Pablo Domı́nguez de Marı́a
In a previous work, equations were reported to estimate global warming potential (GWP, kg CO 2 kg product −1 ) of (bio)catalytic reactions, using substrate loadings and conversions. The approach is useful for reactions with similar mass‐to‐mass proportion (substrate to product). For processes with mass‐to‐mass change, or for fermentations, where the relationship substrate to product is elusive, GWP equations using product titers are more straightforward. This article introduces such product‐titers‐based GWP equations estimating the CO 2 released from energy (up‐ and downstream), as well as from the waste treatment, namely wastewater and solvents. Equations are applied to discuss whether aqueous (bio)transformations with product titers of 1 g L −1 and extractive downstream are sustainable. When effluents are not recycled, >6000 kg CO 2 kg product −1 is generated, because large aqueous media (1000 L) and solvents (1000–3000 L) are needed for one product kilogram. Even when solvent and water effluents are almost completely recycled (95%), >100 kg CO 2 kg product −1 is still generated. For better environmental figures, process intensification with less diluted systems is mandatory. Setting product titers of ≈20 g L −1 with large recycling loops (95%) and mild wastewater treatment decrease the overall GWP to ≈10 kg CO 2 kg product −1 . GWP estimations at early development are useful in improving processes with low TRLs.