improvements on the MCI whilst y-axe represents improvements on human health,
ecosystems and resources damage scores.
Results reveal that the two types of tire end-of-life management analysed tend to
improve the level of circularity from the baseline scenario, as per the MCI, but it is
not fully conclusive on environmental damages. Re-grooving follows on a
decoupling pathway on all impact categories, whereas re-treading potentially shifts
burdens on human health and resources. This is due to the increased fuel consumption required to offset the rolling resistance.
It could be tempting to conclude that re-treading improvements on circularity
and ecosystem quality indicators are substantial enough to balance the small
increase of damages on human health and resources, but this typical conclusion
jeopardizes the preservation of natural capital itself—and consequently the contribution of circular strategies to a sustainable development. A more conservative
approach then would be to conclude that only re-grooving improve natural capital
preservation.
4 Discussion
Preceding results display areas of protection—as per ReCiPe—as the ultimate
expression of environmental reservoirs subsets. Two important discussions stem
from this observation. First, one could say that other trade-off on environmental
reservoirs can occur when downscaling to mid-point categories. We considered
reasonable to assume that mid-point categories can offset one another when contributing to the same damage category. Note that this works also for circularity
when resource preservation refers to different subsets of stock of resources yet, this
does not concern the MCI as it has no subcategories. The second logical issue is
about comparing resources at damage category level and the MCI. The preceding
illustration makes them appearing complementary as they derive from distinct
assessment methodology. However, as both refer to natural feedstock preservation,
they should follow the same trends, yet they do not.
The MCI methodology contains many limitations. For instance, system
boundaries definition is narrower than in LCA, which makes the MCI ineffective to
prevent from consequences of shifting resources consumption at macro scale as it
refers only to one specific resource at the foreground level. Moreover, it excludes
energy flows which entail neither consideration for the fuel consumption due to the
increased rolling resistance nor for end-of-life energy recovery routes. Whereas, the
LCA resource indicator refers to the marginal increase in costs for future extraction
due to the extraction of a resource over the life cycle of the assessed product, i.e. the
additional costs society has to pay as a result of an extraction [17], embodying
resource depletion issues, unlike the MCI.
Finally, as the CE is meant to contribute to a sustainable development, the other
sustainability dimensions are also relevant concerns. Not only social aspects are
here neglected, but excluding economic factors fails to account for the dreaded
40
G. Lonca et al.
ecosystems and resources damage scores.
Results reveal that the two types of tire end-of-life management analysed tend to
improve the level of circularity from the baseline scenario, as per the MCI, but it is
not fully conclusive on environmental damages. Re-grooving follows on a
decoupling pathway on all impact categories, whereas re-treading potentially shifts
burdens on human health and resources. This is due to the increased fuel consumption required to offset the rolling resistance.
It could be tempting to conclude that re-treading improvements on circularity
and ecosystem quality indicators are substantial enough to balance the small
increase of damages on human health and resources, but this typical conclusion
jeopardizes the preservation of natural capital itself—and consequently the contribution of circular strategies to a sustainable development. A more conservative
approach then would be to conclude that only re-grooving improve natural capital
preservation.
4 Discussion
Preceding results display areas of protection—as per ReCiPe—as the ultimate
expression of environmental reservoirs subsets. Two important discussions stem
from this observation. First, one could say that other trade-off on environmental
reservoirs can occur when downscaling to mid-point categories. We considered
reasonable to assume that mid-point categories can offset one another when contributing to the same damage category. Note that this works also for circularity
when resource preservation refers to different subsets of stock of resources yet, this
does not concern the MCI as it has no subcategories. The second logical issue is
about comparing resources at damage category level and the MCI. The preceding
illustration makes them appearing complementary as they derive from distinct
assessment methodology. However, as both refer to natural feedstock preservation,
they should follow the same trends, yet they do not.
The MCI methodology contains many limitations. For instance, system
boundaries definition is narrower than in LCA, which makes the MCI ineffective to
prevent from consequences of shifting resources consumption at macro scale as it
refers only to one specific resource at the foreground level. Moreover, it excludes
energy flows which entail neither consideration for the fuel consumption due to the
increased rolling resistance nor for end-of-life energy recovery routes. Whereas, the
LCA resource indicator refers to the marginal increase in costs for future extraction
due to the extraction of a resource over the life cycle of the assessed product, i.e. the
additional costs society has to pay as a result of an extraction [17], embodying
resource depletion issues, unlike the MCI.
Finally, as the CE is meant to contribute to a sustainable development, the other
sustainability dimensions are also relevant concerns. Not only social aspects are
here neglected, but excluding economic factors fails to account for the dreaded
40
G. Lonca et al.