CO2 balance: renewable energies vs. fossil fuels

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 are also produced 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 the switch to sustainable energy sources is essential despite upstream chain emissions.

Fossil fuel emissions

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 produced 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 produce 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 panels and hydroelectric power 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 produced 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

Conclusion

Despite their upstream emissions, renewable energies have a significant advantage over fossil fuels. While fossil fuels cause high CO2 emissions throughout their entire life cycle, the emissions from renewable energies are limited to the initial phase of production in particular. The carbon footprint of renewable energies is clearly more positive compared to fossil fuels, which makes the switch to sustainable energies essential in order to achieve global climate targets.