What is the greenest source of electricity?

by Lindsay Wilson in Discussion,Housing

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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