Sand surrounds us–and while it may seem in infinite supply, it is not. Currently, sand is being used up much faster than it is being replenished. Sand and gravel, collectively known as aggregate, are the most widely extracted solid materials on Earth. A recent report by the United Nations Environment Programme recognizes sand as a strategic resource–and one with looming challenges.
The second-most-used substance on Earth is concrete; the first is water. Enormous volumes of cement and concrete are produced each year, and amounts are rising significantly with population growth and emerging economies. Concrete is a major greenhouse gas contributor to climate change, so reductions in this footprint are critically needed.