A methodology to assess circular economy strategies for sustainable manufacturing using process eco-efficiency

A growing number of companies engage in sustainability, with early adopters already realizing financial and environmental benefits. However, the current linear production model followed by most manufacturers is widely recognized as not being sustainable. The circular economy model can be an eco-friendly alternative to production and consumption, ensuring a smooth transition to sustainable practices. In this study, the impact of various sustainable practices in manufacturing is reviewed as well as the impact of life cycle assessment in the quantification of the impact of the sustainable practices. However, a simple and fast methodology for manufacturers to get a first indication about the potential improvements in their production lines and required changes for adopting circular economy practices is missing from the literature. The main objective of this study is to provide a quantified methodology that facilitates decision-making at a manufacturing process and system level regarding the adoption of more sustainable strategies. An eco-efficiency indicator is proposed targeting the reduction of energy consumption and manufacturing waste caused by production operations, on top of the life cycle assessment and cost analysis of a process. The indicator combines a process's environmental performance, whose calculation is performed using life cycle assessment studies, and the process's value performance, whose calculation is derived from a combination of a life cycle costing analysis with the process and product-related metrics encapsulated under the umbrella of the overall equipment effectiveness, and of a cost of implementation metrics signifying the required cost for replacing existing equipment to adopt a circular economy strategy. Additionally, the indicator is not constrained by any geographical coverage and applies to any manufacturing use case as long as the life cycle assessment model is constructed using the ISO 14044:2006 standard. The proposed approach is examined in two industrial use cases, in which the proposed indicator is evaluated against three potential circular economy strategies for improved sustainability, the use of renewable energy sources, and material reuse.