Sand mining and recycling photovoltaics

Sand mining is an environmental problem that has often been overlooked. Sand is everywhere, and it’s easy to feel like there’s as much chance of “over-using” it as there is of over-using sea water.

That said, we use a vast amount of sand in this civilization of ours. Sand extraction for concrete alone is causing serious problems near where it’s mined:

Dr Chris Hackney at the University of Hull who led the research, said: “With the world currently undergoing rapid population growth and urbanisation, concrete production has grown massively, fuelling unprecedented demand for sand, so much so that sand is now the most consumed resource on the planet, after water”

The research was undertaken as part of a NERC funded project led by Professor Stephen Darby at the University of Southampton, which is studying the impact of climate change on the fluctuation of sediment through the Mekong.

Professor Darby added, “Much of the sand used in the production of concrete comes from the world’s big sand-bedded rivers, like the Mekong. There has long been a concern that sand mining from the Mekong is causing serious problems, but our work is the first to provide a comprehensive, rigorous, estimate not only of the rate at which sand is being removed from the system but how this compares to the natural replenishment of sand by river processes, as well as the adverse impacts unsustainable sand mining has on river bank erosion.”


Dr Julian Leyland of the University of Southampton, who performed the TLS surveys, said that “Our research showed that it only takes two metres of lowering of the river bed to cause many of the river banks along the Mekong to collapse, but we’ve seen that dredging pits can often exceed eight metres in depth. It’s clear that excessive sand mining is responsible for increased rates of bank erosion that local communities have been reporting in recent years.”

Dr Hackney warns that without proper regulation, excessive sand mining on the Mekong and other major rivers worldwide could have increasing environmental and social consequences.

As if the warming climate isn’t enough to be worried about. It probably shouldn’t be surprising that with the rise in demand for sand, there has also been an increase in illegal sand mining operations around the world. As Wired reports in their article on illegal sand mining and the violence surrounding it, desert sand isn’t good for construction because the grains are too smooth and round to bind well in concrete, so rivers and coastal regions become the biggest targets.

Apart from water and air, humble sand is the natural resource most consumed by human beings. People use more than 40 billion tons of sand and gravel every year. There’s so much demand that riverbeds and beaches around the world are being stripped bare. (Desert sand generally doesn’t work for construction; shaped by wind rather than water, desert grains are too round to bind together well.) And the amount of sand being mined is increasing exponentially.

Though the supply might seem endless, sand is a finite resource like any other. The worldwide construction boom of recent years—all those mushrooming megacities, from Lagos to Beijing—is devouring unprecedented quantities; extracting it is a $70 billion industry. In Dubai enormous land-reclamation projects and breakneck skyscraper-building have exhausted all the nearby sources. Exporters in Australia are literally selling sand to Arabs.

In some places multinational companies dredge it up with massive machines; in others local people haul it away with shovels and pickup trucks. As land quarries and riverbeds become tapped out, sand miners are turning to the seas, where thousands of ships now vacuum up huge amounts of the stuff from the ocean floor. As you might expect, all this often wreaks havoc on rivers, deltas, and marine ecosystems. Sand mines in the US are blamed for beach erosion, water and air pollution, and other ills, from the California coast to Wisconsin’s lakes. India’s Supreme Court recently warned that riparian sand mining is undermining bridges and disrupting ecosystems all over the country, slaughtering fish and birds. But regulations are scant and the will to enforce them even more so, especially in the developing world.

Sand mining has erased at least two dozen Indonesian islands since 2005. The stuff of those islands mostly ended up in Singapore, which needs titanic amounts to continue its program of artificially adding territory by reclaiming land from the sea. The city-state has created an extra 130 square kilometers in the past 40 years and is still adding more, making it by far the world’s largest sand importer. The collateral environmental damage has been so extreme that Indonesia, Malaysia, and Vietnam have all restricted or banned exports of sand to Singapore.

And as with all big sources of profit, people are being killed over sand. Photovoltaic panels are almost entirely made from crystalline silicon, which doesn’t require any particular shape of sand grain, to my knowledge, but it’s not uncommon for groups that specialize in something like extracting and selling sand to seek to monopolize emerging markets. Whether that will end up throttling the sand supply for solar panels remains to be seen. Furthermore, as with most technologies these days, there are materials involved in photovoltaics beyond silicon, including various hazardous materials. Solar power is going to be an ever-increasing portion of our society’s power generation, and being able to reuse the materials involved is crucial to extending the usefulness of that technology into the future, and to any effort to minimize the impact we have on the rest of Earth’s biosphere. Fortunately, that’s an area in which we are making progress, and researchers are starting to analyze efforts in that field.

Researchers at the National Renewable Energy Laboratory (NREL) have conducted the first global assessment into the most promising approaches to end-of-life management for solar photovoltaic (PV) modules.


The authors focused on the recycling of crystalline silicon, a material used in more than 90% of installed PV systems in a very pure form. It accounts for about half of the energy, carbon footprint, and cost to produce PV modules, but only a small portion of their mass. Silicon’s value is determined by its purity.

“It takes a lot of investment to make silicon pure,” said Silverman, PV hardware expert. “For a PV module, you take these silicon cells, seal them up in a weatherproof package where they’re touching other materials, and wait 20 to 30 years — all the while, PV technology is improving. How can we get back that energy and material investment in the best way for the environment?”

The authors found some countries have PV recycling regulations in place, while others are just beginning to consider solutions. Currently, only one crystalline silicon PV-dedicated recycling facility exists in the world due to the limited amount of waste being produced today.

Based on their findings, the authors recommend research and development to reduce recycling costs and environmental impacts, while maximizing material recovery. They suggest focusing on high-value silicon versus intact silicon wafers. The latter has been touted as achievable, but silicon wafers often crack and would not likely meet today’s exacting standards to enable direct reuse. To recover high-value silicon, the authors highlight the need for research and development of silicon purification processes.

The authors also emphasize that the environmental and economic impacts of recycling practices should be explored using techno-economic analyses and life-cycle assessments.

Finally, the authors note that finding ways to avoid waste to begin with is an important part of the equation, including how to make solar panels last longer, use materials more effectively, and produce electricity more efficiently.

“We need research and development because the accumulation of waste will sneak up on us,” Silverman said. “Much like the exponential growth of PV installations, it will seem to move slowly and then rapidly accelerate. By the time there’s enough waste to open a PV-dedicated facility, we need to have already studied the proper process.”

If successful, these findings could contribute one piece of a PV circular economy.

Hopefully this will lead to faster improvements in our capacity to recycle and reuse solar panels, and to reduce the demand for the extraction of new materials. We’ve got a lot of work to do, and any steps we can take to slow the rate at which we add to that needed work will be hugely beneficial in the long run. It’s “clean as you go” at a societal level.

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