Experimental and feasibility study of bio-waste valorization through pyrolysis for energy and materials production in the concept of circular economy

Abstract

The pyrolysis and co-pyrolysis characteristics of large abundant bio-wastes, namely date pits (DP), peanut shells (PS), coffee grounds (CG), and tea waste (TW) were investigated in detail. The TG/DTG and pyrolysis procedures were used to examine the thermal pyrolysis behavior of these agro-wastes and their blends (50%CG/50%DP, 50%CG/50%PS, 50%DP/50%PS, 50%TW/50% DP,50%TW/50%PS and 50%CG/50% TW by weight). The characterization of these feedstock has shown their suitability for energy and material valorization. Experiments were carried out in a batch pyrolysis at a medium heating rate of 10 °C/min. The goal was to identify the best combination aiming to produce either char or hydrogen-rich gas, which can contribute to the development of the circular bio-economy. It was demonstrated that pyrolysis favored the liquid product, fluctuating from 34.31% (TW) to 50.92% (DP), while the co-pyrolysis greatly increased the gaseous product, which ranged between 42.02% (TW-DP) and 55.17% (PS-TW). The blending of CG and PS resulted in heightened reactivity, leading to an enhanced generation of H2 (34.44%). The optimal mixture was found to be CG-TW, showcasing superior performance in terms of gas quality (38.39% H2) and yield (53.74%). This outcome underscores the potential of CG and TW as a synergistic blend for efficient hydrogen-rich gas production. The FTIR findings revealed that the recovered biochars have the potential to serve as solid fuels, biofertilizers, or carbon materials. Additionally, they could be used as eco-friendly precursors for chemical and related industries. By analyzing various waste mixtures and their respective pyrolysis properties, this research aims to contribute to the development of sustainable waste management practices as well as efficient energy and material production methods.