PNNL

Abstract

When performing Whole-Building Life Cycle Assessments (WBLCA), emission calculations from the building’s operation over the entire building lifespan are typically based on today’s energy grid mixes. This method fails to consider the potential for changes in the clean energy proportion within the grid mix and can give inaccurate weight to the operational component of a building’s emissions, providing an inaccurate ratio of embodied vs operational environmental impacts. While prediction tools cannot guarantee accuracy, they can provide an understanding of the potential magnitude of impact associated with factoring in dynamic grid emissions instead of static emissions. To predict the clean energy ratio within future grid mixes, we collected data from several existing peer reviewed grid models. We analyzed the data to understand what future grid mixes might look like. The summary of existing models indicated that renewable energy sources will likely continue to increase over time, although the rate of growth varies by model. To understand the impact of the future grid mix within a WBLCA context, we analyzed a simple residential building. The results indicate that future grid mixes will reduce the carbon emissions over the life cycle of most buildings. The baseline home LCA considered in this study shows a possible reduction of approximately half of the total kgCO2eq between 2025 and 2100. The study confirms that using current grid mixes for LCA studies provides a conservative approach to modeling operational carbon.