torrefikaation

Torrefaction, sometimes written torrefikaation in certain languages, is a thermochemical conversion of biomass at moderate temperatures in a limited-oxygen environment. The process is typically conducted at about 200 to 300 degrees Celsius for a short residence time, often 0.5 to 2 hours. Under these conditions, moisture and a portion of the volatile organic compounds are driven off, producing a stable solid called torrefied biomass or bio-coal. The product has properties intermediate between raw biomass and coal and is easier to handle, transport, and store.

The torrefaction environment is designed to minimize combustion; the atmosphere is inert or reducing to prevent full pyrolysis or ignition. Physically and chemically, torrefaction lowers moisture and oxygen content while increasing carbon concentration, resulting in higher energy density and improved grindability. The material becomes more hydrophobic and less prone to moisture uptake, which aids storage and transport. Depending on the feedstock and process conditions, the mass yield is typically in the range of 60 to 90 percent of the original biomass.

Applications for torrefied biomass include co-firing with coal in power plants, production of uniform pellets for easier handling, and serving as a feedstock for gasification or other thermochemical pathways. Torrefaction offers potential logistic and energy-benefit advantages by reducing moisture, increasing energy content, and enhancing stability, though overall sustainability depends on feedstock type, energy input, and end-use.