Comparative Life-Cycle Assessment of Bottled vs. Tap Water Systems
This study uses life-cycle assessment (LCA) methodology to quantify life-cycle energy use, greenhouse gas emissions, solid waste generation and water use for delivering drinking water to consumer households in the United States. Three systems were considered in this analysis: 1) single-use disposable bottled water (500ml) sold in 24-packs, 2) Home and office delivery bottled water, 3) municipal tap water. For both the HOD and municipal tap systems, drinking water is served in a reusable drinking vessel (bottle or cup) that is periodically washed in a residential dishwasher. Variants of each system were constructed to represent a range of possible real-world scenarios using factors such as bottle type (virgin PET, rPET), water type (natural source, municipal source), distribution (regional, national, overseas), end-of-life treatment (landfill disposal, recycling), type of reusable drinking vessel (steel bottle, glass cup) and frequency of washing the reusable vessel.
With respect to life-cycle energy, solid waste, greenhouse gas emission and water use, the municipal tap systems outperform both HOD and single-use bottled systems. Single-use bottled systems consume 11-31 times more energy than tap systems. Production of plastic bottles is responsible for over 70% of the energy use of regional bottled systems, while with national and overseas distribution, transportation begins to dominate. Tap and HOD system energy use is dominated by residential washing of the reusable drinking vessel. Greenhouse gas emissions generally correlate with energy use. HOD systems consume 8-18% of energy relative to single-use systems, while municipal tap systems use 35-55% of HOD life-cycle energy. For solid waste, single-use systems perform the worst, followed by the HOD and municipal tap systems respectively. End-of-life treatment of bottles dictates single-use systems solid waste profile.
From an environmental perspective, municipal tap water is the preferred drinking water system.
Strategies to reduce the impact of bottled water may include bans at the organizational level (city governments, universities, and restaurants), education and outreach to encourage consumers to choose tap water and the expansion of state bottle bills to improve recovery of empty bottles. Results of this study can be used to inform consumers and legislators of the impacts of their choices with regard to drinking water.