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CO2 balance: renewable energies vs. fossil fuels
10/21/24Reading time:
Renewable energies such as wind power, solar energy and hydropower are often seen as the environmentally friendly solution in the fight against climate change. Even if they cause hardly any emissions during operation, CO2 emissions should be considered over the entire life cycle. Emissions also occur in the so-called upstream chain - i.e. during production, transportation, installation and maintenance - but these are much lower compared to fossil fuels such as coal, oil or gas. This article provides a detailed comparison of the carbon footprint of renewable energies and fossil fuels and illustrates why it is essential to switch to sustainable energy sources despite upstream chain emissions.
Emissions from fossil fuels
Fossil fuels such as coal, oil and gas have dominated global energy production for decades, but are also the main sources of CO₂ emissions. These are generated not only during combustion, but throughout the entire life cycle:
- Extraction: considerable amounts of CO₂ and methane are already released during the extraction of coal, oil and gas. Methane, which is produced during natural gas extraction and has a far greater impact on the climate than CO₂, is particularly problematic.
- Transportation: Fossil fuels often have to be transported over long distances, which also contributes to CO₂ emissions, for example through the use of ships, pipelines or trucks.
- Combustion: The majority of emissions are caused by burning fossil fuels to generate electricity. Coal-fired power plants emit around 820 g of CO₂ per kWh, while natural gas emits around 450 g of CO₂ per kWh.
In total, fossil fuel power plants cause between 900 and 1,200 g of CO₂ equivalents per kilowatt hour (kWh) generated.
Emissions from renewable energies
Renewable energies such as wind power, solar energy and hydropower are much more environmentally friendly, but also cause emissions that mainly occur in the upstream chain. However, these are significantly lower compared to fossil fuels:
- Production and construction: the production of wind turbines, solar plants and hydropower plants requires raw materials such as steel, concrete and silicon, which leads to CO₂ emissions.
- Transportation and installation: The delivery of the systems and their installation cause additional emissions through the use of machinery and vehicles.
- Maintenance and dismantling: Even if operation is virtually emission-free, small amounts of CO₂ are generated during maintenance and subsequent dismantling.
Over the entire life cycle, however, emissions from renewable energies are very low:
- Onshore wind power: 12 to 15 g CO2/kWh
- Wind power at sea: 5 to 12 g CO2/kWh
- Solar energy: 20 to 50 g CO2/kWh
- Hydropower: 1 to 30 g CO2/kWh
