Hybridised sustainability metrics for use in life cycle assessment of bio-based products: resource efficiency and circularity

The development, implementation and social acceptance of resource efficient, circular, bio-based economies require critical understanding of the whole supply chain from feedstock to end-use. Trust, transparency and traceability will be paramount. Though life cycle assessment (LCA) is a universally chosen approach to fulfil this purpose, the nature of data required and the depth of analysis lead to complex interpretations of the findings. Herein, a new set of hybridised, first-line sustainability indicators, drawn from the principles of green chemistry and resource (material and energy) circularity, are reported. These flexible, potentially stand-alone metrics are demonstrated via application to an exemplary comparative LCA, incorporating the hybridised indicators including hazardous chemical use, waste generated, resource circularity and energy efficiency, from the gate-to-gate stages for the bio-based case studies and their petro-derived commercial counterparts. These metrics were observed to quantify critical new information relevant to our transition to a circular economy, bridging significant gaps in contemporary environmental impact assessment methodologies. Appropriate additional evaluations that examine the performance of metrics, when the embedded resource efficiency and circularity strategies are omitted, have also been undertaken and reported. The data drawn from employing these methods are crucial to inform and encourage operational optimisation, transparency in sustainability reporting and practices to a significant number of value-chain actors including manufacturers, policy makers and consumers.