ARE WE RUNNING OUT OF SAND?

The voracious industrial demand for sand has led to an improbable global shortage – and an environmental crisis

Why is there such demand for sand?

Much of the global economy depends on it. Sand is used to manufacture everything from glass and electronics to paint and tyres. It plays a crucial part in metal casting and water filtration; hydraulic fracking for oil and gas involves propping open rock fissures by injecting vast quantities of sand. But most of all, sand is used in construction. Aggregate – sand and gravel – is the main ingredient in concrete and asphalt; it is also used under foundations and in land reclamation. “Sand and gravel represent the highest volume of raw material used on Earth after water,” stated a United Nations Environment Programme report in 2014. The volumes involved are mindboggling, thanks primarily to Asia’s rapid urbanisation. Around 26 billion tonnes of aggregates were used for concrete in 2012: enough to build a wall 27 metres high by 27 metres wide around the equator.

What exactly is sand?

Geologists define it as grains of rock and mineral between 0.0625mm and 2mm across. On white beaches it is often composed of calcium carbonate, the ground-up remains of shellfish and coral. But most commonly it is made out of silica, or quartz, the second most abundant material in the Earth’s crust. Fine grains are formed by the gradual erosion of bigger chunks of rock by water, wind and ice, and are often swept down rivers from mountains to the sea. Many such rocks were themselves originally created by the lithification (i.e. compaction under pressure) of sand grains into sedimentary sandstone. “Perhaps half of all sand grains have been through six cycles in the mill,” writes the geologist Michael Welland in Sand: The Never-ending Story – “liberated, buried, exposed, and liberated again”.

Isn’t there a lot of sand about?

Yes. But unfortunately the desert sand covering much of the Earth’s surface is the wrong kind for construction: it is almost always rounded by wind erosion. Concrete requires “sharp sand”, with rough edges that give a resilient microstructure when mixed with cement and water. So the United Arab Emirates, for instance, imported $456m of sand, gravel and stone in 2014, from as far afield as Australia, to build the roads and skyscrapers of Dubai and Abu Dhabi – cities that are built on sand.

How is sand mined?

Until recently, it was mostly extracted from land quarries and riverbeds. However, the human demand for sand has exhausted many quarries and outpaced the natural replacement cycle. Vietnam’s government, for example, thinks the country could run out of construction sand by 2020. In China’s Shanghai region, sand, until recently, came from the bed of the Yangtze River. But by the late 1990s, mining had removed so much material that bridges were undermined and riverbanks collapsed. Sand mining was banned on the Yangtze in 2000. Then the miners moved to Poyang Lake, China’s biggest freshwater lake, 300 miles upriver: it’s now the largest sand mine on the planet, worked by hundreds of vast dredgers that can haul 10,000 tonnes of sand an hour. And as mining has deepened and widened its outflow, the lake’s water level has fallen significantly. Around the world, other types of habitats are also being destroyed as producers struggle to meet demand.

What kind of habitats?

Producers are turning to marine resources, even though dredging often does serious damage to sea life and fisheries. In the developing world, the business is often unregulated – or, if regulated, deeply corrupt. Half of all the sand used in construction in Morocco, says the UN, comes from illegal mining of beaches and coastal areas. India’s “sand mafia” runs an illegal trade worth $2.3bn a year, reports The Times of India. In Tamil Nadu, 50,000 lorry-loads are mined every day and smuggled to nearby states, while in the creeks near Mumbai, miners work in atrocious conditions (see box). In Kenya, illegal sand dredging is disrupting river courses and leaving communities without access to water. In Sierra Leone, extensive mining of beaches is blamed for coastal erosion of up to six metres per year. The demand for sand can also cause international tensions. Singapore has increased in size by over 20% since independence in 1965 by importing, and sometimes simply taking, sand from its neighbours to build on. Singaporean dredgers have been blamed for the disappearance of some 24 Indonesian sand islands.

Are there alternatives?

Plenty. Sand can be made by crushing sandstone. Industrial waste products such as coal ash, quarry dust, and copper and iron slag, which would otherwise be sent to landfill, can all be used as replacements for some of the sand in concrete. One recent Anglo-indian project found that waste from carrier bags can be substituted for 10% of the sand in concrete, while crushed recycled glass can replace it entirely. Concrete itself can be recycled. The difficulty is that all these processes are relatively complex, and the building industry is used to paying low costs to source and transport sand locally. Then there’s the sheer scale of demand. In 2014, it was estimated that India was using a tonne of concrete per Indian per year.

What is likely to happen in the future?

According to the industrial research group Freedonia, “sand and gravel reserves are shrinking across much of the world”, and as the construction industry in Asia continues to grow over the next decade, they’ll “be depleted at a rapid pace”. This, Freedonia surmises, will result in price hikes, particularly in urban centres, and lead to a shift to reasonably priced alternatives. But efforts to curb illegal mining, the report adds, have been “largely unsuccessful”. And in the meantime huge damage could be done. A recent study published in the journal Science predicts a “global sand crisis”, and warns that overexploitation of supplies is “damaging the environment, endangering communities, causing shortages and promoting violent conflict”.