Comparative Characteristics and Potassium-Sulfur Release Behavior of Paddy Straw versus Banana Peduncle based Composite Biochar Produced by Co-pyrolysis with Phosphogypsum

Abstract

Co-pyrolysis of phosphogypsum and banana peduncle wastes was reported for the production of potassium-sulphur rich biochar composite fertilizer. However, large quantity of paddy straw are left out and fired on agricultural sites as waste, which required investigation for its alternative utilization for production of biochar composite. From this view, present work explored production of biochar composites from paddy straw mixed with phosphogypsum (4:1 ratio) by regulated co-pyrolysis process conditions such as temperature: 700°C; heating rate: 10°C/minute and residence time: 1 h for gaining biochar composite and also comparing physico-chemical characteristics, potassium-sulphur release behavior, kinetics with respect to banana peduncle mixed with phosphogypsum. Near neutral paddy straw (7.03) and alkaline banana peduncle biomass (8.53) converted into alkaline biochar (10.20 and 10.50) and composites (9.78 and 9.69) due to pyrolysis. The paddy straw biochar and composites retained relatively more carbon (%) i.e., 45.84 and 37.28 than banana based biochar 41.01 and 25.07. The phosphogypsum utilization enhances sulfur (6.65–7.66%) and calcium content (3.85–4.33%) in biochar composite. The potassium and sulphur leaching kinetic behavior fitted well with the second order kinetic model, indicating their slow-release aspect, which can contribute for long-term phyto-availability in soils.