Process development status of fast pyrolysis technologies for the manufacture of renewable transport fuels from biomass

Fast pyrolysis is a promising thermochemical method of producing renewable fuels and chemicals from biomass and waste feedstocks. There is much interest in optimising the choice of feedstock pre-treatments, reaction conditions, reactor designs, and catalysts as well as product upgrading steps to improve the techno-economic feasibility of the process. This article summarizes the current state-of-art in thermal and catalytic fast pyrolysis and outlines the major considerations for process development. The status of process technologies and development efforts on thermal and catalytic fast pyrolysis are reviewed, with a focus on efforts producing bio-oil for use in manufacturing transport fuels or fuel blends as the final product. The leading thermal pyrolysis processes, which use circulating, bubbling, auger screw and rotating cone reactor technologies, are reviewed alongside recent research and development activities on catalytic fast pyrolysis. This review finds that several technologies for thermal fast pyrolysis are operating at commercial scale, while integrated process development efforts are just starting to focus on applying catalytic fast pyrolysis at pilot scale. Processes for catalytic fast pyrolysis, either via in-situ or ex-situ upgrading of the bio-oil vapours is an area currently receiving significant research and development interest. This processing route may enable the production of partially upgraded bio-crudes which are suitable for processing to final fuel products in centralized bio-refineries or for co-processing in petroleum refineries. However, there remains a lot of fundamental and laboratory work to be done to develop deeper understanding of the processes, so that the catalysts and reaction conditions can be optimized. New combinations of unit operations and possibly novel reactors will likely be required to economically convert biomass feedstocks into partially upgraded bio-crudes. Techno-economic assessment shows that biofuels from fast pyrolysis may be competitive with petroleum fuels in future, however there are currently only a handful of plants operating commercially.