Optimization of Microwave Pyrolysis of Sugarcane Bagasse for Higher Energy Recovery and Soil Nourishment

Abstract

Agro-industrial sectors generates huge tonnes of surplus residues every year which being burnt unjudiciously causes environmental pollution. Exploitation of the various agricultural residues and exploration of different biomass conversion techniques to produce value added products and bioenergy constitutes the biorefinery in a strategic way that ultimately fits in a circular bioeconomy. Microwave pyrolysis has garnered significant attention over years due to faster heating rate, and its process efficiency over the conventional method. However, the impact of optimized product on the energy recovery and assessment of process factors on the biochar quality for agricultural applications with respect to the conventional process is seldom analysed. To delineate an optimized process for the superior biochar production through microwave pyrolysis intended for higher energy recovery with better soil amending potential, the present study aimed at analyzing the influence of operating variables on the biochar yield and product quality. Response surface methodology approach with Box-benken design considering influencing variables like the microwave power (360-720 W), time (10-30 min), feedstock amount (20-60 g) and particle size (150 – 1180 µ) were optimized to achieve the maximal biochar yield. The data was found to best fit into the second order quadratic regression model as indicated by the smaller p value and higher regression coefficient. Among the analyzed factors, the microwave exposure time was found to be the most influential factor. The interactive effects of residence time and the microwave power profoundly influenced the biochar yield and its qualitative properties. The maximum yield of microwave derived sugarcane bagasse biochar is found to be 42.3% obtained under optimal conditions of microwave power of 720 W for 43 mins of processing 20 g of biomass having particle size of 1500 µ. The characteristics of microwave derived biochar was found to be better compared to the conventionally produced biochar. This study provides a framework for multifunctional biochar production through microwave pyrolysis of sugarcane bagasse to obtain bioenergy and to improve the soil fertility making the process sustainable.

The qualitative properties of biochar were improvised upon optimization of microwave pyrolysis operational conditions. The experimental conditions for biochar yield, calorific value and cation exchange capacity were found to agree well with those predicted by the model. The physicochemical properties of the microwave produced biochar with intricately porous structure is expected to enhance its ion exchange potential aiding the better agricultural productivity and energy recovery. Such studies are necessary for unleashing the potential of microwave pyrolyzed biochar for sustainable circular bioeconomy based applications.