Prospective life cycle assessment of an integrated biorefinery for production of lactic acid from dairy side streams

Abstract

In Ireland, the world's first-of-a-kind integrated dairy biorefinery has been developed to address waste disposal challenges in the dairy industry by converting dairy side streams into high-value biochemicals, specifically lactic acid (LA). This study aims to assess the environmental impacts of this innovative technology at a commercial scale through a comprehensive life cycle assessment (LCA) study. Experimental data from a pilot-plant facility was scaled up to a production capacity of 20,000 tons of LA per year using SuperPro Designer®. This data was combined with information from upstream processes such as milk production, cheese production, and transport, using OpenLCA. The cradle-to-gate LCA revealed that milk production had the greatest overall impact across all categories. Enteric fermentation has the most significant impact on climate change, while fertilizer and concentrate feed production primarily contributed to non-renewable energy demand, ozone formation, human toxicity, water consumption and fossil depletion. Fertilizer application substantially influenced eutrophication, acidification and ecotoxicity indicators. However, scenario analysis showed that implementing strategies like substituting biorefinery byproducts with fossil-based products, increasing renewable energy penetration, and integrating dairy beef production could result in significant environmental savings across all impact categories. Moreover, the findings highlighted that the handling of co-products would determine the magnitude of the system's impact. This study concludes that combining process design analysis with accessible data at a higher Technology readiness level (TRL) 7 offers an opportunity to identify hotspots and recommend alternative strategies to improve the environmental sustainability of the whole system at the design stage. Additionally, this study provides valuable guidance for minimizing environmental impacts during the design phase, enabling informed investment decisions before construction. Ultimately, it plays a crucial role in establishing a circular bioeconomy within the dairy industry by effectively utilizing the side streams to produce sustainable biobased chemicals, specifically LA.