A review of operating parameters affecting bio-oil yield in microwave pyrolysis of lignocellulosic biomass

摘要

The depletion of fossil fuels and the environmental concerns associated with their extraction and utilisation have heightened the need for alternative sustainable energy resources. Microwave-assisted pyrolysis (MAP) of biomass is one of the promising sustainable methods for the production of bio-oil and value-added chemicals. This conversion technique has been widely studied at lab-scale and has demonstrated good potential in producing bio-oils of high quality. The main objective of this review paper is to examine the main parameters that affect MAP yields, whilst assessing the options for optimising the identified parameters for maximum bio-oil production. The results show that factors such as pyrolysis temperature, microwave power, microwave absorbent type and catalysis greatly influence the bio-oil yield. Pyrolysis holding time, feedstock particle size, purging gas type and flowrate also affect the bio-oil yield, though to a lesser extent. It is also established that the MAP technique is highly scalable and has several environmental benefits. The review concludes that the interdependence of various factors must be studied in detail in order to optimise bio-oil yield. There is therefore a need to develop an optimised pilot scale MAP system in a bid to determine the techno-economic viability of upscaling the technology for commercialisation. The use of Response Surface Methodology (RSM) via the Central Composite Design (CCD) approach is recommended for the optimisation of MAP systems because it takes into account the interaction between the variables that affect bio-oil yield. This review could be used to guide future research related to the design, simulation, fabrication and operation of pilot scale MAP reactors.