Soil carbon sequestration in building life cycle assessment: Offsetting measure or site impact

Abstract

Abstract The environmental impacts of the built environment typically focus on the materials and operations within the building envelope. Little, if any, consideration is given to impacts that occur outside the building. This can be an appropriate simplification for urban settings where the building dominants the site. However, it would ignore impacts and benefits associated with site activities in more rural settings. The present study investigates soil carbon sequestration (SCS) principles to determine whether SCS can be considered an offsetting measure for buildings or should be considered within the site impacts for a project. Soil organic carbon (SOC) levels change overtime in response to external factors and interventions, however this response time is within the reference study period commonly used for building-scale life cycle assessments (LCAs). Therefore, it would be plausible to monitor changes in SOC throughout the lifespan for a project. Currently, there are some emerging methods but no consensus standards on accounting for SCS in building LCAs and current methodologies for quantifying SCS need further development to align with carbon offset principles. However, since soil is an intrinsic part of the landscape, it would be appropriate to incorporate SCS within the use phase impacts for a site. Expanding the system boundary to account for SCS should include accounting for the environmental impacts associated with landscaping, maintenance, and land management practices. Guidelines for calculating SCS and landscaping environmental impacts need to be developed to better reflect the complete environmental impact of the built environment.