Biomethane generation and CO2 recovery through biogas production using brewers' spent Grains

Abstract

In Brazil approximately 13 billion liters of beer were produced in 2016. The massive production of beer goes hand in hand with the generation of a huge amount of waste during the production process; a greater part of this waste is composed of about 2.6 million tons of Brewers' Spent Grains (BSG) the main waste. Due to their organic characteristics and in order to reduce the environmental impacts caused by their improper disposal or treatment, these residues can be effectively treated in anaerobic systems. One of the products of anaerobic digestion is biogas; this gas contains methane (CH4) and dioxide carbon (CO2), and further other gases in lower concentrations; these include oxygen, hydrogen sulfide and hydrogen. When biogas is purified, it transforms into biomethane, which is rich in methane with high calorific value. The processes involving the purification of biogas lead to the simultaneous recovery of other gases, such as CO2 - which is used in the brewing industry. Using experimental assays, this work evaluates the biochemical methanogenic potential of BSG. The results obtained showed that nearly 82 m3CH4 t−1DM (Dry Matter) of biomethane can be produced from the substrate and about 29 m3CO2 t−1DM can be recovered from the substrate. Thus, beer production in Brazil can be used as a source of energy production and CO2 recovery. Our findings show that the reutilization of BSG can yield 76% of CO2 required in the brewing process; reducing in US $116 million in the costs incurred in the purchase of CO2.