Microwave pyrolysis of lignocellulosic biomass: Heating performance and reaction kinetics

Lignocellulosic biomass is an abundant renewable resource and can be efficiently converted into bioenergy and green materials by using microwave pyrolysis. In this study, microwave pyrolysis of seven biomass feedstocks (corn stover, rice straw, rice husk, sugarcane bagasse, sugarcane peel, coffee grounds, and bamboo) was studied. The maximum temperature of microwave pyrolysis was highly correlated with the combustible content of the feedstocks. The influence of microwave power level on both maximum temperature and heating rate was substantial. Either maximum temperature or heating rate had a linear relationship with microwave power level. However, there was a breakpoint at a power level of 250 W. Compared with conventional pyrolysis, microwave pyrolysis was faster and needed less input energy. Microwave pyrolysis provided higher weight losses than conventional pyrolysis, and this difference was more substantial at lower temperatures. Kinetic parameters of microwave pyrolysis at lower and higher microwave power levels were different. Reaction rates at higher microwave power levels can be higher than those at lower power levels by approximately one order of magnitude. Compared with conventional pyrolysis, the rate constant of microwave pyrolysis was much higher, and its activation energy and pre-exponential factor were much lower.