Fast pyrolysis of biomass for energy and chemicals: technologies at pilot plant, demo-plant and commercial scale

Biomass materials can be transformed to a gas, a solid or a liquid by pyrolysis, the thermal decomposition in absence of oxygen. While the intention of slow pyrolysis is to produce mainly charcoal, fast pyrolysis is meant to convert biomass to a maximum quantity of liquids. Both processes have in common that the biomass feedstock is densified to reduce the storage space and transport costs. A more stable and cleaner intermediate energy carrier is obtained, which is quite uniform and well-defined. In this paper the principles of fast pyrolysis will be discussed, and the main technologies summarized (demo scale: fluid bed, rotating cone and vacuum pyrolysis; pilot plant: ablative pyrolysis). Possible product applications are discussed. General mass and energy balance are summarized, and some remarks on the economics added. Challenges for the coming years are i) improvement of the reliability of pyrolysis reactors and processes, ii) the demonstration of the oil‟s utilization in boilers, engines and turbines, and iii) the development of technologies for the production of chemicals and biofuels from pyrolysis oils. One important conclusion here is that not the oxygen content in the oil as such is to be reduced, but that the number of oxygen functionalities in the oil needs to be limited