Effect of chemical treatment on thermal degradation behavior of litchi seed biomass

Litchi tree is planted in several countries of the world for its juicy fruit. For the estimated total annual global litchi production of ~ 2.7 million tons, around ~ 0.54 million tons of seeds as well as a sizeable amount of skin are generated as waste. This renewable waste biomass can be effectively used as the feedstock for recovering energy and obtaining several value-added products. In the present work, the fuel and thermochemical characteristics and thermal degradation behavior of acid- and alkali-treated litchi seed biomass were systematically investigated and compared for the first time. The average and maximum rate of mass losses, peak temperature and pyrolysis factor had been evaluated to assess the reactivity of the treated biomass. It had been observed that acid and alkali treatments improved the higher heating value and changed the thermal degradation behavior. The thermogravimetric (TG)/differential thermogravimetric analysis (DTG) data obtained at the heating rates of 20, 25 and 30 °C min −1 were used to evaluate the kinetic and thermodynamic parameters using iso-conversional models of Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Tang and Starink. The Criado method had been used to elucidate the prevailing thermal degradation reaction mechanisms at different fractional conversions. The average activation energy of the acid-treated biomass increased, and that of the alkali-treated biomass decreased compared to that of the untreated biomass. Graphical abstract