Environmental sustainability of digestate-derived Rhamnolipids: Life cycle assessment approach

Rhamnolipids (RL) are promising microbial biosurfactants that offer the potential for environmental sustainability. This study conducted a Life Cycle Assessment (LCA) under two scenarios to evaluate RL production. The first scenario aimed to identify the optimal feedstock for RL production. Food waste digestate emerged as the most effective, supporting the highest biomass growth and RL concentration. Using the production of 1 g/L RLs as the functional unit, this production resulted in a cumulative energy demand (CED) of 176.06 MJ and a global warming potential (GWP) of 16.85 kg CO₂ eq when using digestate. When using a synthetic medium, these values were 140.88 MJ and 13.48 kg CO₂ eq, respectively. In the second scenario, the main contributors to the environmental impacts of fed-batch fermentation with digestate were examined. High energy consumption during the fermentation process was identified as a significant factor. Here, the production of 1 g/L RLs using a fed-batch fermenter with food waste digestate resulted in a CED of 539.2 MJ and a GWP of 51.62 kg CO₂ eq. It mainly resulted from the additional culturing step needed to acclimatize the RL producer strain on digestate before using it for fermentation in the bioreactor. This study provides important insights for improving the environmental sustainability of RL production through feedstock selection and process optimization. © 2025 Published by Elsevier Ltd.