Biologicalisation of surface structuring: Comparative environmental assessment of microbial biomachining vs. chemical etching

In 2015, the United Nations adopted the 2030 Agenda for Sustainable Development in response to growing global concern about climate change, resource scarcity and environmental impacts on ecosystems. This agenda also places high demands on industrial manufacturing systems to promote sustainability. Biologicalisation of manufacturing processes can be a promising approach to contribute to the sustainability goals in industrial production systems. In recent years, biomachining has emerged as a field of research in biologicalisation with potential advantages compared to conventional surface treatment methods of metals, such as chemical etching. Surface structuring of metals plays a crucial role in various industrial applications, such as pre-coating preparation, hierarchical structuring, superhydrophobic surfaces and geometries. To assess the environmental impacts of biomachining, this paper focuses on environmental impacts of utilizing the bacterium Acidithiobacillus ferrooxidans compared to a conventional chemical etching process with cupric chloride solution for surface structuring of a metal specimen. The study examines the environmental impact of both processes, considering all relevant material and energy flows from cradle to gate for multiple environmental impact categories. In doing so, the environmental impacts of each process can be comprehensively evaluated and compared, and hotspots for future improvement of the biomachining process can be identified. On current lab-scale, the results indicate higher impacts for the biomachining process in most categories compared to the chemical etching process, mainly due to the energy demand for pre-cultivation and preparation of the biomachining solution.