Environmental Impacts Arising from the Production of Microbial Biosurfactants Rhamnolipid and Mannosylerythritol Lipid
Main Presenter: Andreas Schonhoff
Co-Authors: Andrea Schreiber Petra Zapp
Increased use of assessment methods, classifying the environmental impacts of novel products, already in their development phase, reflects today’s growing interest in sustainable products. Especially bio-based development of widespread products like surfactants in the context of an intended transformation into a future bioeconomy requires robust assessments of such aspects. Based on substrates from sugar industry (molasses, sugar beet pulp) four different processing routes for the two biosurfactants rhamnolipid (RL) and mannosylerythritol lipid (MEL) by strain engineered microorganism Pseudomonas putida (for RL) and Ustilago maydis (for MEL) were developed in the project Bio².
Regarding the environmental evaluation of products and optimization potentials of underlying process chains, a Life Cycle Assessment (LCA) in line with ISO 14040/14044 was carried out. To compare the developed biosurfactants with selected currently established oleo-/petrochemical surfactants the specific cleaning performance (SCP) was taken to define a functional unit based on the critical micelle concentration (CMC). The assessment comprises 16 indicators of the Environmental Footprint methodology EF 3.0.
The cradle-to-gate systems for biosurfactant production were modelled in GaBi LCA software from substrate supply up to the products RL and MEL. Industrial scale of 15,000 kg/a production was considered, scaled up from information obtained by lab and pilot scale (112.5 L fermentation operation volume) experiments. Depending on targeted products as well as used substrates, process modules of the foreground processes (e.g., fermentation or extraction stage), required infrastructure (e.g., pumps or storage tanks), and background processes (e.g., electricity or chemicals production) were included. The impact assessment results illustrate clear advantages of MEL production and the significant effects of operating materials (e.g., solvents). This was shown by the analysis of different processes and flows, where the influence of background processes became visible (e.g., precipitation agent production). Sensitivity analyses of specific parameters (e.g., yield of fermentation) have shown limits of parameter changes (e.g., environmental impact vs. feasible yields). The comparison with conventional surfactants’ production drew a variable picture for RL and MEL and provided an insight into the framework conditions of competitive biosurfactants. Furthermore, the comparison revealed further potential for improvement and led to new research issues for future studies.
The presented results provide indications for the developed process chains with regard to an environmental impact decrease. Furthermore, exemplary common problems from the field of emerging technology assessment in general and bio-based processes in particular are addressed.