Microwave-Assisted Pyrolysis of Biomass Waste: A Mini Review

Abstract

The utilization of biomass waste as a raw material for renewable energy is a global concern. Pyrolysis is one of the thermal treatments for biomass wastes that results in the production of liquid, solid and gaseous products. Unfortunately, the complex structure of the biomass materials matrix needs elevated heating to convert these materials into useful products. Microwave heating is a promising alternative to conventional heating approaches. Recently, it has been widely used in pyrolysis due to easy operation and its high heating rate. This review tries to identify the microwave-assisted pyrolysis treatment process fundamentals and discusses various key operating parameters which have an effect on product yield. It was found that several operating parameters govern this process such as microwave power and the degree of temperature, microwave absorber addition and its concentration, initial moisture content, initial sweep gas flow rate/residence time. Moreover, this study highlighted the most attractive products of the microwave pyrolysis process. These products include synthesis gas, bio-char, and bio-oil. The benefits and challenges of microwave heating are discussed.

Microwave-assisted hydrothermal treatments for biomass valorisation: a critical review

“…Microwave-assisted hydrothermal treatment (MA-HTT) can also be used for the production of value-added chemicals and biomaterials. 130 As described above, the use of microwave heating to achieve hydrothermal conditions has several advantages over conventional heating, primarily including time and energy savings and higher products yields. 80,128 During the MA-HTT, biomass decomposes into valuable water-soluble compounds, which can be used in a plethora of applications.…”

“…An increase in microwave power produces higher power densities, increasing production rates and diminishing associated energy production costs. 130 Thangavelu et al 138 found that the highest glucose yield (43.8%) was obtained with high microwave power (900 W) during the MA-HTT of sago pith using carbon dioxide as a catalyst. In another study, these authors also proved that an increase in the microwave power exerted a positive effect on the glucose yield using H 2 SO 4 ; however, when HCl was used as a catalyst, the microwave power had a negligible effect.…”

“…As such, the microwave power must be carefully controlled to avoid both the degradation of sugars and unnecessary energy processing costs. 130 Given these antagonistic influences, several authors have concluded that the best combination for glucose production consisted of high microwave powers combined with short irradiation times. 33,134,140,150…”

Conversion of Lignocellulosic Biomass to Reducing Sugars in High Pressure and Supercritical Fluids: Greener Alternative for Biorefining of Renewables

“…[ 11,12 ] Conventional pretreatment methods are classified into biological (e.g., fungal and bacterial pretreatment), physical (e.g., milling, ultrasonic, microwave, mechanical extrusion); chemical (e.g., acid hydrolysis, alkaline hydrolysis, organosolv, oxidation delignification, ozonolysis), physicochemical pre‐treatment (e.g., steam explosion, ammonia fiber explosion) methods. [ 11–14 ] Emerging technologies are developed based on the use of ionic liquids (ILs), [ 15 ] deep eutectic solvents (DES), [ 16 ] microwave‐assisted methods, [ 17 ] sub/supercritical fluids (SCFs), [ 18,19 ] aiming at enhancing the recyclability of solvents/reagents of pretreatment processes. [ 15,20–22 ] These advanced solvents are recyclable and have high selectivity for removing noncellulosic fractions of the LC biomass.…”

Torrefaction and Pelleting of Wheat and Barley Straw for Biofuel and Energy Applications

“…Khelfa et al (2020) reported that microwave-assisted pyrolysis of pinewood sawdust mixed with activated carbon improved biomass heating, reduced energy consumption, and coproduct quality after the treatment. Also, Ethaib et al (2020) reported that microwave absorbers could adjust product distribution, improve bio-oil, biochar, and bio-gas at different treatment conditions, including the energy efficiency of the process. Biochar is a solid material produced from the thermochemical decomposition or carbonization of biomass.…”