Comparative life cycle assessment of early-stage technological layouts for brewers' spent grain upcycling: A sustainable approach for adding value to waste

Abstract

Brewers' spent grain (BSG) is a promising agro-industrial residue for future biorefinery applications. Processes for extraction of protein and production of volatile fatty acids (VFAs) have been investigated for BSG upcycling. However, these technologies are still in an early stage of development, with very few comparative studies addressing environmental aspects. This study compares the traditional use of BSG as animal feed and three early-stage technological platforms using this material, from a life cycle analysis (LCA) perspective. The products in the platforms evaluated were as follows: VFAs, biogas, and biofertilizer (platform 1); proteins, biogas, and biofertilizer (platform 2); and proteins, VFAs, biogas, and biofertilizer (platform 3). The LCA modeling employed Easetech 3.4.4, with ReCiPe 2016 for the impact assessment. Platform 2 presented the lowest emissions in the global warming category (2.4 kg CO2-eq). For platform 3, the inclusion of isolated soy protein resulted in a greater reduction in carbon emissions (−53.9 kg CO2-eq), compared to the inclusion of VFAs (−3.0 kg CO2-eq). Therefore, future studies should prioritize the improvement of anaerobic digestion efficiency for VFAs production. Prospective LCA proved to be essential for identifying hotspots and guiding early optimization in technological development, increasing the chances of the developed technology becoming commercially viable and reaching the marketplace.