Evaluating the Life Cycle Environmental Benefits and Trade-Offs of Water Reuse Systems for Net-Zero Buildings

Abstract

Aging water infrastructure and increased water scarcity have resulted in higher interest in water reuse and decentralization. Rating systems for high-performance buildings implicitly promote the use of building-scale, decentralized water supply and treatment technologies. It is important to recognize the potential benefits and trade-offs of decentralized and centralized water systems in the context of high-performance buildings. For this reason and to fill a gap in the current literature, we completed a life cycle assessment (LCA) of the decentralized water system of a high-performance, net-zero energy, net-zero water building (NZB) that received multiple green building certifications and compared the results with two modeled buildings (conventional and water efficient) using centralized water systems. We investigated the NZB's impacts over varying lifetimes, conducted a break-even analysis, and included Monte Carlo uncertainty analysis. The results show that, although the NZB performs better in most categories than the conventional building, the water efficient building generally outperforms the NZB. The lifetime of the NZB, septic tank aeration, and use of solar energy have been found to be important factors in the NZB's impacts. While these findings are specific to the case study building, location, and treatment technologies, the framework for comparison of water and wastewater impacts of various buildings can be applied during building design to aid decision making. As we design and operate high-performance buildings, the potential trade-offs of advanced decentralized water treatment systems should be considered.

Spatial optimization for decentralized non-potable water reuse

“…The in-building piping is calculated based on the area of the building and the number of floors. The average piping length per building area was approximated based on measurements of an existing typical building with water reuse infrastructure [27]. The piping costs are calculated as directly related to the piping length and diameter (SI-section 3) for economic cost [28], energy intensity and GHG emissions [29], and are reported in table S-1 in the supplementary information (SI) available at stacks.iop.org/ERL/13/064001/mmedia.…”

Whole Building Life Cycle Assessment of a Living Building

“…Lastly, a comparable study of the water system of another living building in Pittsburgh found that a standard building modeled with low-flow water fixtures had the potential to have lower life cycle impacts than a building with a complete wastewater treatment system on-site (Hasik et al, 2017).…”

“…An LCA was performed on the water system of another living building in Pittsburgh, the Center for Sustainable Landscapes (CSL) located at Phipps Conservatory and Botanical Garden (Hasik et al, 2017). The CSL's main purpose is to provide office space for employees of Phipps; it therefore has less foot traffic and fewer visitors in general than the FEC.…”

“…Then, a comparison between the water systems of the FEC and another living building in Pittsburgh, the Center for Sustainable Landscapes (CSL) is presented. Because a comprehensive LCA of the CSL's water system was previously performed, values from that assessment were adjusted when applicable to match the subsystems with the FEC's water system (Hasik et al, 2017).…”

“…Additionally, the energy demand for the CSL is in fact higher than that of the FEC due to the aeration but powering this system with slightly more renewable electricity has large payoff when it comes to overall life cycle emissions. Materials, emissions, energy, and water treatment included over 100 years per TRACI impact category (Hasik et al, 2017).…”