Life Cycle Assessment of Polylactic Acid/Brewer’s Spent Grain Biocomposites: Environmental Impact of Lignocellulosic Waste Incorporation

The environmental burden of conventional plastic packaging has increased interest in sustainable alternatives. This study evaluates the environmental performance of polylactic acid (PLA) biocomposites reinforced with brewer’s spent grain (BSG), an agro-industrial by-product, using life cycle assessment (LCA). PLA, PLA/BSG biocomposites containing 10 wt% and 20 wt% BSG, and conventional plastics (polypropylene and polyethylene terephthalate) were compared. BSG was modeled using a cut-off approach as a waste-derived material, with preparation impacts attributed to energy consumption. Cradle-to-gate results showed environmental benefits from BSG incorporation, but also relevant trade-offs. Compared with neat PLA, 10 wt% and 20 wt% BSG reduced global warming potential by 4.10% and 8.20%, respectively, and fossil depletion by 5.40% and 10.70%. In contrast, freshwater eutrophication increased with BSG content, reaching +32.2% at 20 wt% BSG, mainly due to electricity consumption associated with drying and milling. Compared with conventional plastics, PLA/BSG biocomposites showed substantially lower fossil depletion, although polypropylene had a lower global warming potential. Composting and recycling performed better than incineration. Overall, BSG incorporation can reduce fossil-resource dependence and support circular resource utilization, while optimization of BSG processing is needed to minimize environmental trade-offs.