How is biochar produced?

How is biochar produced?

The concept of “biochar” first appeared in scientific literature in the work of the National Assembly of the American Chemical Society. The word was a composite of “bio” (biomass) and “semi-coke” (char). The biochar described in that work was obtained from sorghum grain seeds using the “triple reverse burning ChemChar” process.

Bio-char has a high carbon content and has a fine-grained texture. Currently, it is produced using pyrolysis processes. Pyrolysis is a thermal treatment of biomass in the absence of oxygen, so preventing its combustion. As a result of the process, a mixture of the following substances is obtained: biochar itself, bio-oil, and synthesis gas.

The specific yield ratio of these pyrolysis products depends directly on the conditions of the process itself: temperature conditions, residence time and heating rate. These parameters can be optimized to obtain a specific product. Temperature from 400 to 500 °C (673-773 K) is used for the production of semi-coke. Temperatures above 700 °C (973 K) favour the release of liquid and gaseous components.

The pyrolysis process at higher temperatures is very fast. As a result, as a rule, we get 60% of bio-oil, 20% of bio-coal and 20% of synthesis gas. Slow pyrolysis, that is, the use of lower temperatures, leads to a higher percentage of semi-coke (~ 35%). This can be used to improve soil fertility (terra Preta).

Equipment for producing high-quality biochar – continuous charcoal kiln BIO-KILN