What is the greenest source of electricity?

Carbon Intensity of ElectricityEarlier this week the new French Prime Minister Manuel Valls reiterated President Hollande’s plan to cut French dependence on atomic power to half of all output by 2025, down from almost 75% currently.  The plan is to curtail nuclear and ramp up renewables.  In his speech he noted that:

The climate is probably the area where regulation is most needed . .  It’s a major challenge for the planet and we will respond with a real low-carbon strategy.

I’m not sure if the context of this quote has gone missing in translation, but I’m guessing that switching from nuclear to renewables is not how France intends to cut its emissions by 40% by 2030. I’m sure it isn’t, because that simply isn’t a mitigation strategy.

In the map above we can see that France already has very low carbon electricity, just 79 g CO2/kWh in terms of carbon dioxide emitted at plants.  This figure is so low precisely because they have so much nuclear.  In fact their carbon productivity of 0.15 kg CO2/$ makes most countries look like climate laggards (the US is 0.4 for example, and China is 2.1).

Reading this story made me wonder how well people understand the carbon intensity of electricity generation.  So here is a quick primer, based on an excellent IPCC meta-study of the issue, looking at full lifecycle emissions of electricity production.

carbon intensity of electricity

It’s basically pretty simple.  Fossil fuels are high carbon sources of electricity while other generation sources are low carbon.

Coal is the most carbon intensive, followed by oil and then natural gas.  Solar PV and geothermal are slightly more carbon intensive than other non-fossil sources, but still very low carbon compared to any fossil fuel.  If you dig into the study you can see the range of data points across different studies for each technology.

So what is the ‘greenest source of electricity’?

If you are looking just at carbon then hydro is a decent bet, closely followed by ocean power, wind and nuclear.  If we could actually make it work biomass with carbon capture and storage (CCS) would be quite something, preferably using the waste from some fast rotation food staple. In the IPCC meta-study biomass with CCS has estimates from -1,368 to -598 g CO2eq/kWh.  Sadly this option looks like it is a very long way from being commercially scalable.

So which do you think is the greenest source of power?  Does your definition of green extend beyond just carbon?

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  • Randy

    One nuclear reactor can power a huge city. I really doubt wind is cleaner than nuclear. It takes a lot of resources to build all those turbines. And in West Virginia, they cut down so many trees to build them.

    • Lindsay Wilson

      Those resources are accounted for in these studies. Wind emissions are pretty much done at construction, nuclear has ongoing mining. Some studies have nuclear up to 200 g/kWh, wind doesn’t make it north of 80.

      • Randy

        There are so many nuclear designs and variables. A thorium reactor doesn’t require fuel mining. Thorium can be extracted from coal, rare earth production, and other industries. Reactors can run on recycled waste or nuclear waste. Sadly, irrational fear means we haven’t really invested in some really promising nuclear technology in the US and many parts of Europe.

        • Lindsay Wilson

          We are going to need a Thorium reactor before we can consider doing an LCA on it

          • Randy

            True. But sadly irrational fear, overregulation, and all the things holding it back mean that may never happen.

            I find it ironic that nuclear, one of the cleanest energy sources we have, the one that has done far more to cut carbon emissions than any alternative energy source, is often attacked by environmentalists.

          • MrL0g1c



            When you’ve lived through the insidious accident that is Chernobyl and listened to decades of lies surrounding the safety of nuclear, you would be right to dislike it.


            No country seems capable of running nuclear power stations without a continuous stream of nuclear accidents continuously poisoning the environment.

            Wind, solar pv, geothermal, hydro, solar-thermal can easily meet the worlds energy needs, why would we want the expensive nightmare that is nuclear power.

          • ivyespalier (Randy)

            Chernobyl was totally the result of stupid decisions by people. Technology is FAR more advanced now than then. Modern nuclear power plants are far, far safer, some reactors designs can’t even experience meltdowns. There will never be a Chernobyl-level disaster again because technology is much better today. Solar and wind is far more advanced than in the 60s and 70s, so is nuclear, why should we compare old technology?

            Nuclear power plants have lower lifetime carbon emissions than wind turbines. Reactors provide clean, cheap power. Nuclear power has saved almost 2 million lives be prevented pollution, look up the NASA study (just google “nuclear has saved 2 million lives”). Nuclear plants have prevented a huge amount of pollution, FAR more than wind and solar has. Countries like Germany and Japan are closing clean nuclear plants and building coal and natural gas plants, thanks to environmentalists and others attacking nuclear. Some plants certainly need decommissioned, but they should be replaced with new reactors. Nuclear should be part of the shift to clean energy, along with wind, geo, and solar.

          • MrL0g1c

            People make stupid decisions, they cut corners, safety systems fail. This won’t change, every year more accidents and leaks happen poisoning ever increasing areas of the planet.

            So if there are safe types of station then why are they still building unsafe types of nuclear power stations that still have the potential to explode (cooling can fail)?

            Hideously expensive:

            Some new wind projects are now producing electricity for as little as 2c to 2.5c per kWh, at that price energy storage can be used in conjunction with wind to meet varying demand better and far cheaper and cleaner and safer than nuclear.


            Nuclear is pointless now, the only thing that will lead to more nuclear stations is cronyism and ignorance.

            If nuclear can save 2 million lives then green can save more with it’s smaller carbon footprint.


            Can you guarantee this won’t happen again?

          • ivyespalier (Randy)

            Nuclear is the safest conventional power source. I am going to bed, I’ll try to look at these links tomorrow. If I forget then you can remind me, if you want…

          • Kevin Kane

            Why would we want to use something that can have an accident, kill people, sicken thousands for years and make large areas of land unusable for thousands of years when we have safer and less environmentally harmful ways to do it ? You do not make sense.

          • http://energyknot.blogspot.co.uk/ William Ashbless

            I have heard “decades of lies surrounding the safety of nuclear” power from the green movement. Despite the 56 or so people killed at Chernobyl I still don’t believe your lies. I’ll take my facts from the UN, WHO, and UNCLEAR who employ scientists to discover actual facts.

          • MrL0g1c

            No international organisation says Chernobyl deaths amount to only 56. The lowest figure is about 4000 and that doesn’t include all deaths. I quote:

            The number is dramatically higher than the estimate of 4,000 deaths presented in a 2005 report by the International Atomic Energy Agency, the World Health Organization, and the United Nations Development Program—a figure that has often been criticized as being far too low and influenced by the
            IAEA’s pro-nuclear agenda.


            The UN’s World Health Organisation and the International Atomic Energy Agency claim that only 56 people have died as a direct result of the radiation released at Chernobyl and that about 4,000 will die from it eventually.

          • Kevin Kane

            Can we put that nuclear reactor one mile upwind from your home ? Ask people downwind that have seen family members die of cancer what they think of nuclear power. There are no lies, we have plenty of evidence both dead and living. This has nothing to do with the “green movement”, that is a green herring.

          • http://energyknot.blogspot.co.uk/ William Ashbless

            Mainly lack of investment is holding back thorium reactors. Greens may fear nuclear power but they don’t influence purse holders. The sad fact – in Britain, TPTB would rather invest in rejigged 60-year old designs like the EPR at Hinkley than put a bent penny into new thorium reactors.

    • MrL0g1c

      A lot of the carbon emissions with wind turbines is due to the concrete used, but that can and should be reduced 80% simply by thinning the concrete by adding other material like rock.

      • ivyespalier (Randy)

        If this is true, why isn’t it done? I would like to see a source backing this up.

        • MrL0g1c

          Me too, can’t find the dam article now :-(

    • MrL0g1c

      What’s worse, cutting down trees or open pit mining?

      Nuclear can power a large city… Wind can power the whole planet.

      Wind and solar have lower carbon footprints:

      • ivyespalier (Randy)

        Thorium reactors can use resources that are already mined and not used. No new mining needed. You have to mine resources and manufacture panels, wind turbines, and other components for RE. No energy source is “GOOD” for the environment and none are impact free, they all impact, and that is why conserving and reducing should be the priority.

        Most of the sources I have seen show nuclear beating solar PV/thermal and it is very close to hydro and wind.

        • MrL0g1c

          2010 National Nuclear Laboratory (NNL) report
          concluded the thorium fuel cycle ‘does not currently have a role to
          play in the UK context [and] is likely to have only a limited role
          internationally for some years ahead’

          So why do the nuclear industry not want to build Thorium reactors?

          The only thing coming close to wind in terms of price is gas.


          ‘Without exception, [thorium reactors] have never been commercially
          viable, nor do any of the intended new designs even remotely seem to be
          viable. Like all nuclear power production they rely on extensive
          taxpayer subsidies; the only difference is that with thorium and other
          breeder reactors these are of an order of magnitude greater, which is
          why no government has ever continued their funding.’


          Meanwhile, regarding the building of a new nuclear plant:

          the EU’s executive arm expressed doubts that British ministers could
          justify state aid to nuclear which it estimated could reach £17bn.
          EC warned of the risk of a “subsidy race” between member states and
          Joaquín Almunia, vice-president for competition policy, described the
          aid package as a complex measure of an unprecedented nature and scale.

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  • MrL0g1c


    … nuclear emits twice as much carbon as solar photovoltaic, at 32 gCO2e/kWh, and six times as much as onshore wind farms, at 10 gCO2e/kWh.

    So, no, nuclear doesn’t have a lower carbon footprint than solar, taking the plant construction, uranium processing and plant decommissioning into account.