Audit of the environmental footprint caused by the production of a mechanical watch equipped with a sapphire glass
Context and challenges
This project is a case study of a hypothetical watch piece, aiming to represent a typical Swiss watch.
The analysis was performed with the help of the Granta Edupack software, courteously provided by Ansys and in collaboration with a class of engineering students in Industrial Design Engineering led by David Weber, scientific assistant in the watchmaking research department of HE-Arc.
Understanding how and where the watch industry uses energy is essential to identify areas that contribute most to the emission and find innovative solutions to reduce their footprint.
As the main goal of this study is to evaluate the impact of each component of the watch in the global energy consumption, the estimation made in this study is a partial eco-audit. Contrary to a global study, only embodied material energy and manufacturing processes were considered. Transportation between each step, use, maintenance and recycling were not considered because we estimate that their analysis would have relied upon too many hypotheses.
We calculated the total required energy and emitted CO2 by adding values contributed by:
– initial material production, defined as “Embodied energy & CO2 footprint of primary production” in Granta Edupack
– manufacturing of each component or “Material processing energy & CO2” in the Granta Edupack database.
We calculated that the total energy required for one watch to be 22.20± 1.03 MJ. This is equivalent to heating 66 liters of water from 20°C to 100 °C. The total CO2 emitted is 1.52±0.08 kg, that corresponds to 12.9 km driven by a modern car emitting 118 grams of CO2 per kilometer.
The evaluation of micro-machining and special processes as used in the watchmaking industry may differ from the mean values used in the Granta database for standard mechanical machining. Therefore, the proportion between parts footprints is more pertinent than the absolute amount of energy and CO2 calculated in this study.
Our study revealed that:
- for the entire watch, except the sapphire cover, the embodied energy is much more important than the manufacturing one. The choice of material and its origin therefore is the most critical parameter.
- the manufacturing energy for the sapphire stands out as one the most consuming in energy for its weight, accounting for 61% of total manufacturing energy requirements.
This last conclusion indicates the priority that eco-friendly watch brands should address.