Application of brewers’ spent grains as an alternative biomass for renewable energy generation in a boiler combustion process

Abstract

In most industries that generate consumer products the main source of electrical energy comes from burning wood or fossil fuels in boilers. However, the use of these non-renewable fuels poses a huge problem for the current energy matrix and for the environment, which makes new alternatives necessary for a more environmentally friendly scenario. In view of this, our study evaluated the application of brewers’ spent grains (BSG) as an alternative biomass for energy generation in an industrial cogeneration system. For this, different blends of BSG and eucalyptus wood chips were used for steam generation. In addition, the effect of two different dehydration conditions on the drying kinetics of BSG were evaluated. The BSG presented an initial moisture content of 77.68%, 0.52% ash, mean particle size of 0.28 mm, density of 113 kg m–3, and lower calorific value of 17.84 MJ kg–1, making it suitable for energy recovery in a cogeneration system. Outdoor drying under external conditions can be applied to remove the moisture content from BSG, which is a low-cost strategy for further application in the drying process. From the biomass blends, the use of 80% BSG and 20% wood chips promoted better characteristics for application as fuel in a cogeneration system. The use of BSG promoted a reduction in the use of wood chips as fuel and generated a savings of approximately 9 thousand USD annually for the simulated system (80% BSG and 20% wood chips), a reduction of 82% of the cost, when comparing with a system using only wood chips. Therefore, the biomass by-product generated from beer production can be used to produce renewable energy in a cogeneration system, replacing the use of wood chips. The waste-to-energy strategy evaluated in this study can be a promising alternative for a circular economy transition, reducing the waste generated in breweries and promoting the recovery of renewable energy that can be applied in situ, making the entire industrial system become a biorefinery, using its main waste as biofuel to generate clean energy, promoting an energy transition to an increasingly cleaner energetical matrix.