One company has a seemingly simple plan to help save the planet: take a food additive and the mineral that gives eggshells their hardness, create nanoparticles from them, and then spray those particles into the atmosphere to cool the world.
Stardust Solutions, an Israeli-American company founded in 2023 and led by two nuclear physicists who formerly worked for the Israeli government, seeks to advance the race to develop “solar geoengineering,” a controversial technology that aims to artificially lower global temperatures by reducing the amount of sunlight that reaches the Earth.
There are many different methods of solar geoengineering, but the most researched is the method that Stardust is focusing on, which involves spraying ultrafine particles into the stratosphere using high-altitude planes or balloons, with the aim of reflecting the sun's energy away from Earth and back into space.
This process is an artificial version of a natural phenomenon. Sometimes, volcanic eruptions spew huge amounts of sulfur dioxide into the atmosphere, which can temporarily lower global temperatures.
In 1991, the eruption of Mount Pinatubo in the Philippines pumped enough sulfur dioxide into the atmosphere that temperatures dropped by 0.5°C (0.9°F) for more than a year.
As humans continue to burn fossil fuels and cause the planet to warm, interest is growing in the question of whether solar geoengineering can be moved from theory to practice.
Yanai Yedvab, CEO of Stardust, said that this technology represents a “very important tool” that governments should take into consideration in light of the alarming rise in global temperatures, but he stressed that it is not a magic solution to the problem of climate change, nor a substitute for addressing its root causes.
However, many scientists have expressed concerns that solar geoengineering could lead to catastrophic global repercussions, such as radical changes in weather patterns. Some experts also warn that a for-profit company developing a proprietary technology could have huge and unpredictable consequences.
Raymond Berhumbert, professor of planetary physics at the University of Oxford, said: “When the whole world is at stake, meeting the profits of venture capitalists should never factor into decisions about whether and which technologies to use.”
Scientists have been studying solar geoengineering for decades, but private companies are beginning to emerge in this field. Among the most prominent is “Stardust,” which is considered the best funded, having raised $75 million from investors.
The company was established in the wake of the Corona pandemic. Yadfab and his co-founder Amiyad Spector came up with the idea of working in solar geoengineering while looking for ways to help address the climate crisis.
In terms of spraying particles into the atmosphere, most solar geoengineering research and development focuses on sulfur dioxide, trying to simulate the effects of volcanic eruptions. But sulfur dioxide can have negative effects, including contributing to the formation of acid rain and depleting the ozone layer.
Stardust wanted to develop a material that was “better, safer and more controllable,” Yedfab explained. Earlier this year, the company revealed its particle designs in a series of scientific papers that are still awaiting peer review.
The company produced two types of particles: the first was made of amorphous silica, which is commonly used as an anti-caking additive in foods, toothpaste and cosmetics, while the second consisted of a core of calcium carbonate, the main component of egg shells, surrounded by a shell of amorphous silica.
Both compounds exist naturally, but can also be produced synthetically. Yedfab pointed out that they are among the commonly used materials. For example, amorphous silica was released into the New York City subway in 2016 as part of a test conducted by the Department of Homeland Security to simulate the effects of a potential biological attack. Yedfab believes that this incident helps clarify the extent to which silica is considered a safe material.
Every million tons of particles could reduce the temperature by about 0.5 degrees Celsius, and this amount would have to be replenished annually, Ydvab noted. The cost of deploying each million tons will amount to about 10 billion dollars. He acknowledged that it was a huge sum, but it was still a small fraction of the amount of damage actually caused by climate change-related disasters.
However, experts have raised a number of concerns. In addition to concerns about private companies trying to modify the climate, some are concerned about the potential impacts on global climate and weather, as well as on human health.
For his part, David Keith, a professor of geophysical sciences at the University of Chicago who is known for his research on solar geoengineering, said that Stardust “is greatly exaggerating when it says it is confident that the risks (of its particles) are less than those of sulfur.”
Among the concerns is what is known as the “hitchhiker hypothesis,” an idea that particles in the air may pick up metals or other materials that can cause harm when inhaled by humans.
Stardust explained that the design of its particles takes these risks into account. But Kelly Wanser, executive director of the climate research nonprofit SilverLining, said it's still unclear whether these particles would work when used on a large scale, and how they might behave within the atmosphere.
“Solar geoengineering addresses some of the least understood aspects of the climate system,” Berhumbert said, adding that any small-scale experiment cannot reveal how Earth's systems will respond to a large-scale deployment.
So far, the company's testing has been limited to the laboratory. External testing represents the next step, but past experience indicates that this stage may be very complex and controversial.
Plans by Harvard scientists to conduct solar geoengineering test flights in the polar region of Sweden were canceled in 2021, after strong local opposition. A controversial experiment conducted by US startup Make Sunsets in Mexico in 2022 also led to the country banning solar geoengineering experiments.
Stardust hopes to begin external testing within the next few years. Yedfab said that the company will only conduct these tests “under the supervision and direct guidance of governments.”
However, Stardust is a for-profit company with a financial interest in using this technology, according to some experts, which has raised concerns.
“Proprietary technology and profit motives are in direct conflict with the level of transparency needed to legitimize (solar geoengineering) research,” Keith wrote in a blog post last year.
But the risks here are very serious. Scientists say solar geoengineering could open the door to a wide range of unintended consequences, including potentially changing rainfall patterns and shifting monsoon systems, which could have major implications for food production.
Perhaps the most worrying possibility is what is known as a “termination shock,” meaning that once solar geoengineering begins, it may have to continue indefinitely.
Berhumbert said that if the process stopped suddenly, "the world would find itself facing a catastrophic and sudden rise in temperatures that will occur in just a few years."
Stardust says the impact of its technology can be scaled up or down, meaning deployments can be gradually reduced. Particles fall out of the atmosphere after about a year, “so the level of cooling remains an ongoing and adjustable option in the hands of governments, and a termination shock can be avoided,” Ydvab said.
But some are still not convinced. A recent study concluded that the use of this technology would lead to “deep system-level uncertainty” and “potentially further destabilize the global climate system.”
There are also concerns that this technology will be used as an excuse not to make significant cuts in planet-warming pollution, which would require a significant reduction in the amount of fossil fuels we burn.
