The solution, according to a group of researchers in Finland: develop carbon footprint standards for plants, soils, and mulches similar to those that already exist for building materials.
“Landscape designers will need to know how much carbon typical plants and growing media can sequester.
Based on this analysis, it’s clear that standard methods for assessing the carbon footprint of building materials will need to be tweaked when applied to components of green infrastructure, the researchers report in the International Journal of Life Cycle Assessment.
So the amount of carbon stored when, for example, young shrubs are planted in a park may not correspond to the amount stored years later after they’ve grown to maturity.
On the plus side, there are already widely used methods for modeling the carbon stock of trees and carbon storage in urban forests.
One source of complexity is that neither soils nor mulches have a clearly defined “end of life” stage: soil might be removed from a site and deposited elsewhere, but it’s still soil; mulch decomposes over time, yet there’s no clear demarcation of when it ceases to be mulch and becomes something else.
But one step at a time, says Kuittinen: “Next steps in translating our findings into EPDs will be compilation of data on the carbon uptake potential of bushes.