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Sand: is the extraction of the world’s most-mined commodity sustainable?

Sand is one of the main components of concrete, making it a resource in very high demand Sand is one of the main components of concrete, making it a resource in very high demand
28 Jul
2020
Sand is the single most mined commodity. Used to make concrete, its extraction eclipses other metals and minerals by a huge margin. Yet while it is abundant, it is not infinite. Fears that some sand deposits are being overused, combined with increasing evidence that the dredging of rivers and seafloors causes vast damage to ecosystems and coastal communities, bring the sustainability of this vital material into question

At the end of May 2020, when workers at the new nuclear reactor at Hinkley Point C began to pour concrete, they didn’t stop for three days. A time-lapse video shows 12-foot mechanical arms hovering over the disk that would form the reactor base, setting it in sections like an enormous 3D printer. While exact formulas for concrete are often trade secrets, the main ingredient is aggregates: gravel and sand. Looking out at the beige megaproject from Burnham-on-Sea – which, with the second longest tidal range in the world, appears as an endless beach at low water – you’d never think we need be worried about using too much sand.

The Hinkley pour (the second of two) is the largest continuous concrete pour ever to take place in the UK. Its 9,000 cubic metres of concrete base broke the Shard’s record of 5,500 cubic metres set in 2013. These records are dwarfed, however, by the global competition. The last three years saw Russia’s lofty Lakhta Center’s record of 19,624 cubic metres swiped by the Jebel Ali residential development in Dubai with 21,580 cubic metres, which in turn was shot out the park by India’s Polavaram Dam, a structure that spanned the Godavari river with 32,500 cubic metres of concrete. Meanwhile, huge development growth in China meant that the country got through more cement between 2011 and 2013 than the US did in the entire 20th century.

The use of sand for such mega projects, combined with its use in more basic construction, road building, beach nourishment as well as glass and computer chips means it is the most traded commodity by volume, after water. Mining takes place across the world and is dug from pits on land, dredged from riverbeds, and scooped up from the seabed. The UN estimates that we use 40-50 billion tonnes of the material a year, enough to cover the continent of Africa in a layer of sand a milimetre thick. It is already responsible for 85 per cent of all mineral extraction, and rates of extraction are increasing. Pascal Peduzzi, the UN’s voice on sand, warns that ‘we are approaching a future where access to this resource is a critical barrier to sustainability, and the full costs of uncontrolled extraction come due’.

cityscape sandAn aerial view of Straits Quay Marina Bay in Malaysia, formed with sand reclaimed from the ocean

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HIDDEN PITS

It’s July 2014, and from the palm-lined riverside of Phnom Penh, it’s possible to see sand dredgers at work. In the triangle of water where the Tonle Sap river empties into the Mekong, under the shadow of a new luxury hotel, dozens of vessels go back and forth.

Drifting among these vessels is an imposter. It’s a tourist cruiser, though today it’s home to scientists. On board, Dr Chris Hackney, a visiting academic in geomorphology at the University of Southampton, tries to mow even lines across the river. He wants to create a sonar map of the mining taking place three metres beneath the surface. Given the amount of activity, he knows the results could be big.

Hackney is first and foremost a river researcher. Before heading to the Mekong he hadn’t given sand much thought, ‘no more than the rest of us’, he says, ‘it always seemed abundant’. But it was through studying rivers, and their role in the transport of sediment, that he was put to the task. According to the UN, rivers and glaciers shift 24 billion tonnes of sand every year in what constitutes the largest natural movement of material in the world. But it’s still half of the 50 billion tonnes humans are shifting. 

It was when he first arrived at Phnom Penh that Hackney began to see the link between development and river sediment. ‘Immediately you can see the sheer amount of river activity,’ he says, describing scenes of 10 to 20 barges within a one kilometre stretch. His final study joined a growing chorus of locals and scientists concerned about the impact of this on nearby locations.

MekongOn the banks of the Mekong River in Phnom Penh, houses lie close to the water's edge

The trends are certainly worrying. For the past decade, bank erosion has increased along the Mekong – roads, homes, even temples are being claimed by the river in ever larger chunks. ‘Homes built in the 1980s, dozens of metres from the river’s edge are now practically on top of the water,’ says Alex Gonzalez-Davidson, co-founder of Mother Nature Cambodia, the most vocal NGO on the issue. ‘It’s a threat to lives and livelihoods.’

The solution seems obvious – reduce sand mining. But there are two challenges. The first is that sand dredging is licensed by the Cambodian government.

Mother Nature argues that there are high levels of corruption, which ‘encourages miners to take out higher than their licensed share’. But tight-lids are kept on the licenses. ‘Even if people stuck to them, we don’t know that extraction rates would be more sustainable,’ says Gonzalez-Davidson. ‘What we do know is there is sand dredging everywhere and what we do know is that river bank collapse is mind boggling.’

The second challenge lies in proving that sand mining causes the bank erosion in the first place. ‘The Mekong is heavily damned,’ explains Hackney. For the past decade, bank erosion has been mainly attributed to the damming, while the increase in mining has gone relatively under the radar. ‘All the different activity means it’s hard to link a bank collapse to sand mining, or even a specific mine in particular.’ He needed to be able to prove that mining, specifically, could cause a bank to collapse.

Recyling sand
There are alternatives to using virgin deposits of sand to create new concrete. In developed countries, older buildings are frequently replaced with new construction and there is potential to recycle building rubble instead of using new materials. Japan, which banned marine sand mining in 1990, has created a method for fine sand production by crushing quarry waste. The manufactured sand is now used extensively in construction projects.

In the UK, about one third of construction material for housing is recycled. Recycled glass, for instance, can be turned into sand. In concrete making, the sand can also be substituted with other materials such as ash from power station incinerators. The problem is that at less than $10 a ton, sand remains very cheap, lowering the incentives to recycle old material.

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When Hackney’s results were published this spring, they revealed a sinking world beneath the water. Gonzalez-Davidson, who saw them, was stunned. ‘It showed massive pockets,’ he explains. The sonar mapped out honeycomb holes in the bed, some as deep as two double-decker buses stacked on top of each other and 70 metres wide. If the water in the Mekong was to suddenly disappear, the city would be overlooking an enormous open pit mine.

Sonar of the river’s natural dunes showed that about six million tonnes of sand comes downriver every year. Dredgers are taking out 50 million tonnes per year. ‘This means it is being removed about five to nine times faster than it can replenish,’ says Hackney. And it’s probably being removed even faster. ‘The 50 million tonnes figure comes from a study interviewing dredgers themselves in 2013,’ Hackney says with a dry laugh, ‘you can imagine it’s a conservative estimate. And demand has likely increased in the seven years since the study was conducted.’

The stark difference in the two figures – between what gets taken out of the river verses what comes in – helped prove that sand mining can cause bank erosion. ‘Sand mining causes banks to become unstable and collapse,’ Hackney concluded in the paper.

More than ever, Hackney now notices the dramatic change in Phnom Penh’s skyline. ‘You start putting two and two together and you realise that all construction needs this material. River mining is banned in Europe, so it makes you wonder where all the material has come from – and where it will come from in the future.’

Biodiversity issues
There has been a growing chorus of concern for the ecosystems left behind once dredging is done. The seafloor is an important habitat for meiofauna – small marine invertebrates, which are crucial to the food chain – and provides spawning grounds for fish such as herring, sole and cod. According to marine biology studies, dredging gravel removes these habitats completely, while dredging sand creates disruptive plumes, which are suspended in the water column and can smother surrounding habitats.

‘The fall out is wide and catastrophic,’ says Stephen Eades, director of Marinet, a marine environment campaign group. ‘The complexity of these old riverbeds are equal to that of an ancient woodland. Once it’s gone it can’t be replicated.’

Dr Vera Van Lancker, a specialist in geological science at the Royal Belgian Institute of Natural Sciences agrees: ‘Sand dredging can never be truly sustainable as the material that is removed does not replenish.’ While extractions require environmental impact assessments, Marinet argues that they favour businesses and are not fit for purpose. As it stands, aggregate dredging is permitted within the UK’s marine conservation zones.

EUROPE'S SAND FACTORY

Stand on the coast of Great Yarmouth and you can often spot the outline of industrial ships moving across the grey distance. To visitors, this section of the North Sea is best known as a terminus to the Norfolk Broads. The ocean view is the open, rolling credits at the end of the inland beauty spot. To the sand industry, it’s Area 240, one of the most productive sand mines in the North Sea.

Up close, a North Sea dredger is a mammoth of welded metal. Most vessels carry two drag heads, each one the size of a small car, which sink their teeth into the seafloor eight metres underwater. These heads are attached to long arms bent over the deck like tense haunches, giving the vessel the look of an enormous steel cricket. When the pumps switch on, liquid churns into the hollowed container – or hopper – in the deck. Once the tub is full of hissing sand and seawater, the vessel looks half floating, half flooded.

The desired material is ancient river sand, the old bed of the River Yare. Twenty thousand years ago, what is now seabed was low-lying flood plain. The Yare and other southern rivers, such as the Stour and Thames, moved across this land towards Holland, forming a confluence with the Rhine, which left for the Atlantic via the channel. Today, heavy operations by North Sea countries scoop up their share of this ‘fossil’ sand. The UK, for instance, now gets up to a quarter of its sand from the seafloor. Sometimes, mammoth vessels bring up real mammoth remains – fragments of jaw bone; bits of skull. Dredging companies say they have never found a complete mammoth skeleton, though you can’t help but wonder what a drag head would do to one if it did.

North Sea dredging has transformed over the last thirty years. Traditional artisanal boats with capacity of 1,500 cubic metres, which hugged the coast, have bloated into 15,000-cubic-metre vessels with the ability to mine much deeper water and make many more trips. ‘And the activity is going to upscale again,’ says Dr Vera Van Lancker, a specialist in geological science at the Royal Belgian Institute of Natural Sciences. ‘In any scenario there will be tremendous increase in the sand demand. It will begin to create pits underwater the likes of which you see on land.’

Ship sandLarge vessels can dredge sand from the bottom of the sea, leaving plumes behind them

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Where is this sand going? A drive for energy-efficient architecture in Europe will spur a construction boom. The big ticket however is large beach nourishment projects and the creation of off shore islands. ‘Sea level rise is a ticking clock for many North Sea communities,’ says Van Lancker. ‘Enormous amounts of sand will need to be extracted to nourish and protect coasts.’ Some countries are also talking of creating off shore island hubs for the wind industry, ‘which will require even bigger volumes still’. In 2018, the North Sea countries extracted 41.3 million cubic metres of sand. A study in Denmark found that a single island hub will require twice that amount.

Outside of Europe, similar projects are taking place. Singapore has already created an extra 50 square miles of land, growing its size by 20 per cent, thanks to more than half a billion tons of imported sand. Land reclamation is taking place from Malaysia and the Philippines to Dubai and China (where 60 per cent of sand use worldwide takes place).

In developed countries, there is some regulation to combat the risks. ‘The North Sea bordering countries have a strong regulatory system, and together the region is beginning to recognise that this is no longer an infi nite mass,’ says Van Lancker. But she warns that sand could still run out if we are not careful. ‘Th at’s the interest from geologists – to try and deliver the best possible knowledge on where the good reserves are, so we can be more careful with what we use and how much of it.’

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SingaporeSingapore's famous Gardens By The Bay park spans 250 acres, all of which is reclaimed land

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THE WORLD'S LOCAL PROBLEM

In March this year, a satellite monitoring team called C4ADS noticed some strange activity in Haeju Bay, North Korea. Beginning in early 2019, the bay’s usually lonely waters began to fill with a line of industrial vessels, moving together in convoy, as though answering a signal only they could detect. The vessels had common characteristics. They all came from Chinese waters, all lacked IMO numbers (a kind of number plate for ships with international routes) and all seemed to be kitted out for dredging. As the fleet went back and forth for six months, tell-tale sand plumes curled under the vessels, while cargo ships arrived empty and left full. It stank of a coordinated sand mining campaign.

If the team are correct, it means that North Korea violated UN sanctions that prohibit it from supplying, selling or transferring sand. ‘It would represent the most sophisticated illicit sand mining so far,’ says Aurora Torres, a postdoctoral fellow at the Université Catholique de Louvain in Belgium. The exchange could have been worth at least £18 million to North Korea.

Torres studies the illicit sand trade. Her research documents reports of sand mafias in East African countries such as Kenya, where violent gangs protect mines, and in India – the world’s second-largest sand mining country (below China) – where widespread illegal extraction is aided by bribery and corruption. The more sophisticated of these operations led to numerous problems for local communities including environmental damage, loss of fisheries and loss of potential tax revenue. Torres is less worried about a scarcity of sand than about the impact of mining on society. ‘This is a globally abundant resource,’ she says, ‘running out is less of a concern than the social, economic and environmental threat.’

This highlights that the conditions under which mining takes place, and the exact locations, are important. Yet there are no global treaties governing sand extraction, use or trade. Most sand experts accept that some sand extraction is a necessary evil of development, particularly as it is needed for developing countries and for climate change mitigation, but they stress that it must be better regulated. ‘We’re not all of a sudden going to stop needing it,’ says Hackney. ‘It’s going to be a livelihood for hundreds of thousands of people around the world – but that means it’s important to get it right.’

‘If mining is to happen we need to ask for whom the extraction is occurring, and if it is vital,’ Torres adds.

Though the overuse of sand is a global issue, the illicit trade is a remarkably local one. A recent UN report estimated that less than five per cent of extracted sand and gravel moves across borders. The simple reason? It’s heavy. ‘That’s the general rule for construction materials,’ says Torres, ‘you need to find them as close as possible to the place you need them to cut transport costs.’ Even the exceptions, such as trade between North Korea and China, is usually neighbour-to-neighbour. 

This means that sand supply chains are short compared to many other minerals. ‘The problem is global, but the governance solutions are local,’ explains Pascal Peduzzi, the UN’s voice on sand sustainability. This often leads to weak regulation and weak enforcement. Tightening of both is essential.

Van Lancker agrees. ‘Even in the North Sea, where there is regulation, we need to be as discerning as possible. People need to be able to weigh up whether a development is worth the heavy extraction.’

For Hackney, these questions need to be asked more often, before it’s too late. ‘If water or oil was governed in the same way as sand, there would be global outrage,’ he says.

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