Optimization of pyrolysis process parameters for the production of biochar from banana peduncle fibrous waste and its characterization

Banana peduncle waste (BPW) is a major fibrous waste generated from the wholesale vegetable markets in urban areas that is less degradable due to the presence of cellulose, hemicellulose and lignin contents. In order to recover energy and produce biochar as a by-product, pyrolysis is a promising alternate method for the treatment and disposal of BPW. The novel aspect of the study is to use response surface methodology (RSM) with central composite design by Minitab Software to identify the optimum process parameters, such as pyrolysis temperature (PT), holding time (HT), and heating rate (HR) for the responses biochar yield (%), carbon content (g), and pH of the biochar. For RSM the minimum and maximum values are considered in the range of 400–600 °C, 80–240 min and 10–20 °C min⁻¹ for PT, HT and HR, respectively. Experiments of 20 sets at different parameters as per RSM were carried out in lab scale pyrolysis unit and results showed that PT and HT have a significant effect on biochar yield, carbon content and pH, while HR did not show a considerable impact. The proximate and ultimate analyses of BPW and biochar obtained (BPW–BC) were also investigated including SEM and FTIR. From the results, biochar yield of 50%, carbon content of 3.18 g and pH of 11 were obtained at optimum conditions of PT: 462 °C, HT: 80 min and HR-10 °C min⁻¹ and found that the experimental responses are very close to the predicted values. Further, the characteristics of BPW–BC obtained vary with process conditions and could be potentially used for various applications such as soil conditioners, adsorbent pyrogenic carbon capture and storage.