Pyrolysis in auger reactors for biochar and bio-oil production: A review

Pyrolysis is the thermochemical decomposition of biomass under oxygen-limiting conditions used for biochar and bio-oil production. Depending on biomass feedstock, pyrolysis technology and operating parameters, product yields and properties will differ. Among the available pyrolysis units, auger pyrolysis is a polyvalent and promising technology for producing both bio-oil and biochar. These reactors are simple to operate and can be mobile, they require little or no carrier gas and low energy. Moreover, the operating parameters can be controlled easily in order to obtain the desired products. Recently, many research articles on biomass pyrolysis in auger reactors have been published. Design of laboratory-scale pyrolysis units and operating parameters differ considerably. Therefore, there was a need to list the studies in which auger pyrolysis reactors are used and to collect data for experimental operating parameters and product yields. The type and the capacity of the reactor, pyrolysis temperature, solid residence time, carrier gas flowrate, vapour residence time, and biomass feedstock type and size were identified as the parameters having the most influence on product yields and their properties. Because each pyrolysis reactor is unique, it is important to establish the relationship between operating parameters and product yields and their properties for each biomass feedstock. Future work is needed in order to provide simple solutions to scale-up laboratory-scale auger pyrolysis units to industrial size.