A Comparative Study of Rainwater Harvesting, Greywater Recycling, and Water-Efficient Landscaping in Buildings Within Lagos Mainland Local Government Area of Lagos State, Nigeria

This study compares the effectiveness of rainwater harvesting (RWH), greywater recycling (GWR), and water-efficient landscaping (WEL) in enhancing water efficiency in buildings across the Lagos Mainland Local Government Area, Nigeria. Using a qualitative approach, the research analysed 10 case studies (residential and commercial buildings) alongside a comparative review of global best practices. The literature review looks at water audits were conducted to assess water savings, cost benefits, and implementation challenges. Findings reveal that RWH yields the highest savings (30–40%) during peak rainy seasons, while GWR provides consistent reductions (20–30%) but requires higher maintenance. WEL reduces outdoor demand by 15–20%, though its impact is climate-dependent. A cost-benefit analysis reveals that RWH is the most economical option, with a payback period of 3–5 years, whereas GWR is more suitable for larger buildings, despite its higher initial costs. Key barriers include upfront expenses, lack of policy enforcement, and low public awareness. A comparative literature review highlights that Lagos lags behind cities like Cape Town and Singapore in adoptiondue to weak regulatory frameworks. Recommendations include government incentives, public-private partnerships, and pilot projects to scale adoption. The study concludes that an integrated approach combining RWH, GWR, and WEL offers the most sustainable solution for Lagos Mainland’s water challenges.