  In upcoming years, the number of Internet-of-Things (IoT) devices is expected
to surge up to tens of billions of physical objects. However, while the IoT is
often presented as a promising solution to tackle environmental challenges, the
direct environmental impacts generated over the life cycle of the physical
devices are usually overlooked. It is implicitly assumed that their
environmental burden is negligible compared to the positive impacts they can
generate. In this paper, we present a parametric framework based on hardware
profiles to evaluate the cradle-to-gate carbon footprint of IoT edge devices.
We exploit our framework in three ways. First, we apply it on four use cases to
evaluate their respective production carbon footprint. Then, we show that the
heterogeneity inherent to IoT edge devices must be considered as the production
carbon footprint between simple and complex devices can vary by a factor of
more than 150x. Finally, we estimate the absolute carbon footprint induced by
the worldwide production of IoT edge devices through a macroscopic analysis
over a 10-year period. Results range from 22 to 562 MtCO2-eq/year in 2027
depending on the deployment scenarios. However, the truncation error
acknowledged for LCA bottom-up approaches usually lead to an undershoot of the
environmental impacts. We compared the results of our use cases with the few
reports available from Google and Apple, which suggest that our estimates could
be revised upwards by a factor around 2x to compensate for the truncation
error. Worst-case scenarios in 2027 would therefore reach more than 1000
MtCO2-eq/year. This truly stresses the necessity to consider environmental
constraints when designing and deploying IoT edge devices.
