Pyrolysis of Amaranth Inflorescence Wastes: Bioenergy Potential, Biochar and Hydrocarbon Rich Bio-Oil Production

Abstract

Many agro-industrial companies grow amaranth for the subsequent production of amaranth oil, flour, cereals, flakes, and bran. After the grain is extracted, waste in the form of inflorescences remains, which can be used to obtain useful new products. This work investigated the use of pyrolysis to recycle amaranth inflorescence wastes (AIW). Thermochemical conversion experiments in an inert medium were carried out in a laboratory setup at 550 °C and a heating rate of 10 °C/min. It was found that the AIW pyrolysis produced 37.1 wt.% bio-oil, 35.8 wt.% pyrogas and 27.1 wt.% biochar. The oil fraction of the obtained bio-oil contains 41.8% of hydrocarbons. Thermogravimetric analysis of AIW was performed in the temperature range from 40 to 1000 °C at heating rates of 10, 15, and 20 °C/min in argon medium (75 mL/min). The kinetic parameters were determined by the model-free Friedman, Ozawa-Flynn-Wall, and Kissinger-Akahira-Sunose methods. The average activation energy values are in the range of 208.44–216.17 kJ/mol, and they were used to calculate the thermodynamic parameters. The results indicate that the pyrolysis application will allow efficient conversion of AIW into value-added products.