In the future, renewable energy technologies will have a significant role in catering to energy security concerns and a safe environment. Among the various renewable energy sources available, biomass has high accessibility and is considered a carbon-neutral source. Pyrolysis technology is a thermo-chemical route for converting biomass to many useful products (biochar, bio-oil, and combustible pyrolysis gases). The composition and relative product yield depend on the pyrolysis technology adopted. The present review paper evaluates various types of biomass pyrolysis. Fast pyrolysis, slow pyrolysis, and advanced pyrolysis techniques concerning different pyrolyzer reactors have been reviewed from the literature and are presented to broaden the scope of its selection and application for future studies and research. Slow pyrolysis can deliver superior ecological welfare because it provides additional bio-char yield using auger and rotary kiln reactors. Fast pyrolysis can produce bio-oil, primarily via bubbling and circulating fluidized bed reactors. Advanced pyrolysis processes have good potential to provide high prosperity for specific applications. The success of pyrolysis depends strongly on the selection of a specific reactor as a pyrolyzer based on the desired product and feedstock specifications.

Biomass pyrolysis is one of the beneficial sources of the production of sustainable bio-oil. Currently, marketable bio-oil plants are scarce because of the complex operations and lower profits. Therefore, it is necessary to comprehend the relationship between technological parameters and economic practicality. This review outlines the technical and economical routine to produce bio-oils from various biomass by fast pyrolysis. Explicit pointers were compared, such as production cost, capacity, and biomass type for bio-oil production. The bio-oil production cost is crucial for evaluating the market compatibility with other biofuels available. Different pretreatments, upgrades and recycling processes influenced production costs. Using an energy integration strategy, it is possible to produce bio-oil from biomass pyrolysis. The findings of this study might lead to bio-oil industry-related research aimed at commercializing the product.