A GIS Methodology for Estimating the Carbon Footprint in Municipal Water and Wastewater in Fairfax County, Virginia

Abstract

ABSTRACT The carbon footprint metric is a useful tool for predicting the impact of a building or process on the environment. Many industries are developing models that perform the life cycle assessment of the carbon footprint based on energy consumption. These models typically do not consider the embodied energy associated with the treatment and distribution of water to and from the facility. A tool was developed for use by Fairfax County, VA, planners that estimates the tons per year of carbon dioxide equivalent for commercial, industrial, and residential building water use. This estimate includes the embodied energy requirements needed to collect, treat, and distribute water and wastewater. This model can be used by planners to evaluate the environmental impact of proposed and existing facilities. The estimation of energy consumption and subsequent carbon footprint calculation relies not only on the quantity of water distributed but also on the geography of the distribution and collection network. Distance from the plants and elevation were shown to play a significant role in the determination of the energy consumption.[1] A geographical information system (GIS) was developed (using ArcGIS Desktop Version 9.2) for Fairfax County that converts the annual water and wastewater needs for a facility into tons of CO2 per year. This tool answers critical questions related to the impact of demand-side sustainable water practices on the comprehensive carbon footprint. In April 2007, the American Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE) held a workshop in Washington, DC, on forecasting carbon emissions from buildings. An important result of this workshop was the identification of future research needs, which included “embodied energy and emissions associated with water use in the building.” This would be highly site-specific, depending on characteristics of the local water supply and treatment system. (ASHRAE Workshop Report, 2007.) This work begins to address the need identified by ASHRAE in investigating the carbon footprint of the embodied energy in municipal water and wastewater.