An integrated framework for assessing the sustainability of components that make up the built environment

The built environment plays an important aspect of society. Not only is the built environment a physical entity, it is a complex socio-ecological system from which sociocultural activities and interaction with the physical infrastructure and with the natural environment arise. The consumption of materials and energy to maintain these infrastructures consequently result in wastes, emissions, and wasted energy that are rejected back into the environment at varying degrees. This research focused on assessing the sustainability of the built environment - specifically the following infrastructures that are part of the built environment: wastewater treatment systems, concrete pavements used for roads, and commercial and residential buildings. The overall goals included: (1) identifying, developing, and applying appropriate assessment tools for measuring sustainability of specific components that make up the built environment and (2) quantifying and comparing the environmental, economic and social aspects of different technologies and materials that make up the built environment. Three different wastewater technologies (mechanical, lagoon and terrestrial) were evaluated for their economic, environmental and societal sustainability using a set of indicators. Results indicate that terrestrial systems posed the least overall impacts compared to mechanical and lagoon systems. Operation and maintenance costs (labor, energy, and purchase of chemicals and replacement equipment) for mechanical treatment was approximately 4–5.5 times more than a lagoon system and 4–6.5 times more than a land treatment system. Energy use during the maintenance of a 5 million gallon per day (MGD) treatment plant indicate that mechanical systems cost 3 times more to maintain than lagoons systems, and 16 times more than a terrestrial system of similar capacity. An integrated assessment of the sustainability of green and built-up roof using life cycle assessment (LCA) approach and life cycle cost analysis (LCCA) indicate that green roofs are an environmental and economic viable option when costs, energy and emissions savings are considered. Energy savings of 43% are observed when using a green roof. Reductions in costs and conventional air pollutants (carbon monoxide, nitrogen oxides, sulfur oxides) and greenhouse gas (such as carbon dioxide, methane) were also observed in this study. Results from LCCA indicate that green roof costs almost 50% less to maintain then an average built-up roof over a 45-year building life. An economic input-output life cycle assessment (EIO-LCA) and an LCCA were used to compare the environmental and economic impact of Continuously Reinforced Concrete Pavement (CRCP) and Jointed Plane Concrete Pavement (JPCP). EIO-LCA results indicate that that JPCP pavement had 33-62% less emissions (carbon monoxide, nitrogen oxides, sulfur oxides, greenhouse gas) than CRCP pavements, when only steel was considered. When cement was considered, the JPCP had almost 40% more emissions then CRCP for all mix types studied. Results from the life cycle cost analysis indicate that CRCP pavements had about 46% more costs than JPCP over the entire life cycle phases studied. Maintenance cost analysis indicate that CRCP pavement cost 80% less to maintain then JPCP over the studied period of 35 years.