After water, sand and gravel are the world’s most abundant resource.
In recent decades, the we have mined—and wasted––so much of it that the we’re actually running out of sand.
People have used sand for construction since prehistoric times. It is the chief component in glass.
Recently discovered processes also depend on sand. These include silicon chips for electronics and fracking.
Demand will continue to grow into the foreseeable future. And demand has begun to exceed supply.
What is sand?
The commonest form of silica, quartz, comprises most sand, but other substances make sand, too.
Hawaii’s black sands come from weathered obsidian, a volcanic glass.
The sand at White Sands National Monument in New Mexico is largely gypsum.
Sand at ocean beaches contains a high proportion of crushed shell—and increasingly, pulverized plastic trash.
Whatever it’s made of, sand results from the action of wind, water, and ice over time disintegrating larger rocks or other substances. Nature creates various shapes.
Strong wind blows grains of desert sand into each other so forcefully that the grains become rounded. River sand, being protected by a thin film of water, retains a more angular shape. Between these two, other sands are classified as sub-angular or sub-rounded.
According to the geological definition, grains of sand must measure at least 0.0625 mm. Anything just less than that is called silt. And sand grains can’t be any larger than 2 mm, or it becomes gravel.
What do we do with sand?
But developed countries only started to keep statistics about aggregate mining in recent years.
The paucity of data makes accurate environmental assessment of a sand shortage very difficult.
The top Google search results for sand mining all come from sites that seem to consider it an environmental menace that ought to be banned. Ban many mines, and we’ll be running out of sand even faster.
Statistics are available for the production of cement, a component of concrete. For every ton of cement, concrete requires six or seven tons of aggregate.
Global production of cement in 2012 was 3.7 billion tons. So the amount of aggregate needed for concrete alone that year may have exceeded 25 billion tons.
That doesn’t account for the amount of sand used for glass, silicon chips for electronics, solar panels, fracking, land reclamation, or road construction.
The first step in road building requires sand for the foundation, then coarser gravel on top of that. Asphalt contains a higher proportion of sand than does concrete. In addition to road beds, the construction of embankments requires still more sand.
Many uses for aggregate require specific characteristics.
For example, it’s not safe to play volleyball on ordinary beach sand. It’s too firm. Players are likely to suffer impact injuries like broken fingers or torn hamstrings.
So the sport of beach volleyball has its own specifications, developed for the 1996 Olympics. They control the size, shape, and hardness of individual grains of sand.
The specs forbid silt or other fine particles. It can stick to perspiring players. It can also fill voids between the grains and make the surface harder. Good sand for volleyball can’t make sand castles. It won’t clump.
Horse racing likewise requires special sand, although no single standard has yet been accepted. Horse anatomy requires a stiffer sand than what volleyball players play on.
Here’s some good news, sort of. We won’t be running out of sand in deserts. Its round grains make it useless for many purposes.
What is the environmental impact of sand mining and use?
World consumption of mined aggregates probably exceeds 40 billion tons annually.
That’s twice as much sediment as carried by all the world’s rivers.
We mine sand from quarries, sand dunes, beaches, river beds, and the ocean floor.
Extraction of such a large quantity of materials has unavoidable environmental consequences. Sand mining resembles any other mining. It digs into the earth’s surface to take something out of it.
Mining poses certain hazards both to the environment and to the health of workers and nearby residents. It can lead to erosion, degraded water quality, and diminished biodiversity.
On the other hand, buildup of sand causes problems for dams. Dam operators must release large amounts of water to flush it out. Mining aggregates from the dams is currently more expensive than other sources. But targeting this accumulation would both provide aggregate and solve problems for the dams.
Most of the developed world has environmental regulations that govern sand mining.
California has shut down its last coastal sand mine for environmental reasons. As demand begins to exceed supply, criminals have muscled into the industry, especially in the sand-hungry developing world.
Like everything else that seems in abundant supply, we waste sand. For example, the metal casting industry purchases sand to make casting molds and reuses it. Eventually heat and abrasion make it useless for casting molds. Therefore, foundries must regularly remove a portion of the sand and replace it with virgin sand. Foundries accumulate 6-10 million tons of spent sand every year. Spent foundry sand is useful for other purposes, including as a base for road beds or embankments or as a raw material in the manufacture of cement or asphalt.
The EPA estimates that foundries recycle less than 15% of their spent sand. In other words, they send at least 5 million tons of sand to landfills.
That’s only one industry, which uses much less sand than others. No wonder the world has a sand shortage!
What are useful alternatives to sand?
Sending construction rubble to landfills likewise wastes sand as much as it wastes landfill space.
Crushed concrete from demolished buildings, streets, and sidewalks could make new aggregate.
Quarry dust, incinerator ash, and crushed glass make suitable aggregate for some purposes.
Perhaps the most creative way to replace sand at least some of the sand in the manufacture of concrete is to use plastic waste for aggregate.
Concrete with plastic aggregate can be any color, depending on the color of plastic used. It could therefore provide visual interest to basement floors or patios.
The world is running out of sand, nature’s most abundant solid, for commercial purposes. And wasting too much of what it uses.
If you don’t work as an officer in a company that uses sand, there’s not much you can do about the sand shortage directly. But you can watch your own habits so that you waste as little of anything as possible.
Foundry sands recycling / US Environmental Protection Agency. April 2007
Plastic aggregate / Joe Nasvik, Concrete Construction, May 1, 1991
Sand, rarer than one thinks / UNEP Global Environmental Alert Service (GEAS). March 2014
The world is running out of sand / David Owen, The New Yorker. May 29, 2017
Coquina Beach and North Head. My photos
Concrete sidewalk. Photo by Famartin. Public domain from Wikimedia Commons
Solar Valley Micro-E Hotel. Source unknown
Fly ash bricks. Photo by Thamizhpparithi Maari. Public domain from Wikimedia Commons