IN SUMMARY
Where the carbon hides in solar panel manufacturing
Where the carbon hides in solar panel manufacturing
Solar PV is one of the clearest wins in decarbonisation, producing on average 20 times fewer emissions than coal power and generating 20 to 30 times more energy over its life than goes into making it. But manufacturing solar modules is energy- and material-intensive, and that embodied footprint is coming under regulatory scrutiny. Minviro assessed the product carbon footprint of a monocrystalline silicon module, from silica extraction to finished panel, to show which stages matter most and how much supply chain choices change the result.
Solar PV is one of the clearest wins in decarbonisation, producing on average 20 times fewer emissions than coal power and generating 20 to 30 times more energy over its life than goes into making it. But manufacturing solar modules is energy- and material-intensive, and that embodied footprint is coming under regulatory scrutiny. Minviro assessed the product carbon footprint of a monocrystalline silicon module, from silica extraction to finished panel, to show which stages matter most and how much supply chain choices change the result.
Solar PV is one of the clearest wins in decarbonisation, producing on average 20 times fewer emissions than coal power and generating 20 to 30 times more energy over its life than goes into making it. But manufacturing solar modules is energy- and material-intensive, and that embodied footprint is coming under regulatory scrutiny. Minviro assessed the product carbon footprint of a monocrystalline silicon module, from silica extraction to finished panel, to show which stages matter most and how much supply chain choices change the result.
The footprint is large and variable. A standard mono-Si module carries between 145 and 420 kg CO₂e per m², and the total varies by around 60% between the highest and lowest-impact supply chain scenarios studied.
The footprint is large and variable. A standard mono-Si module carries between 145 and 420 kg CO₂e per m², and the total varies by around 60% between the highest and lowest-impact supply chain scenarios studied.
The footprint is large and variable. A standard mono-Si module carries between 145 and 420 kg CO₂e per m², and the total varies by around 60% between the highest and lowest-impact supply chain scenarios studied.
Silicon is the hotspot. Solar-grade silicon and monocrystalline crystal production contribute most of the carbon footprint, driven by the energy needed to purify silicon to 99.9999999%.
Silicon is the hotspot. Solar-grade silicon and monocrystalline crystal production contribute most of the carbon footprint, driven by the energy needed to purify silicon to 99.9999999%.
Silicon is the hotspot. Solar-grade silicon and monocrystalline crystal production contribute most of the carbon footprint, driven by the energy needed to purify silicon to 99.9999999%.
Electricity decides the outcome. Because coal generates more than 60% of the electricity used in PV manufacturing today, the grid mix used across the five production stages is the single biggest lever on the final footprint.
Electricity decides the outcome. Because coal generates more than 60% of the electricity used in PV manufacturing today, the grid mix used across the five production stages is the single biggest lever on the final footprint.
Electricity decides the outcome. Because coal generates more than 60% of the electricity used in PV manufacturing today, the grid mix used across the five production stages is the single biggest lever on the final footprint.
Why solar's manufacturing footprint matters
Solar PV is set to triple in capacity between 2022 and 2027, overtaking hydropower, gas and eventually coal in the global generation mix. Its in-use case is unambiguous: a module’s lifetime carbon footprint is around 20 times lower than coal power, and it generates far more renewable energy than the fossil energy used to make it. But that does not make manufacturing burden-free. The energy, metals and chemicals used to build a panel carry embodied carbon that cannot be ignored as the industry scales, especially as regulators move toward maximum carbon footprint limits, ecodesign criteria and digital product passports. Crystalline silicon dominates the market, with mono-Si accounting for over 80% of annual solar generation, which is why this study focused there.
Solar PV is set to triple in capacity between 2022 and 2027, overtaking hydropower, gas and eventually coal in the global generation mix. Its in-use case is unambiguous: a module’s lifetime carbon footprint is around 20 times lower than coal power, and it generates far more renewable energy than the fossil energy used to make it. But that does not make manufacturing burden-free. The energy, metals and chemicals used to build a panel carry embodied carbon that cannot be ignored as the industry scales, especially as regulators move toward maximum carbon footprint limits, ecodesign criteria and digital product passports. Crystalline silicon dominates the market, with mono-Si accounting for over 80% of annual solar generation, which is why this study focused there.
How the study was built
Minviro ran a cradle-to-gate LCA with a functional unit of one square metre of mono-Si module, specified with 170 µm wafers and 19.5% conversion efficiency, ending at the factory gate. Background data combined Ecoinvent 3.9.1 with Minviro’s proprietary raw material data points, particularly for high-purity silicon, using the Environmental Footprint 3.1 method and focused on climate change potential. The base model uses global average production, then refines to regional examples. To test variability, the team modelled metallurgical-grade silicon from five geographic sources and three regional electricity grid mixes across the five manufacturing stages: solar-grade silicon, monocrystalline crystal, wafer, cell and module.
Minviro ran a cradle-to-gate LCA with a functional unit of one square metre of mono-Si module, specified with 170 µm wafers and 19.5% conversion efficiency, ending at the factory gate. Background data combined Ecoinvent 3.9.1 with Minviro’s proprietary raw material data points, particularly for high-purity silicon, using the Environmental Footprint 3.1 method and focused on climate change potential. The base model uses global average production, then refines to regional examples. To test variability, the team modelled metallurgical-grade silicon from five geographic sources and three regional electricity grid mixes across the five manufacturing stages: solar-grade silicon, monocrystalline crystal, wafer, cell and module.
What the results show
The finished module footprint ranges from 145 to 420 kg CO₂e per m², a span of around 60% driven by supply chain choices. The first two stages dominate. In solar-grade silicon production, over half the impact comes from electricity, with the rest from heat and the embodied metallurgical-grade silicon feedstock. In crystal production via the Czochralski process, electricity and solar-grade silicon are the largest contributors. For the wafer, cell and module stages, the embodied impact of the silicon components carried forward outweighs everything else, which points firmly back to those first two stages as the targets for reduction. Interestingly, switching the metallurgical-grade silicon source alone changes the final footprint by only around 5%, because the energy intensity of purification and crystallisation dwarfs the feedstock’s own footprint. Per kilogram, metallurgical, solar-grade and single-crystal silicon need roughly 10 to 20, 40 to 200, and 120 to 300 kWh respectively. The real lever is how cleanly that purification energy is supplied.
The finished module footprint ranges from 145 to 420 kg CO₂e per m², a span of around 60% driven by supply chain choices. The first two stages dominate. In solar-grade silicon production, over half the impact comes from electricity, with the rest from heat and the embodied metallurgical-grade silicon feedstock. In crystal production via the Czochralski process, electricity and solar-grade silicon are the largest contributors. For the wafer, cell and module stages, the embodied impact of the silicon components carried forward outweighs everything else, which points firmly back to those first two stages as the targets for reduction. Interestingly, switching the metallurgical-grade silicon source alone changes the final footprint by only around 5%, because the energy intensity of purification and crystallisation dwarfs the feedstock’s own footprint. Per kilogram, metallurgical, solar-grade and single-crystal silicon need roughly 10 to 20, 40 to 200, and 120 to 300 kWh respectively. The real lever is how cleanly that purification energy is supplied.
What it means for solar manufacturers
The practical message is that low-impact factory operations alone will not make a low-carbon panel; manufacturers must source low-impact silicon and, above all, power purification and crystallisation with clean electricity. With production heavily concentrated in China, often on coal-heavy grids, this creates a clear opening: European and US manufacturers can compete on carbon intensity even at higher cost, as regulation increasingly rewards lower-footprint products. Beyond silicon and energy, the moderate contributors such as aluminium, glass, metallisation paste and chemicals can each be addressed in turn as part of a reduction roadmap. Manufacturers also need to plan for end-of-life, since recycling remains costly and immature, and reducing production impact only to send modules to landfill simply shifts the burden. Systematic collection could eventually meet over 20% of the industry’s demand for aluminium, copper, glass and silicon, and nearly 70% of its silver, between 2040 and 2050.
The practical message is that low-impact factory operations alone will not make a low-carbon panel; manufacturers must source low-impact silicon and, above all, power purification and crystallisation with clean electricity. With production heavily concentrated in China, often on coal-heavy grids, this creates a clear opening: European and US manufacturers can compete on carbon intensity even at higher cost, as regulation increasingly rewards lower-footprint products. Beyond silicon and energy, the moderate contributors such as aluminium, glass, metallisation paste and chemicals can each be addressed in turn as part of a reduction roadmap. Manufacturers also need to plan for end-of-life, since recycling remains costly and immature, and reducing production impact only to send modules to landfill simply shifts the burden. Systematic collection could eventually meet over 20% of the industry’s demand for aluminium, copper, glass and silicon, and nearly 70% of its silver, between 2040 and 2050.