Dielectric characterization of mustard (Brassica Nigra) husk (MSH) by investigating biomass-microwave interaction for energy storage applications

Generation of huge amount of agricultural waste and its inappropriate disposal may lead to various environmental, pollution and health related issues. Development of an efficient technique for the disposal or utilization of waste is needed. Biomass, in recent few decades, has become popular for the energy storage. Microwave pyrolysis is a prominent technique to produce highly carbonaceous porous char form solid waste. This char may be used in different applications including development of biomass-derived supercapacitor electrodes. Biomass-microwave interaction during microwave pyrolysis is crucial and it determines the efficacy and effectiveness of the microwave pyrolysis process. In the present study, dielectric properties of mustard husk (MSH) at two different frequencies (900 MHz and 2450 MHz) have been investigated within the temperature range of 30–600 °C. At 30 °C, the dielectric constant (ε′) of MSH is 3.275 at 900 MHz and 2.978 at 2450 MHz while the dielectric loss (ε′′) is 0.268 at 900 MHz and 0.311 at 2450 MHz. Within the studied temperature range (30–600 °C), ε′ and ε′′ values decreased by 42.41 % and 65.67 % at 900 MHz frequency while these lowered by 40.16 % and 61.73 % at 2450 MHz frequency. Penetration depth shows 102.01 % and 120.937 % rise on increasing the temperature from 30 to 600 °C for 900 MHz and 2450 MHz frequencies, respectively. Dielectric constant values were fitted to pre-existing Boltzmann and Gauss models. The study suggests that MSH interacts to microwave to a high extent and microwave pyrolysis is suitable to produce the energy rich product from agricultural wastes. The present study utilises novel approach of converting MSH into value added product. The novelty lies in the fact that MSH cannot be used in other alternative like animal feeding of crop fertilization etc. And burning huge amount of MSH in open environment creates hazardous environmental impact. Thus, MSH available largely may be contributes to energy storage application that eventually benefits the environment and use of renewable resources.