Production, characterization and evaluation of biochar from pod (Pisum sativum), leaf (Brassica oleracea) and peel (Citrus sinensis) wastes

Purpose Biochar has potential as a valuable tool for the agricultural industry with its unique ability to help build soil health, increase physical properties of soil, soil pH, organic carbon content, conserve water and mitigate drought, reduce GHG emission, conserve nutrients, decrease fertilizer requirements, sequester carbon, increase crop productivity and serve as a most preferred habitat for microbes. In this study, three perishable biomass wastes viz. Pea pod ( Pisum sativum ), cauliflower leaves ( Brassica oleracea ) and orange peel wastes ( Citrus sinensis ) were carbonized and characterized for differential application. Methods The biomass was subjected to carbonization at different temperatures from 100 to 600 °C for 1 h. Biomass and biochar samples were characterized for proximate (M, VM, FC, Ash), ultimate (CHNS-O), biochemical properties (Ce, He, Li), thermo gravimetric analysis, pH, EC and bulk density. The biochars were also analyzed through SEM and FTIR for identification of pore size and functional groups. Results The char yield was high in cauliflower leaf (30.16 %), followed by orange peel (25.54 %) and pea pod (21.154 %) at 300 °C. The total organic carbon (11.61 %), total negative surface anions (4.25 mmol H + eq/g C) and water holding capacity (200 %) were high in pea pod biochar. The SEM images of biochar samples showed plane cleavage surfaces with broken edges. The surface functional groups of all the three biochar samples were hydroxyl, methyl, carboxylic and alkene groups. Conclusion The pea pod and cauliflower leaf biochar showed higher values of organic carbon, total surface anions, water holding capacity and mineral content and performed as best soil amendment than orange peel biochar. These biochar can be used as an effective medium for increasing soil carbon, irrigation efficiency and efficient disposal of agricultural waste-biomass.