Sand can be found everywhere there is land. For anyone who has walked on a beach or visited a desert, the supply of sand seems endless. Sand can also be found at the bottom of rivers, lakes and oceans. Sand comes from rocks eroded by weathering and mechanical abrasion and the sand we see has taken thousands or millions of years to form.
Sand is an important building material. For example, for each tonne of cement used six to ten tonnes of sand are needed. Demand for sand is expected to increase significantly to meet the demand for housing, infrastructure and growing cities in developing regions of Africa and Asia.
Not all sand is the same and differences depend, for example, on the source rock, the grain size and the organic content. Building grade sand must meet certain standards depending on what it will be used for. Sand from the desert is too smooth to use as a binding agent and sea sand contains too much salt. Most sand for construction is mined from rivers, lakes and the coast but the rate at which suitable sand is produced cannot meet the anticipated future demand. There is no infinite supply of sand.
Xiaoyang Zhong and his co-workers at Leiden University in The Netherlands have estimated that the demand for building sand could increase by about 45% from 3.2 billion tonnes a year in 2020 to 4.6 billion tonnes by 2060. They acknowledge that this is an underestimate because the study only looked at the amount of sand required for glass and buildings. The largest increase in building sand use is expected to be in Western and Eastern Africa (500% increase), followed by Southern Africa (419% increase), India (294% increase) and the rest of Asia (269% increase).
Sand extraction comes with environmental and social costs. Sand mining in rivers can affect the river ecosystem causing pollution, bank instability and increased flood frequency. Extraction can also reduce sediment delivery to coastal areas and river deltas which accelerates beach erosion and impacts biodiversity and communities dependent on these resources.
A United Nations Technical Report on Sand and Sustainability proposes a hierarchy of solutions. It starts with (1) reducing sand extraction, followed by (2) using recycled and alternative materials to replace natural sand and then (3) avoiding unnecessary consumption of natural sand.
Replacements for natural sand include reusing waste aggregates, recycling concrete and substituting sand and gravel in concrete production with waste products from other processes such as fly ash, waste foundry sand and stainless steel slag.
Sand extraction is an issue that has received relatively little attention in the past leading to significant social and environmental impacts in India, China and places in Africa and South America. Action is required to reduce sand use, avoid the secondary impacts of sand extraction and meet the needs of the next generation, especially in developing nations, for building materials.