Are renewable energies really that clean?

Updated: Sep 25, 2020

The production of electricity is responsible for 35% of the CO2 emissions linked to human activity in the world. Fortunately, renewable energies have experienced a real boom since the 2000s. In the future, these new forms of energy production should account for a greater share of our electricity mix. But is their impact really insignificant?

TLDR: All energy production technologies have a carbon footprint. In some cases, so-called renewable energies are more polluting per kWh than nuclear energy. In all cases, all installations have a significant environmental impact to take into account beyond greenhouse gas emissions.

It is essential to first look at the carbon footprint of each technology. For the purpose of this article, we will use the Life Cycle Assessment . The LCA looks at the environmental impacts of a product over its entire life cycle, which includes the extraction and processing of raw materials, the manufacturing, transport and distribution processes, the use and reuse of the finished product and, finally, recycling and end-of-life waste management.

Fossil Plants

In contrast to renewable energies or nuclear power, electricity generated from fossil fuels (such as coal, gas or oil) generates a lot of greenhouse gas emissions. The LCA of coal-fired power has a carbon balance of 1060g CO2eq/kWh. For gas power, it stands around 730g CO2eq/kWh. And for oil, it reaches 418 CO2eq/kWh. This is equivalent to emitting 85 times more greenhouse gases into the atmosphere than wind electricity, and 19 times more than electricity produced by photovoltaic systems.

Wind Farms

Wind power generation is one of the "greenest" in the electricity mix. Indeed, it does not emit CO2 directly. However, it is important to take into account the carbon balance of its life cycle, which amounts to 12.7g CO2eq/kWh. This rate obviously varies according to the location of the wind farm and the technology used (on or offshore).

Infographics. Wind power, environmental impact. Key figures of wind power. Carbon footprint. Global Warming. Climate Coping.
Hornsdale Wind Farm

Photovoltaic Fields

Photovoltaic is not the least impacting with an emission rate of 55g CO2eq/kWh. There are several reasons for this: land use, rare materials extraction which often consumes a lot of carbon-based energy, and also complex manufacturing processes.


Like wind power, several factors can cause the emission rate of hydropower to vary. These include: installed capacity, the infrastructure required for production, and climatic variations. Nevertheless, hydropower is known to produce low emissions. On average, its emission rate stands around 6g CO2eq/kWh.

Infographics. Global timeline of hydro power plant. Environmental impact of dams. Global Warming. Climate Coping.
Timeline of hydro power, by Energy Watch

Nuclear power

Just like wind power and photovoltaic energy, a nuclear power plant does not emit CO2 during production. The analysis of its life cycle, from the extraction of the raw material to the storage of the waste, shows a carbon balance of 6g CO2eq/kWh, which may seem advantageous. However, it still produces nuclear waste, which is very difficult to recycle and dangerous.

Impact on biodiversity

However, the impacts to be considered go beyond the carbon footprint of renewable energy. These different technologies are often considered to be environmentally friendly, even though they have both positive and negative impacts on biodiversity and ecosystems.

We have summarized below some of the major impacts of each green energy source:

  • Solar energy: habitat loss; bird collisions with facilities; burns to birds exposed to intense solar flux; pollution of water bodies from toxic chemicals used for the treatment of solar panels and soils (herbicides); increased water use (especially in deserts); attraction and disorientation of insects and birds caused by intense or polarized light; disruption of the local micro-climate.

  • Onshore wind energy: collision of birds and bats with wind turbines; internal trauma in bats associated with sudden reductions in air pressure near the blades; disturbance of migratory routes for certain species of birds and bats.

  • Hydraulic energy: disappearance of ecosystems (during dam impoundment); disruption of water flows upstream and downstream of hydroelectric facilities; disturbance of the migratory routes of certain fish species; deterioration in water quality due to changes in sediment loading.

  • Energy from the Seas: environmental disturbances related to the construction of ocean energy facilities; loss or change of habitats associated with the laying of foundations for installations anchored to the sea floor; electromagnetic pollution associated with submarine cables and chemical pollution from lubricants and toxic paints; disruption to the movement and feeding of local and migratory species.

  • Geothermal energy: loss of habitat during conversion of natural areas to geothermal installations; habitat change; emissions of toxic pollutants such as arsenic and boric acid that can defoliate plants or be incorporated by organisms; noise and heat pollution from geothermal installations

Infographics. The footprint of a geothermal project. Impacts on environment of renewable energies. Global Warming. Climate Coping.
National Geothermal Student Competition

The energy transition will not be able to do without the exploitation of renewable energy resources. It is therefore essential to take biodiversity into account for the development of these resources.

In the end, so-called renewable energy production technologies are not harmless to the environment. They are vastly better than fossil fuels, but barely compete with nuclear energy (which has other disadvantages). It is therefore better to focus first on reducing our energy consumption and then replace the remaining consumption with cleaner technologies.

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