Impacts of booming concrete production on water resources worldwide
By Sabbie A. Miller, Arpad Horvath, and Paulo J.M. Monteiro
The paper in Nature Sustainability is here: http://go.nature.com/2FdvI67
Concrete is the second most used material in the world next only to water. It is used in building homes, skyscrapers, bridges, roads, tunnels, and is a staple of most developed areas. Currently about 30 GT of concrete is used annually, about enough to cover the state of California with a 30 cm deep layer of concrete every year.
Concern about the sustainability of concrete has primarily focused on its greenhouse gas (GHG) emissions. Production and use of concrete accounts for almost 8-9% of total global anthropogenic GHG emissions. While reviewing emerging mitigation methods to reduce these GHG emissions for our recent article in Nature Materials , we realized that there had been scant attention to another environmental impact of concrete: the amount of water it uses.
In this paper we map and quantify water demand from the production of concrete and how that relates to the availability of water resources in countries around the world.
Using a database we had compiled on country and regional resource use, we quantified the demand for water at each phase of production of concrete. The database incorporates the demands different regions have for concrete by mechanical requirements, namely strength, the use of different constituents (cement, water, aggregate such as sand and gravel, and other materials) in different regions, and resource availability by region. For the assessment of water demand, we started with water used as a constituent. Water reacts with the cement to produce a rock-like product that holds concrete together. Then we extended the database to include water demand in material quarrying, energy demand for the refinement and manufacture of the constituents in concrete, as well as transportation requirements for these materials.
The results highlight that the high demand for concrete is impacting global water demand. While other activities, such as agriculture, demand far more water, concrete production alone is responsible for 9% of industrial water withdrawal (or 1.7% of total global water withdrawal). With projections for population growth, demand for water to produce concrete will continue to grow. Unless mitigation strategies are implemented this will create water stress in some geographic areas and exacerbate it in others. Over the next 35 years, the global water withdrawal for concrete production, if unchecked, will be equivalent to the total water withdrawal (agricultural, industrial, residential, and municipal) for the past 5-6 years in the United States. The findings of this study suggest that the GHG emissions from concrete production should not be our only consideration as we continue to advance the science behind making this ubiquitous material more sustainable.
 Monteiro, P.J.M., Miller, S.A. & Horvath, A. Towards Sustainable Concrete. Nature Materials, 16, 698-699, doi:10.1038/nmat4930 (2017).