Cost-Benefit Analysis and Life Cycle-Assessment of Rainwater Harvesting in a Commercial Building

Abstract

This study examines the economic viability and environmental sustainability of implementing a rainwater harvesting (RWH) system in a six-story commercial office building through the integration of Cost–Benefit Analysis (CBA) and Life Cycle Assessment (LCA). Rapid urbanization, increasing water demand, and rising utility costs have intensified the need for alternative water management strategies in commercial developments. The proposed RWH system captures rooftop runoff, treats it through filtration units, and reuses the collected water for non-potable applications such as toilet flushing and landscape irrigation. The Cost–Benefit Analysis evaluates capital, operational, maintenance, and end-of-life costs against long-term financial benefits, including reduced municipal water consumption, lower wastewater fees, and resilience against future water tariff increases over a 20-year project life. Meanwhile, the Life Cycle Assessment assesses environmental impacts across manufacturing, installation, operation, and disposal phases. Results indicate that although the system entails significant upfront investment, the long-term economic savings outweigh total costs, yielding a favorable benefit–cost ratio. Environmental analysis further demonstrates net positive outcomes through reduced potable water use, lower energy consumption for water treatment, and decreased wastewater generation. Overall, the findings support rainwater harvesting as a practical, cost-effective, and environmentally responsible solution for commercial office buildings, contributing to sustainable urban water management and long-term operational efficiency.