The CO₂ footprint of different energy sources

Footprinting & LCA

Our economy runs on energy.

Economic growth is strongly linked to energy usage – unfortunately. At the same time, the energy sector is the biggest contributor to global CO₂ emissions (if we consider only direct emissions – after all, most of the energy is used by other sectors. That’s why it’s important to understand your Scope 1,2 and 3 footprint).

But what’s the environmental impact of all that energy?

We hear it all the time:

“Solar isn’t actually more sustainable, when you look at the production of the panels.”

“Wind mills don’t produce the electricity they need to be manufactured.”

Luckily, we don’t have to rely on hearsay to understand if these statements are actually true.

The IPCC (Intergovernmental Panel on Climate Change) has published many reports on this topic. But these reports can be rather long and technical, so we wanted to share the insights with you in a more visible fashion. You can read the full data (published in 2014) here.

Which energy sources do we look at?

For this article, we’ll be looking at large-scale energy sources. We will not look at Diesel, Fuel or other energy sources that are used for peak electricity or transportation.

Some of the energy sources are named in multiple instances – wind energy can be on- or offshore. Solar energy can either come from rooftops on small-scale, on a large utility scale, or in concentrated areas (e.g. using mirrors to concentrate sunlight in large areas). Biomass can be used as 100% main energy source, or co-fire in a coal plant at only 10% share.

What unit do you measure energy in?

The emissions of the different energy sources are measured in grams of CO₂-equivalent per kWh. One kWh is enough for using a 1000 Watt hairdryer for one hour or 70 cups of coffee from a coffee machine. Of course, it also depends on the energy efficiency of your devices. ?

The data depicted in this article is the impact averaged out throughout the life cycle of the energy source. You can learn more about the methodology of Life Cycle Assessments (LCA) in our Beginner’s Guide to LCA (available in German, Dutch and English).

Coal, Biomass & Gas: The dirty energy sources

I knew that the difference in impact between renewables and fossil fuels was big. But THAT big? Based on median numbers, the impact of one kWh of energy from coal is more than 80x that of onshore wind energy. And biomass isn’t necessarily better, either.

The difference is so big that I had to zoom into the graph to get more insights into the performance of more sustainable energy sources…

Environmental Impact of Different Energy Sources per kWh
Environmental Impact of Different Energy Sources per kWh

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The low end of the scale: Which source of energy has the lower CO₂ footprint?

It’s not surprising that renewable energies have a lower CO₂ footprint than fossil fuels. But how do they compare to each other? The answer: It depends. Of course, the environmental impact of wind, solar and hydro also depends on the environment they are being used in. Unsurprisingly, the minimum impact varies quite substantially.

Should we ignore that nuclear energy is, based on median data, the winner of this comparison? It’s no secret that the CO₂ footprint of nuclear energy is very low, and this has never been the argument against nuclear energy. Of course, there are many other factors to consider – and we will not dive into this debate at this point. ?

Environmental Impact of Different Energy Sources per kWh
Environmental Impact of Different Energy Sources per kWh

This is the full data breakdown, that can also be found in the IPCC report.

gCO2 per kWh per energy source. Source

Min Median Max
Wind onshore 7 11 56
Nuclear 3,7 12 110
Wind offshore 8 12 35
Hydropower 1 24 2200
Concentrated Solar  8,8 27 63
Geothermal 6 38 79
Solar PV—rooftop 26 41 60
Solar PV—utility 18 48 180
Biomass—dedicated n 130 230 420
Gas 410 490 650
Biomass—cofiring n. 620 740 890
Coal 740 820 910
Zazala Quist

Hi, I'm Zazala - former content writer at Ecochain. My goal: make difficult sustainability concepts - understandable to all.

All posts by Zazala