Waste to energy: production of energy-dense solid biofuel from palmyra palm shell waste via optimization of torrefaction process parameters using response surface methodology

An energy-dense solid biofuel was produced with a heating value of 24.33 MJ/kg from Palmyra palm shell (PPS) waste (heating value 19.50 MJ/kg) under the optimal condition of 295.54 °C for 60 min. The optimized condition was obtained using a central composite design coupled with Response Surface Methodology, resulting in an energy yield of 62.30%, an energy density of 1.24 MJ/kg, and a fuel ratio of 1.30. The ANOVA confirmed the reliability of the quadratic model in predicting responses. The burnout time and burnout profile of torrefied PPS were comparable to those of high-ash Indian coals, as confirmed by TGA/DSC. FTIR spectroscopy confirmed the changes in the wavenumber of functional groups, while FE-SEM revealed alterations in surface morphology during the torrefaction process. GC-MS identified 24.05%, 5-chlorosalicylamide in the condensate, which serves as a snail-control drug and is also used as an intermediate compound for synthesizing anticancer drugs. The entire scheme ensures environmental sustainability and appears to be lucrative for solid biofuel production from Palmyra palm shell (PPS) waste.