Clean recovery of phenolic compounds, pyro‑gasifcation thermokinetics, and bioenergy potential of spent agro‑industrial bio‑wastes

FERNANDEZ, ANABEL; SETTE, PAULA A.; ECHEGARAY, MARCELO; SORIA, JOSÉ; SALVATORI, DANIELA; MAZZA, GERMÁN; RODRIGUEZ, ROSA

Biomass Conversion and Biorefinery

Springer

Año: 2022

The sequential process of polyphenol extraction from agro-industrial bio-wastes and pyrolysis/gasifcation of the residual solid fraction (RSF) constitutes an upgrading of the bio-waste to fuel and chemicals processes in the frame of the biorefnery conception. This process can be conducted based on sustainability concepts for bio-waste management, following the premises of the circular economy and the objective of reaching almost zero waste conditions. After the extraction process of apple pomace, grape marc, and grape stalk bio-wastes, three extracts rich in sugar, organic acids, and bioactive compounds were obtained. The polyphenol content was higher in extracts from grape wastes (4990±55 mg gallic acid/100 g in grape marc and 6997±70 mg gallic acid/100 g in grape stalk). However, the apple pomace extraction process was more efcient, since the RSF did not exhibit residual antioxidant capacity. The pyro-gasifcation kinetics of the RSF was investigated. The results indicated that the Flynn?Wall?Ozawa method presented the best R2, RSME, and SSE values. The Coats?Redfern method was applied to determine the reaction mechanism. For both pyrolysis and gasifcation processes, it was found that the frst-order reaction and three-dimensional difusion (Ginstling?Brounstein) models properly described the second and third process stages, respectively. The resulting values of the thermodynamic parameters, ΔG, ΔH, and ΔS, were 148.55 kJ/mol, 73.66 kJ/mol, and−0.11 kJ/K mol, respectively, for pyrolysis and 110.91 kJ/mol, 105.44 kJ/mol, and−0.01 kJ/K mol for gasifcation, respectively. According to bioenergy indicators, the RSF from the three bio-wastes had acceptable characteristics as a biofuel feedstock.