Microwave-assisted pyrolysis of agricultural residues: current scenario, challenges, and future direction

In the agricultural sector, huge quantities of agricultural residues are being generated every year. The valorization of the underutilized agricultural residues through microwave-assisted pyrolysis (MAP) is highlighted in recent years. This article focuses on the current status for MAP of agricultural residues with the possible applications of the pyrolysis products in the agricultural sector and the challenges to make the process more compatible, acceptable, and sustainable along with its future directions to gain more economic benefits even at small-scale applications. The findings of the studies undertaken by the various researchers reveal that the yields (biochar, bio-oil, and gas) obtained from the MAP vary according to feedstock and pyrolysis conditions. The product, biochar, has several applications proven successfully in the agriculture. Bio-oil product cannot be used directly either as a biofuel or in agriculture but wood vinegar, extracted easily and cheaply from it, can be utilized directly by the crop growers in farming. Wood vinegar has been proved to be a useful and environment-friendly product for many applications, particularly in the agriculture. The gas derived from MAP can also be used to operate the pyrolysis system or may be used as a biofuel especially for thermal energy applications in rural areas. Small-scale MAP plants may be economically viable and more favorable in the agricultural sector than the large-scale plants. Integrating other source of renewable energy, as an input power for operating the MAP process, may also be a better option to make the process more reliable, economic, and environmental friendly.