ABSTRACT
Introduction: This study assesses the environmental impacts of mannosylerythritol lipids (MELs) production for process optimization using life cycle assessment (LCA). MELs are glycolipid-type microbial biosurfactants with many possible applications based on their surface-active properties. They are generally produced by fungi from the family of Ustilaginaceae via fermentation in aerated bioreactors. The aim of our work is to accompany the development of biotechnological products at an early stage to enable environmentally sustainable process optimization. Methods: This is done by identifying hotspots and potentials for improvement based on a reliable quantification of the environmental impacts. The production processes of MELs are evaluated in a cradle-to-gate approach using the Environmental Footprint (EF) 3.1 impact assessment method. The LCA model is based on upscaled experimental data for the fermentation and purification, assuming the production at a 10 m³ scale. In the case analyzed, MELs are produced from rapeseed oil and glucose, and purified by separation, solvent extraction, and chromatography. Results: The results of the LCA show that the provision of substrates is a major source of environmental impacts and accounts for 20% of the impacts on Climate Change and more than 70% in the categories Acidification and Eutrophication. Moreover, 33% of the impacts on Climate Change is caused by the energy requirements for aeration of the bioreactor, while purification accounts for 42% of the impacts respectively. For the purification, solvents are identified as the main contributors in most impact categories. Discussion: The results illustrate the potentials for process optimization to reduce the environmental impacts of substrate requirements, enhanced bioreactor aeration, and efficient solvent use in downstream processing. By a scenario analysis, considering both experimental adaptations and prospective variations of the process, the laboratory development can be supported with further findings and hence efficiently optimized towards environmental sustainability. Moreover, the presentation of kinetic LCA results over the fermentation duration shows a novel way of calculating and visualizing results that corresponds to the way of thinking of process engineers using established environmental indicators and a detailed system analysis. Altogether, this LCA study supports and demonstrates the potential for further improvements towards more environmentally friendly produced surfactants.
ABSTRACT
Biosurfactants are considered as an environmentally friendly and sustainable alternative to conventional fossil-derived and chemically produced surfactants. Their production pathways, physicochemical properties, and applications are widely researched and discussed in literature. In this context, investigating the different impacts from the entire life cycle of biosurfactants is important to understand and mitigate potential environmental hotspots. Life Cycle Assessment (LCA) is an internationally accepted and standardized methodology to analyze the environmental impacts of products from a holistic view. Therefore, this study provides a detailed overview of existing LCA studies of biosurfactants by means of a systematic literature research. The focus specifically lies on articles that investigated microbial biosurfactants. However, the systematic approach used ensured a broader overview related to bio-based surfactants as well. Furthermore, two related topics, ecotoxicity and biodegradability of biosurfactants, were identified and discussed based on the search findings. After screening over 2,500 documents using Scopus and Google Scholar, six relevant LCA articles of biosurfactants could be identified. The identified articles are divided into LCA studies of alkyl polyglycosides, chemically produced bio-based surfactants, and LCA studies of microbial biosurfactants, their content analyzed and discussed in context. In conclusion, the number of available LCA studies is very limited and their results are often not comparable. To the best of the authors' knowledge, this review is the first of its kind to provide a detailed overview of LCA studies of biosurfactants. Consequently, the need for implementing more LCA studies becomes clear.
