Photovoltaic technology, commonly referred to as solar technology or solar energy, is widely regarded as a zero carbon, sustainable and renewable generator of energy (Tawalbehe et al 2021). PV systems have zero emissions of carbon dioxide, methane, sulfur oxides, and nitrogen oxides (CO2, CH4, SOX, NOX, respectively) during operation with negligible effects on air pollution and climate change (Segura et al. 2023). As mentioned in another Minviro blog on Solar Photovoltaics in the Energy Transition, solar photovoltaics currently make up 5.4% of the global electricity generation and are projected to increase sixfold in the next decade (IEA, 2024).

The United States, India, and China are prominent countries currently adopting solar energy harvesting technologies (IEA, 2024). Additionally, countries such as Japan, India, Brazil, Australia, and the United Arab Emirates have made significant investments in solar energy technologies with the UAE, for instance, constructing the world's largest concentrating solar power plant in 2018 (Tawalbehe et al 2021).

Undeniably, PVs offer significant potential for reducing greenhouse gas emissions and global dependence on fossil fuels. However, although PVs can generate renewable energy, the wider environmental impacts of the supply chain of the technology itself, when taking a lifecycle approach across raw material extraction, manufacturing and end of life, can be significant. Understanding the environmental impacts of PV supply chains across from a lifecycle perspective is crucial for evaluating the overall sustainability of solar systems.

Raw Material Extraction and Manufacturing

PVs are made from a range of semiconductor and other raw materials that need to be mined and extracted. The most commonly used material in solar panels is silicon. Silicon is abundant, but its extraction and purification are energy-intensive processes. The mining of silicon, quartz sand, as well as other used materials like silver, aluminium, and copper can have significant energy, water and chemical resource demands in addition to land transformation impacts that can all lead to soil pollution, water pollution, habitat destruction and biodiversity losses (Stamford & Azapagic, 2018).

Rare earth elements and other critical metals such as cadmium (used in cadmium telluride cells) and indium (used in copper indium gallium selenide cells) also play crucial roles in certain types of non-Silicon PVs. Mining and refining these metals often involve harmful chemicals, leading to hazardous waste and emissions. For instance, cadmium is a toxic heavy metal, and improper handling can pose severe health and environmental risks.

The manufacturing stage of photovoltaic cells and modules is another significant contributor to environmental impacts. The use of hazardous chemicals in manufacturing, such as hydrofluoric acid, sodium hydroxide, and other etching and doping agents, poses risks to workers and the environment if not properly managed. These chemicals can lead to water and soil contamination if disposed of improperly.

Silicon purification, ingot and wafer production, cell processing, and module assembly are energy-intensive processes. The primary energy source for these processes often comes from non-renewable sources, leading to substantial greenhouse gas emissions. The carbon footprint of PV module manufacturing can be considerable, although it is generally lower than that of fossil fuel-based energy production over the entire lifecycle of the system.

Importantly, while the use of PVs is inherently greenhouse gas emission-free, the mining and processing of PV materials and the manufacturing of the panels is not. According to the IEA tracking report released in 2022, the CO2 emissions for the production of PV systems ranged from 14 to 73 g CO2-eq/kWh, depending on the PV technology, the location of the power plant, and the electricity mix used for the production (IEA, 2022).

Installation and Infrastructure

The installation of PV systems involves land use changes, particularly for large-scale solar farms. Land use impacts can include habitat disruption and changes in land cover, which can affect local ecosystems. However, the use of previously disturbed or low-value land, such as brownfields or rooftops, can mitigate these impacts.

In addition to the PV modules themselves, the installation requires supporting infrastructure such as mounting systems, wiring, inverters, and sometimes batteries for energy storage. The production and installation of this infrastructure have their own environmental footprints, including material extraction, manufacturing, and transportation impacts.

Operation and Maintenance

Once installed, PV systems have relatively low environmental impacts during their operational phase. Solar panels generate electricity without direct emissions, noise, or significant water use. However, maintenance activities, such as cleaning the panels, can require water and energy inputs, though these are generally minor compared to the overall lifecycle impacts.

End-of-Life and Recycling

The end-of-life phase of photovoltaic systems poses both challenges and opportunities for environmental sustainability. As PV installations age, increasing volumes of waste PV panels over the next few decades are anticipated. The general lifespan of a PV panel is 30 years, although efficiency losses occur as the PV ages. The International Renewable Energy Agency (IRENA) estimates that 8 million tons of PV panels will reach their end of life and be decommissioned by 2030, growing to 50 million tonnes by 2050. The US National Renewable Energy Laboratory (NREL) also estimates that, at least currently, less than 10% of the US’s decommissioned solar PVs are recycled, not in a small way because in the US it currently costs about US$15–$45 to recycle a silicon PV but only US$1–$5 to dispose of it in landfill.

In addition to the poor use of land, the disposal of PVs to landfill can lead to the release of hazardous materials, such as lead or cadmium, into the environment. While recycling practices for PVs are currently broadly inadequate and underutilised, recycling techniques for PVs can recover valuable materials, reduce the demand for raw material extraction, and mitigate waste management issues (Chowdhury, 2020). However, recycling techniques themselves have potential environmental impacts that should be understood and comparatively assessed.

Lifecycle Assessment and Mitigation Strategies

A comprehensive lifecycle assessment (LCA) of PVs can help quantify and mitigate their environmental impacts across all stages of the supply chain. LCAs consider energy use, greenhouse gas emissions, resource depletion, and other environmental factors from cradle to grave. By conducting an LCA, we can help inform and guide improvements in PV technology and supply chain sustainability, such as increasing energy efficiency in manufacturing, enhancing material recovery through recycling, and developing less hazardous materials and processes.