Estimating dynamic climate change effects of material use in buildings—Timing, uncertainty, and emission sources

Eirik Resch,Inger Andresen,Francesco Cherubini,Helge Brattebø

doi:10.1016/j.buildenv.2020.107399

Abstract

Material use in buildings affects the climate over centuries, however, temporal aspects are often ignored in Life Cycle Assessment (LCA). Results too often promise uncontested precision of impacts occurring far into the future. Additionally, the validity of building LCAs is being questioned over inadequate scope and inventory.A dynamic LCA method for material use in buildings that addresses those concerns is presented, along with a case study of 20 buildings. In particular, a novel solution to account for delayed emissions is presented, along with future technological improvements. Climate change effects of material use in construction, operation, and end-of-life phases are estimated, from production, transport, construction-waste incineration, biogenic carbon-sequestration, and cement carbonation. Building subpart metrics reveal drivers of impacts and are used for generating statistical emission profiles.Application on a bottom-up harmonized dataset produces statistical results for building types (typology, timber/concrete) and building subparts (building elements, material categories). Global warming policy targets requires that the building industry focuses on interventions with short-term effects, such as low-impact materials in the construction phase and reduced construction waste.Uncertainty is estimated, and parameter influence assessed with global sensitivity analysis. Time horizon (TH), building lifetime, and construction waste parameters are found most sensitive. The method reduces uncertainty of postulated future impacts; an important step in the direction of policy-relevant modeling. We recommend that building LCA modeling practice adopts the presented methodological concepts to gain trust and policy-relevance.

Highlights

Buildings are a large global source of anthropogenic greenhouse gas (GHG) emissions, which can be estimated by Life Cycle Assessment (LCA) methods
To address the limitations discussed above, we present a novel method for estimating the lifecycle impacts on climate change imposed by material use in buildings over clearly specified time horizon (TH)
Results for the other buildings in the dataset can be found in E.4.2, many of which have much lower future impacts

Summary

Introduction

Buildings are a large global source of anthropogenic greenhouse gas (GHG) emissions, which can be estimated by Life Cycle Assessment (LCA) methods. With growing focus on material embodied emissions in buildings, GHG emissions are usually quantified in kgCO2e per unit of material consumed or per m2 of floor area, according to the 100-year Global Warming Potential (GWP100) indicator and with data from Environmental Product Declarations (EPDs) from given manufacturers. The information from EPDs, together with material quantities and other data specific to the building form the basis for modeling its emission profile throughout its postulated lifetime. The validity of building LCAs has been questioned due to varying system boundaries and assumptions, lack of completeness, transparency in methodological choices, and reproducibility [1,2,3], and for ignoring time-dependent effects [4,5,6,7]. There are large uncertainties that are often not quantified and communicated [8]

Methods

Results

Discussion

Conclusion