Carbon, Water and Energy Implications of Rainwater Harvesting in Educational Buildings

1. Carbon, Water and Energy Implications of Rainwater Harvesting in Educational Buildings Hannah West, Dr. Defne Apul Department of Civil Engineering, University of Toledo, Toledo, OH Four Possible Scenarios Abstract Results Potable water used for irrigation and flushing toilets. Rainwater used for irrigation, potable water used to flush toilets. Potable water used for irrigation, rainwater used to flush toilets. Rainwater used for irrigation and flushing toilets. Rainwater harvesting to supply non-potable water demands has become a viable option to eliminate water shortages in the future and reduce the burden on municipal water treatment facilities, but what if a large amount of additional materials that emit an excessive amount of CO2 during their manufacturing are needed to implement the system? It is possible that one’s efforts to improve the environment could actually harm it greater than if no sustainability effort was implemented. The goal of this study was to address these questions. A life cycle assessment approach was used to estimate the CO2 emissions and energy consumption associated with different rainwater management scenarios for the North Engineering (NE) building at the University of Toledo. The scenarios vary with respect to end use of the rainwater. The four scenarios were compared by calculating the amount of water sent to storm sewer, potable water required, energy usage, CO2 equivalence and cost. This study showed that if rainwater were used for both irrigation and flushing toilets at the NE building, the system would need to be implemented for a minimum of 16 years in order to be sustainable due to the CO2 emissions associated with the construction and operation of the system. It was also determined that this option would pay for itself in approximately 6 years when taking into account the decrease in water bills. System Boundary of the Sustainability Analysis Figure 4.Potable Water Savings Background Figure 2. System Boundary Parameters Used in the Calculations Figure 5. CO2 Tradeoff Table 1. Values for Water Treatment and Distribution Sahely, H.R, and Kennedy, C.A (2007). “Water Use Model for Quantifying Environmental and Economic Sustainability Indicators.” Journal of Water Resources Planning and Management. 133(6) (550-559). Figure 6. Cost Tradeoff Conclusion • If rainwater were used for both irrigation and flushing toilets at the North Engineering Building: • 205,357 liters of potable water would be saved per month (see figure 3). • The system would need to be implemented for a minimum of 16 years to overcome the CO2 emissions associated with its construction (see figure 4). • The system would pay for itself in approximately 6 years when taking into account the decrease in water bills. Figure 1. Entrance of NE A rainwater harvesting system was analyzed for the North Engineering building at UT. Potable water savings, energy consumption, CO2 emissions and costs were compared for the four scenarios which vary with respect to end use. Objective Figure 3. EIO-LCA Output, Energy Associated with Construction A hybrid life cycle assessment approach was used to estimate the energy and CO2 emissions. The values in table 1 were combined with values from EIO-LCA to determine the overall energy and CO2 emissions associated with the implementation of the four scenarios. Acknowledgements • To determine the optimum scenario to be implemented for the North Engineering Building in terms of potable water savings, energy usage, CO2 emissions and cost. This work was supported in part by a grant through the UT Office of Undergraduate Research and the Lake Erie Protection Fund (LEPF).