Review of microwave-assisted lignin conversion for renewable fuels and chemicals

Energy insecurity and resource shortage are driving societies to look for sustainable and renewable energy and resource supplies. Thus, converting biomass into useful energy and chemical products has attracted considerable attention in the past decades. As a carbon-rich renewable biomass source, lignin has been extensively studied as a raw material to produce bioenergy and value-added chemicals. Fuel gas and phenolic products can be obtained by converting lignin. This study strives to extensively review recent developments in the microwave-assisted pyrolysis and solvolysis of lignin. Lignin structural components and extraction techniques are described under different conditions. In addition, the fundamentals and advantages of microwave heating technology and the background of lignin pyrolysis and solvolysis are presented. The effectual parameters of the microwave-assisted pyrolysis and solvolysis of lignin and their advantages are also summarized. This review concludes that microwave-assisted technology is an effective method for significantly reducing reaction time and improving the yields and selectivity of target products. In the future, low-cost catalysts and microwave-assisted conversion units need to be developed to achieve large-scale production of renewable fuels and value-added chemicals from lignin.