Chemical-physical properties of biochar=== | ||
The properties of biochar vary depending on the feedstock and conditions, primarily the pyrolysis temperature, under which the biochar is produced. Consequently there is considerable variability in the chemical and physical properties of different biochars. The table below summarizes data from our literature review. Some conclusions from the literature are summarized below. | The properties of biochar vary depending on the feedstock and conditions, primarily the pyrolysis temperature, under which the biochar is produced. Consequently there is considerable variability in the chemical and physical properties of different biochars. The table below summarizes data from our literature review. Some conclusions from the literature are summarized below. | ||
+ | *'''Biochar has a large surface area.''' | ||
*'''Cation exchange capacity (CEC) decreases as pyrolysis temperature increases'''. This is due to the loss of volatile organic content and associated functional groups as temperature increases. As CEC decreases, the ability of biochar to retain negatively charged chemicals, such as phosphate, decreases. | *'''Cation exchange capacity (CEC) decreases as pyrolysis temperature increases'''. This is due to the loss of volatile organic content and associated functional groups as temperature increases. As CEC decreases, the ability of biochar to retain negatively charged chemicals, such as phosphate, decreases. | ||
*'''Non-wood vegetative feedstocks have a greater CEC than wood feedstocks.''' This is due to a greater percentage of aliphatic compounds and associated functional groups. Non-wood feedstocks primarily consist of grasses. | *'''Non-wood vegetative feedstocks have a greater CEC than wood feedstocks.''' This is due to a greater percentage of aliphatic compounds and associated functional groups. Non-wood feedstocks primarily consist of grasses. |
Biochar is a charcoal-like substance that’s made by burning organic material from biomass in a controlled process called pyrolysis. Biomass waste materials appropriate for biochar production include crop residues (both field residues and processing residues such as nut shells, fruit pits, bagasse, etc), as well as yard, food and forestry wastes, and animal manures. Clean feedstocks with 10 to 20 percent moisture and high lignin content must be used. Examples are field residues and woody biomass. Using contaminated feedstocks, including feedstocks from railway embankments or contaminated land, can introduce toxins into the soil, drastically increase soil pH and/or inhibit plants from absorbing minerals. The most common contaminants are heavy metals—including cadmium, copper, chromium, lead, zinc, mercury, nickel and arsenic, and Polycyclic Aromatic Hydrocarbons (PAHs).
Biochar is black, highly porous, lightweight, fine-grained and has a large surface area. Approximately 70 percent of its composition is carbon. The remaining percentage consists of nitrogen, hydrogen and oxygen among other elements. Biochar’s chemical composition varies depending on the feedstocks used to make it and methods used to heat it.
Biochar benefits for soil may include the following.
Biochar is also found to be beneficial for composting, since it reduces greenhouse gas emissions and prevents the loss of nutrients in the compost material. It also promotes microbial activity, which in turn accelerates the composting process. Plus, it helps reduce the compost’s ammonia losses, bulk density and odor.
The properties of biochar depend on the feedstock and the conditions under which the biochar is produced.
NOTE - this is from one study, just inserted here as an example
NOTE - this is from one study, just inserted here as an example
This section is divided into chemical-physical properties, hydraulic properties, retention-leaching properties, and other properties.
The properties of biochar vary depending on the feedstock and conditions, primarily the pyrolysis temperature, under which the biochar is produced. Consequently there is considerable variability in the chemical and physical properties of different biochars. The table below summarizes data from our literature review. Some conclusions from the literature are summarized below.
Chemical and physical properties of biochar.
Link to this table
Property | Range found in literature1 | Median value from literature |
---|---|---|
Total phosphorus (%) | 0.0061 - 1.086 | 0.0618 |
Total nitrogen (%) | 1.2 - 2.4 | 0.88 |
Total potassium (%) | 0.0079 - 1.367 | 0.181 |
Total carbon (%) | 24.2 - 90.9 | 66 |
Total hydrogen (%) | 0.67 - 4.3 | 2.8 |
Total oxygen (%) | 2.69 - 28.7 | 16.3 |
pH | 6.43 - 10.4 | 9.66 |
Cation exchange capacity (cmol/kg) | 0.1 - 562 | 43.1 |
Surface area (m2/g | 2.78 - 203 | 30.6 |
Electrical conductivity (μs/cm) | 100 - 2221 | 231.5 |
Pore volume (cm3/g) | 0.006 - 0.51 | 0.036 |
Total calcium (%) | 0.0954 - 3.182 | 0.590 |
Total magnesium (%) | 0.0297 - 0.2801 | 0.0587 |
Total copper (%) | 0.0001 - 0.0078 | 0.00025 |
Total zinc (%) | 0.0002 - 0.0152 | 0.00135 |
Total aluminum (%) | 0.001 - 0.1929 | 0.0290 |
Total iron (%) | 0.0009 - 0.2209 | 0.0333 |
Total manganese (%) | 0.0001 - 0.1025 | 0.00145 |
Total sulfur (%) | 0.01 - 0.44 | 0.05 |
Primary references for this data:
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