Green coal, also known as bio-coal, is a type of fuel derived from contemporary processes involving biomass
rather than relying on the slow geological processes associated with the formation of traditional fossil fuels
such as oil. Unlike conventional fossil fuels, which contribute to carbon emissions, green coal is considered a
more environmentally friendly alternative.
The term "biomass" is often used interchangeably with "bio-fuel," though biomass typically refers to the
biological raw material used in the production of the fuel. This can include a variety of sources, such as wood
logs, agricultural residues, or waste plants. The end product of these biomass conversion processes is a
thermally or chemically altered solid substance, like torrefied pellets or briquettes, collectively referred to
as bio-coal.
The transformation of biomass into bio-coal involves a specialized process known as pyrolysis, conducted in an
inert environment devoid of oxygen and at elevated temperatures. This method, sometimes referred to as
torrefaction based on the temperature and end product characteristics, is frequently implemented using an
indirect-fired rotary kiln. The efficiency of biomass conversion to bio-coal depends on the specific attributes
of the source material.
Typically carried out at temperatures ranging from 500 to 800ºF and with a specific retention time, the biomass
undergoes a controlled pyrolytic decomposition to yield the bio-coal product. Within the rotary kiln, low btu
hydrocarbons are expelled, and these can be harnessed for combustion, providing the necessary heat for the
drying phase of biomass processing. This dual-purpose approach enhances the overall energy efficiency of the
bio-coal production process.
