Posted on July 29, 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’.
An aerial view of Straits Quay Marina Bay in Malaysia, formed with sand reclaimed from the ocean
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.
On 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.
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.’
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.’
Large vessels can dredge sand from the bottom of the sea, leaving plumes behind them
Source: geographical.co.uk
