Slow pyrolysis of coconut shells for bio-char production: optimization of process parameters and product characterization

Agro-waste and agro-industrial waste has become problematic pollution sources as this waste is dumped or burnt directly, contributing to greenhouse gases, a severe environmental threat. Pyrolysis is a promising technique for converting any ligno-cellulosic biomass into valuable products such as bio-oil, biochar, and pyrolysis gas. Pyrolysis process parameters such as temperature, heating rate, holding time, particle size, reactor-to-raw material volume ratio, and agitation were studied. The process parameters were optimized using response surface methodology (RSM) for biochar as a primary product. The biochar yield and its fixed carbon content were considered the responses/outputs for the optimization, as these properties will change with the selected process parameters. Coconut shells were used as a raw material and experiments were carried out over the temperature range of 300 °C to 500 °C with a heating rate ranging from 2.5 °C/min to 12.5 °C/min and holding time from 30 min to 90 min, ensuring slow pyrolysis conditions. It was observed that only temperature has a significant effect on product distribution and composition