Biomass pyrolysis technologies for value-added products: a state-of-the-art review

Abstract

Biomass pyrolysis has been the focus of study by several researchers as a viable means of producing biofuels and other useful products. This paper gives a comprehensive, elaborate and updated review of pyrolysis technology as an efficient thermochemical route for biomass conversion. Pyrolysis products include pyrolytic gas, bio-oil, and solid biochar. Depending on the operating conditions, pyrolysis is usually classified as slow, intermediate, fast, and flash pyrolysis. The utilization of special catalysts can help facilitate pyrolytic gas production, while specific pretreatment processes can help facilitate bio-oil production. The efficiency of the pyrolysis process is affected by a number of factors such as temperature, heating rate, residence time, particle size, biomass type, and biomass pretreatment method. In this review, thermogravimetric analysis and kinetic modelling of biomass pyrolysis were also emphasized while the various constraints encountered during biomass pyrolysis have been highlighted and suggestions made to address them. More recently, more advanced experimental methods have been developed for biomass pyrolysis research, and these include Py-GC–MS/FID, TG-MS/TG-FTIR, in situ spectroscopy for reaction progress analysis, isotopic labelling, and intermediate product analysis techniques that enable the monitoring of the biomass devolatilization process as well as identification of the functional groups of the volatiles and monitoring of the changes in the functional groups on the surface of biomass in the course of pyrolysis. No doubt, biomass pyrolysis will continue to provide several benefits and serve as a sustainable means of producing biofuels, biochemicals, and other valuable products with far-reaching areas of applications.