Life cycle assessment of surfactants: The case of an alkyl polyglucoside used as a self-emulsifier in cosmetics

Abstract

Purpose: Cetearyl glucoside and cetearyl alcohol are an alkyl polyglucoside composition (APG) widely used in personal care as an efficient and versatile self-emulsifier. This ingredient is considered as green thanks to its vegetable origin and to its manufacturing process complying with the 12 rules of Green Chemistry. Beyond these general criteria, the rising environmental concern among consumers encourages manufacturers to provide quantifiable measures highlighting the real impacts of a product on the environment. In order to respond to this need, the aim of this work was to study, from an environmental point of view, the contribution of the use of APG in a cosmetic cream (raw materials, glucosylation process, formulation process, chemical inputs, energy, transport, waste management, end use, and recycling) and to assess several potential improvements to decrease its global impacts. Materials and methods: The methodology used was the life cycle assessment (LCA) according to the ISO 14-040 standard. Two approaches were chosen: (a) from the cultivation of vegetable raw materials to the final use by consumers and recycling (from cradle to grave) and (b) from the cultivation of vegetable raw materials to the production of APG (from cradle to gate). The two corresponding functional units were defined as follows: (a) the preparation of a cosmetic oil in water emulsion having suitable stability and allowing the face hydration of a consumer during 1 year and (b) the preparation of 1 t of packaged APG in a plant located in the South of France. To comply with these two functional units, the life cycle was divided into 4 phases (gate to gate): the agricultural and transformation phase A, the chemical process phase B, the formulation process phase C and finally the end use phase D. The life cycle inventory data collected were based either on bibliographical sources or on direct industrial data. Seven impact categories were selected for their relevance (ozone depletion, global warming, mineral resources, petrochemical resources, eco-toxicity, acidification/eutrophication, and water consumption). For each significant environmental impact, sensitivity assessments were carried out to identify potential improvements regarding the two functional units. Results and discussion: The results show that the formulation process phase C and the end use phase D are the main key issues of the cosmetic cream life cycle. Their respective environmental contributions are between 15 and 51% and between 30 and 77% depending on the impact category. Regarding the formulation step, the two most contributing parameters are the emulsion oil and the cream packaging. The impacts of oil are directly linked to the quantity involved (20% in the cream) and also to the cultivation conditions of the plant from which the oil is extracted. A sensitivity study on the nature of the packaging highlights that glass is much better than PET. As far as the end use of the cream is concerned, the main impacting parameter is the purchasing by the consumer (between 33 and 77%). It was clearly proved that APG has relatively low impacts when it is formulated at 5% in a cosmetic cream (between 4 and 24%). Despite this low contribution, the environmental profile of APG was examined and indicated the high impacts of the cetearyl alcohol (more than 80% by weight in APG). For instance, the carbon footprint of APG directly depends on the cultivation mode of the palm trees and, according to the land use change, it can vary between 1.9 and 49.8 t CO2 eq. per t of APG. The impacts directly due to the glucosylation process are between 2 and 12%, mainly coming from the transport of raw materials and waste management. Conclusions: The present LCA gave a precise picture of the role that APG plays in the environmental profile of a cosmetic emulsion. The next step may be to compare its impacts with those of other surfactants that also respond to the first functional unit in order to functional unit in order to confirm the green status of this kind of biosurfactant. Finally, improvements in APG processing and use can also be brought about and all levels of the production chain are relevant: raw material suppliers (fatty alcohol quality and transport), APG manufacturers (utilities consumption follow-up, waste management and transport), finished cosmetic product formulators (packaging) and final consumers (transport mode).