Ecosystem Science-Based Absolute Environmental Sustainability Assessment of Chemical Products with and without Climate Justice

To halt climate change and reverse nature loss, stakeholders are increasingly prioritizing a transition to a "net-zero" and "nature-positive" future. Guiding the chemical industry toward such a future is urgently needed due to the importance of chemical products in fulfilling essential human needs while also posing significant environmental risks. Absolute environmental sustainability (AES) assessment has recently emerged as a tool for evaluating the sustainability level of products, processes, techniques, etc. AES assessment relates a system's impact with its allowable biophysical threshold, which provides more meaningful results compared with relative sustainability assessment such as life cycle assessment (LCA). However, current AES assessment methods are mostly subjective and aggregated while failing to use readily available scientific knowledge. In this work, we utilize a multiscale, ecosystem science-based AES assessment method for products that utilize regional scientific data and biophysical models rather than subjective direct downscaling. We conduct AES assessment of four major chemicals: ammonia, methanol, ethylene, and benzene, in nine countries. Notably, all four chemicals overshoot their ecological thresholds in these countries, except Russia, a trend not adequately captured by the current approach of global-scale assessments. This scientific approach also encourages actions, such as ecosystem restoration and chemical process optimization. Furthermore, we emphasize the crucial importance of incorporating historical cumulative emissions into AES assessments from the perspective of climate justice. This marks the first instance of integrated climate justice into AES.