Lever 1: prioritizing low-carbon materials by implementing eco-design approaches
The majority of CO2 emissions linked to renewable energy can be attributed to the materials used: hydroelectric stations use large amounts of concrete, solar panels use silicon, glass, plastic, copper and silver, and wind turbines use primarily steel, concrete, and composites. Extracting and manufacturing these materials emits large amounts of CO2.
It is possible to reduce these emissions by prioritizing lower-emitting materials, by following eco-design practices that reduce the amounts of material necessary, or by sourcing from suppliers who propose low-carbon materials thanks to sustainable formulations and using low-carbon energy mixes to power their production processes. For example, low-carbon steel and concrete emit up to 10- and 2-times less CO2 than their traditional counterparts, respectively – all while having the same mechanical properties. However, the current cost of these materials is still a barrier in their usage, as it could strongly compromise the profitability of certain projects.
As a key example, around 75% of the carbon impact of wind turbines is due to the extraction and transformation of their building materials (mainly concrete and steel). Depending on the type of wind turbines, these extraction-related emissions comprise on average between 10-15 gCO2/kWh. Moving towards low-carbon alternatives could enable, in theory, half of the impact of such materials to be reduced.
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Lever 2: reducing the impact of green energy infrastructures on biodiversity
Making a renewable energy even greener is not limited to reducing its carbon footprint! It is also necessary to account for all of the other environmental impacts of these installations including biodiversity, forests, freshwater, ocean acidification, nitrogen and phosphate cycles, chemical pollution, aerosol emissions in the atmosphere, etc.
For example, hydroelectric projects change the natural paths of water flow, resulting in loss of terrestrial and aquatic habitats. They can also act as barriers that perturb fish migration. Upstream of these projects, thought should be given to choosing a location that minimizes impact on sensitive ecosystems and threatened species. Structures should be put in place that allow fish to migrate upstream and downstream of hydroelectric plants, and new ecosystems should be created in areas that are impacted by their construction.
Renewable energy can have numerous other potential harmful effects on biodiversity. For example, birds and bats can have collisions with wind turbines, especially during migration seasons. The large amount of water needed for hydrogen production can diminish this essential resource, and as such affect local ecosystems. Burying used solar panels that contain lead or cadmium can lead to soil pollution. Seismic risks provoked by injecting water into the earth’s crust for extracting thermal energy can lead to soil instability and landslides that negatively impact local biodiversity.
Lever 3: optimizing installation, maintenance and deconstruction operations
Installation, maintenance and deconstruction operations also contribute to a non-negligible part of the emissions of renewable energies.
To reduce emissions during installation, it is necessary to optimize the routing of materials and equipment, to prioritize places with a low-carbon energy mix during the production and assembly stages, and to optimize the installation process.
For example, in the case of offshore wind turbines installed in the open sea using large ships that emit significant CO2, it is necessary to encourage the usage of cleaner ships, and to optimize the installation steps in order to reduce the time during which the ships are used. One example of such optimization is the on-shore assembly of turbines in the port before bringing them to the installation site at sea, which is being considered by players like Seawind. The CO2 emissions that could be avoided by implementing such measures are difficult to calculate, but could be on the order of 2g of CO2 per additional kWh.
Reducing emissions linked to maintenance operations often consists of limiting the movement of operators that use polluting forms of transport, whether it’s by ground, air or sea. Pushing for digitization, predictive maintenance, and remote inspections (for example by drone) can reduce the impact of maintenance on the carbon footprint of the installation.
Finally, as is the case with installation, the deconstruction must be optimized in order to avoid unnecessary trips and to consume the least energy possible.
Lever 4: prolonging the longevity of equipment
Increasing the usage rate and lifespan of different means of renewable energy production is also a simple way to reduce their carbon footprint. If, for the same amount of CO2 emitted during the extraction of materials, installation and deconstruction, more electricity could be generated over a longer period of time, this would obviously positively impact the CO2 emissions per quantity of energy produced.
Increasing the usage rate of a solar panel by 15% and its lifespan by 5 years can diminish emissions by 30%, or roughly 14g of CO2 per kWh.
Lever 5: recycling the materials of the infrastructures at the end of their life cycles
Recycling materials is another possible lever, due to its impact on the global carbon footprint of equipment and installations. However, while materials like steel or copper are currently recyclable without losing their mechanical, electric or physical properties, other recycled materials suffer from loss of performance when re-used for their original application. This is notably the case for concrete from deconstruction, for which recycling impacts their physico-chemical properties and reduces their mechanical resistance. Similarly, thermoset composites are difficult to recycle and cannot be reused for structural purposes. Their replacement by recyclable thermoplastics could change this, but these new composites are still in the developmental stage.
In the case of solar panels, for whom more than 90% of their mass (glass, plastics and aluminum) can be recycled, implementing recycling steps could reduce 30-50% of CO2 emissions all along their life cycle, amounting to 14-23g of CO2 per kWh.
While it is theoretically possible to reduce the carbon footprint of materials and different operating phases of energy production infrastructures, the solutions that enable this often encompass extra costs or the implementation of insufficiently developed alternatives. Additionally, making green energy even greener will require limiting the environmental impacts beyond carbon emissions, and there are still numerous problems to solve to avoid other kinds of pollution and preserve biodiversity and natural resources.
We are confident that innovation will remove these technological and economic barriers in the coming years. Our team is here to explore decarbonization opportunities with you! Don’t hesitate to contact our team!
 Alcimed’s estimates
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About the author,
Sébastien, Senior consultant in the Alcimed’s Energy Environment Mobility team in France