An investigation on the pyrolysis of the main residue of the brewing industry

Abstract

Brewer's spent grain (BSG) is the main by-product of the brewing industry. In this work, the pyrolysis of BSG using a fixed bed reactor was studied with respect to the valorization of this residue. The effects of the heating rate (10-50 °C/min) and temperature (450-650 °C) on the yields of pyrolysis products and on the physicochemical properties of the main products were quantified. The highest liquid yield (60.7%) was obtained at the pyrolysis temperature of 650 °C with a heating rate of 30 °C/min. The highest char yield (29.3%) was obtained at 550 °C and at heating rate of 10 °C/min. The results showed that high heating rates suppress dehydration reactions and favor bio-oil production. The produced biochar showed good potential for fuel application due to its high heating value (HHV) (27.1–28.3 kJ/g), moderate ash content (11.5%) and low sulfur content (<0.6%). The produced bio-oil contained phenols and ketones, which are precursors of several compounds used in the chemical industry, as well as pyrazines that are used in the pharmaceutical industry.