Renewables have a carbon footprint dozens of times smaller than fossil fuels despite the initial impact of their construction

The majority of the greenhouse gas (GHG) emissions resulting from renewable energies are produced during the construction phase of wind or photovoltaic farms, hence the widespread notion that it is not worth investing in these technologies to substitute fossil fuels. It is deceptive reasoning, as it only takes the production phase into account rather than the entire life cycle.

In order to compare the environmental impact of different types of energy, you have to take into account the emissions generated over the course of the entire life cycle of the farms that produce it, from the extraction of raw materials needed to manufacture the technology to its dismantling and waste management. Fossil fuel energies (petroleum, carbon and gas) have a carbon footprint ranging between 469 and 1,001 grams of CO2 eq/kWh. In comparison, wind energy’s carbon footprint is approximately 16 grams of CO2 eq/kWh, hydraulic energy’s is between 4 and 14 grams of CO2 eq/kWh and solar energy’s is between 30 and 80 CO2 eq/kWh. Wind, hydraulic and solar energies are the three main types of renewable energies in Spain, according to the same IPCC analysis, which expresses the data in CO2 equivalent per kilowatt hour (CO2 eq/kWh).

The largest amount of renewable energy produced in Spain comes from wind (21.8%), water (12.2%) and the sun (6.1%), but the life-cycle assessment of different types of energy production “depends greatly on the sources you take”, Alicia Valero, coordinator of the Industrial Ecology research group of the CIRCE Institute, explains to Verificat.

Comparing emissions

Renewables have, on average, a carbon footprint that is between 10.9 and 250.25 times smaller than non-renewables if we compare the figures provided in the report by the Intergovernmental Panel on Climate Change (IPCC). This estimation can vary over the years and also over the course of the life cycle, because the technologies analysed evolve just as the tools and raw materials do. For example, in the case of wind energy, the IPCC report indicates that it has a carbon footprint ranging from 14.4 to 18.4 grams of CO2 eq/kWh for onshore and offshore sites, figures that are higher than hydraulic energy’s carbon footprint, which ranges between 4 and 14 grams of CO2 eq/kWh.

However, ten years after the publication of this report, the figure might be outdated. For example, experts note today that wind energy has the lowest carbon footprint, as indicated in this report from 2019 and this one from 2014. The environmental impact of solar panels is concentrated in their manufacturing phase, a process that uses materials such as silicon, cadmium and germanium, whose production requires both mining and purification processes that use materials hazardous to human and environmental health. Aspects such as each panel’s capacity to convert energy – ranging from 3 to 15%, depending on the model – as well as its lifespan – between 15 and 30 years – can also affect the total amount of greenhouse gas emissions, as indicated in this report. Precisely because of this, greenhouse gas estimates can vary greatly depending on the type of solar panel, ranging between 30 and 80 grams of CO2 eq/kwh, according to the IPCC analysis. As a result, among the renewable electricity generation technologies, it is the energy that produces the most GHG emissions.

The data in context

Pedro Fresco Torralba, director general of the Energy Transition of Valencia, insists to Verificat that the greatest portion of carbon emissions generated by renewable energies comes from construction, while the opposite is true for thermal power plants, as those emissions are generated after they are built.

In fact, a review on the topic published in 2019 insists on this point, noting that “in the case of renewable energies, the infrastructure is the phase of the life cycle that contributes most heavily to total GHG emissions, with a contribution of up to 99%, whereas for non-renewable technologies it is the phase of operation that contributes most, with a contribution ranging from 80% to 90%”.