Helianthus tuberosus as a promising feedstock for bioenergy and chemicals appraised through pyrolysis, kinetics, and TG-FTIR-MS based study

Abstract

The Jerusalem artichoke (Helianthus tuberosus) is a perennial plant which is adapted to wide climatic conditions ranging from temperate to semiarid regions. Its tubers are alternative to potatoes and it can typically produce 18–28 tons of waste foliage from one hectare which can be exploited for bioenergy via pyrolysis. However, the pyrolytic behavior of its waste was never studied. The present study was focused to assess its potential via pyrolysis, kinetics, thermodynamics, and TG-FTIR-MS based study to produce energy and chemicals. The biomass was subjected to thermal degradation at five heating rates (10, 20, 30, 40, 80 °C/min) under an inert environment. The thermograms showed that the highest rate of thermal transformation was achieved at 270–430 °C. The data were subjected to kinetics and thermodynamics analyses using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Starink and Vyazovkin models. The activation energy (Ea) and pre-exponential factors remained consistent and ranged from 160 to 175 kJ/mol and 1012–1014 s−1 at conversion fractions ranging from α = 0.2 to α = 0.6. The kinetic parameters showed higher statistical confidence with R2 ≥ 0.98 and good agreement among the data obtained through various models. The high heating value (HHV = 18.76 MJ/kg), change in enthalpy (∼ΔH = 150–170 kJ/mol), and Gibbs free energy (ΔG = 158–168 kJ/mol) demonstrated the substantial bioenergy potential of this waste. Moreover, the pyrolytic gases were subjected to Thermogravimetric-Fourier Transformed Infrared Spectroscopy-Mass Spectrometry (TG-FTIR-MS) analyses to identify the nature of products. The detected functional groups showed that the evolved gases contained aldehydes, phenols, carboxylic acids, esters, aromatic hydrocarbons and methane which indicated the substantial potential of this waste to produce energy and chemicals via pyrolysis causing no competition with the food/feed or land for food/feed.