Hybrid life cycle assessment at the neighbourhood scale: The case of Ydalir, Norway

Abstract

The focus of this study is Ydalir, a neighbourhood in Norway currently in the early planning stages. Ydalir aims to produce its energy locally based on renewable sources, has passive house standards or higher for all its buildings, uses timber or other materials with low embodied greenhouse gas emissions (EGHGE) as its main building materials and prioritises low emissions solutions for the mobility of its inhabitants. Because of those characteristics, the EGHGE related to the operational phases at Ydalir will be low and the relative importance of the EGHGE related to the materials will increase. The EGHE at Ydalir should thus be quantified in a comprehensive manner.

Hybrid life cycle assessment (hLCA), which combines process-based life cycle assessment (pLCA) with economic input-output (IO) data is well-suited for this task because a better system boundary completeness is achieved while maximizing the use of typically more reliable process data.

Regionalized (Norway) hybrid EGHGE coefficients are compiled for all the main construction materials. The proportion of the IO data (10–78%, average of 34%, and median of 24%) demonstrates the signification truncation associated with traditional pLCA.

The EGHGE related to the construction materials, the transport needed along the value chains and to the construction site, and the use of fossil fuels along the value chains (in particular coal) is significant and must be addressed as part of a holistic approach to reducing the EGHGE of our buildings and neighbourhoods, in- and out-land.