Rainwater harvesting through roofs and stormwater harvesting through pervious pavements: A Life Cycle Assessment and decision-making comparison

Abstract

Water consumption and the building sector are among the top contributors to environmental impacts worldwide. Also, sustainable practices have been constantly encouraged in both sectors to mitigate water scarcity and provide resilience to cities. Thus, studies that provide an environmental assessment and discuss the decision-making process are essential for enabling the augmentation of sustainable practices. This research aims to contribute to the discussion on sustainability by conducting a Life Cycle Assessment (LCA) of Sustainable Urban Drainage Systems (SUDS) examples. LCA is the main methodology applied to perform environmental comparisons. First, a thorough inventory was obtained from previous works with different alternatives for water management within a university building, including drainage, paving and water supply functions. The inventory contemplates alternatives using rainwater and stormwater harvesting for non-potable water supply, including pervious pavements. Such alternatives were compared with Brazil's usual water supply systems, aiming at diminishing the total environmental burden. The methodology aspects of LCA were also regarded, such as an uncertainty assessment and a quality matrix of the processes used. Midpoint and endpoint categories were also regarded with their decision-making and uncertainty analysis. The main result is the understanding of the trade-offs between the proposed systems, with a significant reduction in water stress obtained in the alternative scenarios. However, such a decrease is accompanied by a slight increase in some impact categories. Rainwater harvesting through roofs is the most environmentally friendly alternative, although the Cultural Theory parameter definition impacts on the sustainability ranking. Alternative sustainable systems for water management still need validation in terms of LCA, while decision-making for sustainable and resilient cities also requires a robust scientific basis. Thus, in conclusion, alternative systems such as SUDS were obtained to be more sustainable than conventional paving, drainage and water supply in the case study, and the understanding of different benefits found in the LCA is important to the decision-making process.