Pyrolysis of pistachio shell, orange peel and saffron petals for bioenergy production

This study reports a detailed characterization of the slow pyrolysis fractions obtained from three major agricultural waste at temperatures of 300–550 °C with different origin and composition, namely pistachio shell (PS), bitter orange peel (OP) and saffron petals (SP). The liquid phase is the main fraction for PS, while SP gives rise to the highest amounts of solid and gas. C5-derived furans are promoted with SP, while OP is better suited for the obtention of aldehydes and ketones. PS delivers phenols-derived compounds, but also shows the highest acidity. Higher aromatic and ketones content is obtained increasing the pyrolysis temperature, at the cost of the furans fraction. Energy content of gas and solid fractions increases for all biomasses with pyrolysis temperature. Their highest heating values are obtained for PS at 550 °C, while the most promising biochar is achieved from SP, revealing high amounts of nitrogen and inorganic matter.