General equations to estimate the CO2 production of (bio)catalytic reactions in early development stages

Global warming potential (GWP, kg CO2eq per kg product) is a core impact indicator when assessing the greenness of synthetic reactions in life cycle assessments (LCAs). GWP contributions arise from the production and transportation of chemicals, solvents, and catalysts to the chemical plant, from the reaction (upstream), from the purification steps (downstream), and from the energy invested in the process. For (bio)catalysis, water and spent organic solvents are the major waste contributors, from which CO2 is generated through their processing via wastewater treatment or incineration. Assessing GWP in organic synthesis appears wearisome, demanding time, resources and expertise. However, GWP estimations at early process stages would rapidly identify the hotspots to improve the environmental impact. This paper proposes equations that can be combined depending on the reaction, to estimate the GWP by using readily available process parameters (substrate loading, conversion, reaction media, temperature, time, and thermodynamic values). Once equations are chosen for each reaction (e.g. process conducted in water or in organic media, type of downstream, etc.), estimated GWP can be obtained. Scenarios can be simulated by changing parameters, to assist practitioners at process early stages to understand how (bio)catalytic reactions can be established in a greener way.