The World Needs More Sand, But Reclamation Poses Challenges
Sand seems to be one of the Earth’s most ubiquitous and abundance resources, whether it graces endless beaches or lies hidden in towering buildings and miles of pavement.
The truth is more complex. The world’s demand for sand is constantly escalating; however, sand “is being used faster than it can be naturally replenished, so its responsible management is crucial,” says a 2022 UN report.
Enter the challenging world of sand reclamation. The benefits are readily seen: Sand is essential for economic development, homes, roads, hospitals and industry, and also to fortify beaches and coastal areas to preserve biodiversity and fragile ecosystems.
But improper sand reclamation tactics can also have catastrophic impacts on the environment, such as when river banks are damaged in the recovery process.
The Exploding Need for Sand
In 2019, a team of scientists from Denmark and the US released a study revealing that the global demand for sand was 9.55 billion tons, or about $99.5 billion, in 2017. A subsequent report by the United Nations Environment Programme (UNEP), published in April 2022, estimated that a global total of 40 billion to 50 billion metric tons of sand was being used every year. Fifty billion tons is “enough to build a wall 27 meters wide [about 30 yards] and 27 meters high around planet Earth … making [sand] the second most used resource worldwide after water,” the report noted.
[N]atural sources [of sand] are now heading toward depletion—with an estimate that the world will run out of construction-grade sand by 2050—thus making sand reclamation and alternative sources of utmost importance.
The huge demand for sand is being fueled by the growth of cities and construction industry. This means, in turn, that natural sources are now heading toward depletion—with an estimate that the world will run out of construction-grade sand by 2050—thus making sand reclamation and alternative sources of utmost importance.
Properties of Sand and its Applications
Sand consists of finely divided mineral particles of various compositions. It is defined primarily by its grain size, distinguishing it from gravel, which has larger grains, and silt, which is finer and smoother. For example, the Unified Soil Classification System used in engineering and in geology defines sand according to US standard sieves, i.e., with a diameter of between 0.074 and 4.75 millimeters. Another definition, applied by geologists, concerns particles ranging in diameter from 0.0625 mm (or 1⁄16 mm) to 2 mm.
On inland surfaces and on non-tropical coasts, the most common element of sand is silica (silicon dioxide, or SiO2). This is because it is usually mostly made of quartz, and its chemical inertness and hardness renders it resistant to weathering.
Silica sand is what is used in a mobile device’s glass screen—as well as computer chips, fiber-optic cables, and other hardware—which makes iPhones and computer displays possible.
Silica is also used to make frac sand, which is used for hydraulic fracturing (“fracking”) in oil and gas extraction.
Silica sand is what is used in a mobile device’s glass screen—as well as computer chips, fiber-optic cables, and other hardware—which makes iPhones and computer displays possible.
In tropical areas, the bright white sand found on coastlines is formed from eroded limestone and may also contain fragments of shell and coral alongside other organic material. White sand is often blended with concrete to create a bright and attractive appearance for use in places such as golf courses, volleyball courts, and inland beaches.
Can Desert Sand Be Reclaimed?
What about the sand in the Sahara and other vast deserts? Sadly, there are two major reasons why, despite its abundance, desert sand is not suitable for construction purposes.
The first is that the sand grains are rounded rather than being course and angular. This tends to make cement less cohesive. Furthermore, desert sand can have high salt content, which tends to weaken concrete and exacerbate corrosion of steel.
While research is being done to implement desert sand into cement-based materials, river sand remains the primary source of sand for the construction industry.
Drawbacks of Sand Mining
The UNEP report found that extracting sand from rivers and in coastal or marine ecosystems can lead to significant adverse impacts. These include “erosion, the salination of aquifers, weakened protection against storm surges, and adverse impacts on biodiversity.”
The UNEP report found that extracting sand from rivers and in coastal or marine ecosystems can lead to significant adverse impacts. These include “erosion, the salination of aquifers, weakened protection against storm surges, and adverse impacts on biodiversity.” These, in turn, might negatively affect water supply, food production, fisheries, and the tourism industry.
Furthermore, dredging [see The Earth & I, June 2024] kills marine life in the river or lake and causes environmental impacts that can last for years. This not only adversely affects the fishing industries and coastal communities, but extraction of sand can also erode shorelines, damage infrastructure such as bridges, and threaten forests.
Sand Reclamation and Reuse
In their 2022 study, researchers E.S. Rentier and L.H. Cammaraat point out that there are a number of things that can be done to minimize the impact of river sand mining on the environment and protect ecosystems:
Recover sand from sustainable sources, such as from retreating ice sheets in Greenland, which do not damage rivers. This would require sand auditing to construct an inventory of the available sediment.
Establish global guidelines on where extraction of sand resources is not sustainable, as well as an international framework to regulate and control sand mining.
Establish a mandatory global program to monitor sediment mining.
The US Environmental Protection Agency has adopted a solid waste management hierarchy that promotes waste reduction, recycling and reuse. It cites as an example the use of spent foundry sands from iron, steel, and aluminum plants.
These facilities tend to reuse sand many times over, but eventually heat and mechanical abrasion render the sand unusable for casting molds. At present, about 15% of the 6 million to 10 million tons of spent foundry sands generated annually is recycled.
At present, about 15% of the 6 million to 10 million tons of spent foundry sands generated annually is recycled.
Resand’s Process
A foundry sand recycling company in Finland has been improving sand reclamation processes for more than 15 years.
“In the reclamation process, all the sharp edges and corners are smoothened or removed from the sand grains and that creates many benefits: better surface quality of the castings, better gas permeability in casting process, [and] better flowability of the sand when filling the sand molds,” explained Jukka Nieminen, executive vice president of Resand Ltd.
It all started in 2008 with a collaboration with Finnish foundries providing metal recycling services for foundries.
“Soon we found out that foundries had difficulties with used sand disposal,” Nieminen said. “Foundries asked our help, and in 2016 we started a project with our customer foundries and Aalto University, and we started to make sand reclamation trials,” she said. “At that same year, we acquired an old glass making factory from Nuutajärvi, Finland, where we are operating today, and there was sand treatment equipment that we modified so that we were able to start making trials with our customers.”
Now aided by a €3 million (about $3.2 million) loan from Nefco, a financer of environmental projects, Resand recently said it will accelerate the expansion of its services through its Sand As A Service (SAAS) solution, which it says will enable foundries to reduce virgin sand consumption by 75%.
Resand’s modular sand reclaimer processing unit consists of two rotating drums: a heating drum and cooling and separation drum [see video].
“In the heating drum, the temperature of the sand is between 600–800 degrees [Celsius], and in these temperatures all organic binder burns, and in the second step we cool the sand close to ambient temperature so it can be used again immediately,” Nieminen said. “We also remove all the fine dust particles so the sand is totally dust free and clean for the reuse.”
Resand also claims that their electrically powered recycling process reduces overall carbon dioxide emissions for new sand by up to 70%, with a production capacity of 1,000 kg (or 1.1 tons) per hour.
This is why the Resand technology is contributing to a green transition in the foundry industry, said Här Kalle Härkki, CEO of Resand Ltd.
*Robin Whitlock is an England-based freelance journalist specializing in environmental issues, climate change, and renewable energy, with a variety of other professional interests, including green transportation.
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