Are solar panels less virtuous than petrol cans for the environment and human health? Photovoltaic panels, often seen as a clean and sustainable solution for energy production, are surrounded by urban legends, according to which they generate large quantities of toxic waste that is difficult to recycle. This false information has the unfortunate tendency to confuse the public, creating doubts about the viability of renewable energies.

However, solar panels are not entirely free of environmental impact. So are they really better than fossil fuels? To find out, several American researchers have examined some of the persistent myths surrounding solar panels in a commentary published in the journal Nature Physics. For example, the environmental cost of their production, the supposed deluge of electronic waste or the toxicity of the material for human and environmental health.

The real figures for photovoltaic waste

How much waste does the photovoltaic industry generate? In 2016, the International Renewable Energy Agency (IRENA) published a much-discussed report that drew attention to the potential problem posed by photovoltaic waste. The report estimates that the world could accumulate between 54 (low scenario) and 160 million tonnes (high scenario) of waste from solar panels by 2050.

Is that a lot? To find out, compare it to some other figures from the waste industry. By way of comparison, over 12,000 million tonnes of plastic waste and over 1,800 million tonnes of electronic waste will have been produced by 2050. By 2050, the fossil fuel industry will have produced more than 45,000 million tonnes of coal ashes and 249 million tonnes of oil sludge - not to mention greenhouse gas emissions. In other words, even in the most pessimistic scenario, the waste from solar panels represents only a fraction of the weight of that from fossil fuels.

More efficient... and greener solar panels

The manufacture of solar panels consumes resources such as silicon, silver, aluminium and cadmium telluride. It also requires energy, particularly if the materials are manufactured abroad and have to be shipped over long distances. Some solar panel manufacturers relocate their production abroad. However, some producing countries apply less stringent environmental standards. The carbon footprint of aluminium, lithium and silicon produced in Europe is well below the global average, according to a study carried out in 2022 by KU Leuven.

Significant technological advances have been made in recent years to increase the efficiency of solar panels. These make it possible to produce more energy with less material, which reduces the cost per installed watt and the weight of solar panels. They also reduce dependence on certain critical materials, such as silicon, copper and silver.

• Traditional solar panels, based on monocrystalline or polycrystalline silicon solar cells, required a substantial amount of pure silicon. However, new technologies have emerged, such as thin-film solar cells (amorphous, made of thin layers of copper, indium, gallium and selenium - CIGS), which require far fewer rare materials.
• More efficient manufacturing processes have reduced the need for inputs such as copper, silver and silicon. At the same time, the miniaturisation of electrical and electronic components in solar panels is also helping to reduce the amount of copper and other metals used in wiring and connections.
• New technologies such as perovskite cells promise to increase yields considerably.  
• New materials, such as conductive polymers used to capture sunlight in organic solar cells, limit the need for rare metals.
• Advances in panel design, anti-reflective coatings and cell structures have all contributed to this improvement.
• Photovoltaic trackers have also improved the efficiency of devices. These mechanical devices constantly adjust the angle and direction of the solar panels to follow the path of the sun throughout the day. This enables them to capture the sunlight optimally throughout the day, and generate up to 55 % more electricity than a fixed solar panel.

The challenge of recycling

End-of-life recycling naturally plays an important role in limiting the environmental footprint of solar panels. The metals they contain can be recovered through recycling, reducing the need to extract new resources. Today's photovoltaic solar panels are designed to have an average lifespan of around 25 to 30 years, but the industry is moving towards a lifespan of up to 50 years. Extending this lifespan means limiting the amount of waste produced each year.

In France alone, Soren, the eco-organisation responsible for recycling solar panels in France, have estimated at 150,000 tonnes between now and 2030 recycling needs. Contrary to popular belief, solar panels can be recycled to the tune of 99%. However, recycling is not always pushed to the limit, because it would be too expensive. As a result, the economic break-even point today is around 95% of materials recycled.

Toxicity in question

Among the arguments put forward against solar power is the idea that some of the materials used in photovoltaic modules accumulate in the environment and then cause damage to human health. Cadmium, in particular, which is used in certain solar technologies, is considered a definite human carcinogen by the International Agency for Research on Cancer (IARC). Associated cancers are those of the respiratory tract, particularly the lung. Cadmium is also suspected of being carcinogenic to the prostate and kidneys.

That said, the toxicity of materials is one thing, the risk of exposure is another. What are the risks of exposure to these products, compared with everyday electronic devices? According to an article published in the Renewable and Sustainable Energy Review, the actual risks to human health from environmental pollution from solar panels - from leaks in the rain, for example - are negligible. According to another study, there is a risk to human health when arsenic and beryllium are airborne. However, modern production methods have eliminated this risk.

In addition, the vast majority of photovoltaic modules are manufactured from crystalline silicon, which poses no health risk to the end user. In addition, the risks associated with the manufacturing process have been greatly reduced in recent years. This type of technology is by far the most common, with a 95% share of the world market by 2022.

What, if we had to replay the solar vs fossil match?

Let us return to our comparison between photovoltaic waste and that from the fossil fuel industry. In terms of toxicity, coal ash is far more problematic. It is considered to be highly toxic and carcinogenic to humans, as it contains a variety of heavy metals, such as lead, cadmium, arsenic, chromium, nickel and others. These heavy metals are toxic to human cells, disrupting their function. When they are released into the atmosphere, they are also transformed into fine particles that can be inhaled deep into the lungs. These fine particles are associated with serious respiratory problems and are also linked to an increased risk of lung cancer.

Throughout their life cycle, photovoltaic modules therefore pollute much less than oil or coal. Their widespread adoption as a means of reducing greenhouse gas emissions and combating climate change is essential both economically and in terms of human health.

See, Les panneaux solaires, fer de lance de la transition ou casse-tête pour le recyclage ? Le vrai du faux