07-07 sand

[Image above] Credit: Austin Ban; Unsplash

Back in 2017, I wrote a Ceramic Tech Today story about how a natural resource that might seem to be in abundant supply was perhaps surprisingly facing a serious scarcity.

That resource—sand—is one of the most consumed natural resources on our planet. Because in addition to being a primary component of beaches and deserts, sand’s tiny grains infiltrate nearly all aspects of our infrastructure—it is a critical component of concrete, asphalt, brick, and glass, for just a few notable and ubiquitous examples.

At the time of the CTT article, a Science perspectives paper had just been published that called for development of a global sand governance strategy to address the imminent threat of sand scarcity. 

“Current development trends suggest that sand demand will increase further in the coming years,” the authors wrote in the paper. “The resulting acceleration of sand extraction, trade, and consumption will have escalating effects on environmental and human systems. There is a pressing need for an effective global sand governance system.”

The authors were spot on—sand demand has continued to increase, and there are certainly escalating effects on environmental and human systems.

However, to understand the demand and the resulting effects, we first need to recognize an important fact—not all sands are created equal.

Desert sand versus ocean sand—what’s the difference?

Sure, the Sahara has enough sand to spew into the atmosphere and across the globe. But the sand found in deserts is different from the sand found in river beds, for example, because the sand grains form from different materials and via diverse processes.

Most desert sand particles are rounded because they formed from erosion and have been subjected to the brutal forces of wind. These rounded edges mean desert sands aren’t suitable for construction uses. In contrast, the more angular edges and frequent pores of sands found in places like river beds work better in construction applications, where they can better bind together materials such as concrete.

In terms of the materials that form sands, most sands are classified as either siliciclastic, meaning they contain silicate materials, or carbonate sands, which are rich in carbonate materials. Carbonate sands are typically found on seafloors because the sand forms from broken-down remains of marine creatures or from nonorganic processes, such as precipitation from carbonate-rich waters. Other kinds of sands instead form from erosion of rock, which is how siliciclastic sands are born.

That’s not to say all ocean sands are carbonate and all desert sands are siliciclastic, however—beaches can contain a mixture of both types of sands, for example. The important point is that not all sands are created equal, so different sands can be more suitable for different applications.

Sand demand: The scale of the problem

Sand grain differences aside, humans are still extracting a lot of sand across the planet for anthropogenic activities—and China may be leading the efforts.

“Around 60 percent of sand use worldwide is in China, which is estimated to consume more sand in three years than the U.S. consumed in the entire 20th century,” according to a 2019 Yale Environment 360 article.

But it’s surprisingly difficult to find accurate data to gauge the full extent of sand extraction and consumption activities worldwide.

Some estimates suggest that humans currently use some 50 billion tonnes of sand and gravel per year. And the sheer volume of those activities are bound to have serious consequences.

“We cannot extract 50 billion tonnes per year of any material without leading to massive impacts on the planet and thus on people’s lives,” Pascal Peduzzi, a researcher with the United Nations Environment Programme, says in a BBC Future article.

However, estimates such as 50 billion tonnes are often based on activity in the cement industry, which, while it consumes a large share of sand, only accounts for a portion of humans’ use of the resource.

Notably, such sand use statistics do not account for marine activities—see the “land reclamation” section below—because data on marine extraction of sand simply isn’t centrally collected, managed, or monitored.

So it’s difficult to quantify just how much sand countries are moving around the earth, stripped from some places and piled up in others. But it’s safe to say these activities add up to a lot of sand—much more than 50 billion tonnes per year.

And yet that global sand governance system that the 2017 Science article was calling for still remains a pressing need today.

Land reclamation: Redistributing the world’s sand

Land reclamation, also known as land fill, is the process of creating new land from oceans, seas, riverbeds, or lake beds. It is frequently used to rebuild land damaged by extreme weather events like hurricanes, to control continual erosion, or to provide some land safeguards against rising seas in the face of climate change.

However, land reclamation efforts also are frequently used to create land where there was none before—and such reclamation efforts by China in the past couple decades exemplify the environmental and geopolitical effects these activities can have.

To perform land reclamation, China has a substantial fleet of huge dredging ships that scrape the bottom of the ocean and suck up sand, water, and anything else along the way with giant centrifugal pumps. That sucked-up sand and more is collected in the ship’s hull, transported elsewhere, and spewed back out, reassigned to a new geography.

China has used dredging to create nearly 3,000 acres of new land around the Spratly Islands in the South China Sea within the past decade. But this fresh land isn’t meant to protect against rising seas or re-establish habitats—after creating the new land, the country promptly claimed its creation by topping the fresh sand piles with military bases.

“This expansion of Chinese power into the Pacific has alarmed the US as well as China’s neighbors,” according to an MIT Technology Review article. “To show it does not recognize the new islands as Chinese territory, the United States has made a point of flying B-52 bombers over them and sending warships to pass close by. For its part, China has landed long-range bombers on its new runways, as a show of force.”

In addition to raising tensions, these land reclamation activities also wreak environmental havoc, destroying habitats, wiping out living creatures, and completely altering natural landscapes.

“All that island building has also caused ‘devastating and long-lasting damage to the marine environment,’ according to the Hague-based Permanent Court of Arbitration, which rejected China’s claim to sovereignty over much of the South China Sea in 2016,” the MIT article continues. “Most plant and animal life on the seven Spratly reefs was destroyed by the mountains of sand dumped atop the coral. John McManus, a University of Miami marine biologist, called it ‘the most rapid rate of permanent loss of coral reef area in human history.’”

Of course, China is not the only country invested in such activities—many other countries around the globe have and do use dredging as a means of land reclamation as well, whether that land previously existed or not. For instance, “Singapore has created an extra 50 square miles of land, growing its size by 20 percent, thanks to more than half-a-billion tons of imported sand,” according to the Yale Environment 360 article.

Regulating sand: Quantification is such an aggravation

Before any sort of sand use or governance strategy can be developed, we need data to quantify just how much sand we are talking about—regulations would be of little use if there was no reliable way to gauge, monitor, and compare the scale of sand extraction and consumption activities.

This situation isn’t just a problem of not having anyone centrally accountable for collecting and monitoring sand consumption data, however—new research suggests we don’t even know how to accurately estimate the amounts and dynamics of sand itself.

Sediment dynamics, or how sand particles behave, may sound like a mundane field of study. But sediment dynamic models are really quite imperative as they help us to estimate the surface area of sand and thus sand volumes.

However, currently used sediment dynamic models often treat all sand particles the same, even though we know they are not. In particular, current models are based on data from round siliciclastic sand particles. But the same models are similarly applied to more angular carbonate sands, despite the known differences in shape, density, and porosity of the particles.

In a new open-access paper published in Scientific Reports, researchers from Turkey and Australia catalogued carbonate sand particles from a beach in Australia’s Great Barrier Reef and found that, although shape varies from particle to particle, an elliptical shape more accurately models the angular and irregular shapes of carbonate sands rather than round siliciclastic sands.

The researchers’ calculations showed that current models assuming a round particle shape incorrectly estimate the surface area of carbonate sand particles, and these differences are not trivial—the researchers say that existing models assuming a round shape can underestimate the surface area of carbonate sand by 35%.

That’s a big difference when you consider one grain of sand, but it is an even bigger discrepancy once you extrapolate to millions of tonnes of sand.

The researchers also used their new and improved models to show that the differences add up to considerable inaccuracies in the way that we estimate the dynamics of these sediments, accounting for up to 20% discrepancies in previous models.

“Keeping track of carbonate sand will become increasingly important,” study co-author Tristan Salles says in a Cosmos article. “If islands and atolls are at risk from erosion caused by sea-level rise, it will be vital to understand how the sands protecting them will respond to the ocean currents, waves and high-energy sea swells battering them.”

And similar logic can certainly be applied to the incredible amount of sand being shifted by human activities, like dredging sea floors and building new islands.

The paper, published in Scientific Reports, is “Improved drag coefficient and settling velocity for carbonate sands” (DOI: 10.1038/s41598-020-65741-3).

So what’s the solution?

Although we now have better models to more accurately estimate sand and predict its dynamics, the problem still remains—humans are extracting and consuming incredible amounts of sand around the globe, with little to no oversight and no end in sight. There’s still no global sand governance strategy, and getting countries around the world to agree to a solution seems like a nearly impossible task.

In the meantime, however, we can take steps to reduce sand consumption. The Yale Environment 360 article offers some ideas.

What should be done? Technically, some options exist. An untapped source of sand is the material that accumulates on the bottom of reservoirs. It could be dredged or flushed out. There is a win/win here. Dam operators would get the benefit of extra capacity for water storage, though arguably the sand should really be put back into the rivers it came from, rather than diverted for construction.

In developed countries, where new construction often replaces demolished buildings, there is untapped potential to recycle building rubble instead of using new concrete. A third of construction material for housing in the UK is already recycled. Glass recycling reduces that industry’s need for new sand. And there are substitutes for sand in concrete manufacture, including ash from power station incinerators, and dust from stone quarries. The problem is that at less than $10 a ton, sand remains very cheap.

The Hidden Environmental Toll of Mining the World’s Sand

Of course, these strategies can only go so far, especially in the face of dredging ship fleets moving mountains of sand from one place to another and ever-increasing infrastructure projects. Nearly impossible task or not, the authors of the 2017 Science article are still—and perhaps now more than ever—right: “There is a pressing need for an effective global sand governance system.”