Biomass fast pyrolysis is a thermal process during which the raw materials are heated rapidly at to a temperature range between 450-500 °C, in the absence of oxygen. Under these conditions, biomass is converted to organic compounds vapors, non-condensable gases and liquid tar. The organic vapors are thereafter condensed, thus producing the pyrolysis oil or bio-oil. In common practice, about 50-75% of the initially fed raw material weight is converted to bio-oil.
The remarkable advantage of this process is its ability to convert almost any kind of biomass into a homogenous, clean and renewable biofuels. Pyrolysis oil may be used as a fuel for power production, as an automotive fuel or as chemicals raw material. Its energy density (the energy content that it has per unit of volume) is about 5 times higher than that of biomass feedstock, a fact that results to special management benefits (concerning its storage, transportation etc.). Thereby it can be easily transported from one area to another thus providing higher flexibility in the electric power grid and limiting the grid losses. Another additional benefit of pyrolysis oil is its ability to be fed to higher efficiency turbines.
A wide range of biomass feedstock can be used in the process. For achieving a desirable conversion rate, the pretreatment of biomass is essential, namely its grinding to small uniform pieces (<10mm) and its drying under a 10% moisture content. In a well-designed pyrolysis plant the required heat for the drying process should be covered by the plant itself (self-consumption) thus reducing its operational cost and enhancing its environmental footprint.
The advantages to which biomass pyrolysis process is connected has led to a dramatic increase in the research efforts around that scientific subject. The result of all these efforts is the appearance of the first commercial power production plant fueled with pyrolysis oil in Alberta, Canada. The project is on the stage of engineering and licensing and will process about 400 tonnes of woody biomass (sawdust and wood chips) each day. It is predicted that it will generate enough clean energy to cover the demands of 3.800 local residencies.