How "Green" is Your Functional Material? Assessing Environmental Impacts of Multi-Step Synthetic Protocols in...

Environmental awareness is increasing worldwide, driven by alarming developments such as the climate change. Life cycle assessment (LCA) provides a standardized framework to evaluate environmental impacts, for example in the material sciences. While LCAs are widely used for mature technologies, application in early-stage research remains limited despite its high potential for sustainable improvements. This article introduces a broadly applicable formalism referred to as Environmental Synthesis Radar (ESR) to systematically evaluate the environmental impacts of multi-step chemical synthesis protocols. ESR goes beyond the typical consideration of only one particular environmental aspect (e.g. "global warming"), but rather considers 18 midpoint impact categories (MICs), and thus yields a much more holistic and conclusive view. Importantly, the ESR formalism can be applied independently of the field of application of the material of interest, the material specifics, and the maturity of the technology. Exemplarily, we apply ESR to two cathode material classes for use in secondary batteries: an organic material based on tris-(p-methoxy)-phenylamines (TPA) and an inorganic reference based on lithiated nickel-manganese-cobalt oxide (NMC). We obtain three important environmental metrics: (i) the per capita annual environmental output V_total, a single number for comparison of different materials and contextualized interpretation; (ii) the environmental fingerprint V_EF for identification of the most impactful MICs, and (iii) the process radar V_PR, which allows identification of environmentally critical synthesis steps and substances. ESR indicates that the impact of synthesizing 1 kg of the above materials is a factor of 3 (TPA) or 18 (NMC) below the global annual environmental emissions per capita, indicating that both are environmentally quite harmful. The laboratory synthesis of TPA is about one order of magnitude more harmful than the industrial production of NMC. Overall, ESR provides an easily accessible and very versatile tool for researchers-in academy as well as in industry-to evaluate and improve environmental performance of a material synthesis/production at an early stage when there is still lots of leverage. Importantly, it takes into account the holistic view of 18 MICs.