Greenpeace and Arithmetic

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Greenpeace and other environmental groups have recently expended a great deal of energy trying to get the UK to commit to de-carbonizing the UK electricity grid by 2030. This hoped for target was for, on average, 50 g CO2 to be produced per kWh of electricity, which the government has decided to not include in its energy bill.

Instead of going over the debate over whether a target is a good idea, let’s instead consider whether the government would be wise to follow Greenpeace’s overall policy prescriptions. I’ll simplify these to three policies: the UK has a legally binding target of 50 gCO2 /kWh for electricity, no nuclear power plants, and no CCS power plants by 2030. So, how do we get to 50 g CO2/kWh in such a scenario?

In simple mathematical terms the carbon intensity of electricity generation is the sum of carbon intensity of each source multiplied by the percentage of electricity coming from that source.

Here are estimates of the carbon intensity of electricity from fossil fuels:

fossil fuels

Greenpeace obviously don’t want Coal or CCS on the grid. So, we’ll just have to assume that the grid has gas for back up. We’ll consider later how much is allowed. Below is the carbon intensity of low carbon electricity sources.

low carbon

Let’s begin by assuming that the renewable energy in the grid has zero emissions. In this case reaching our target would require at most 13% of power to come from gas. 87% renewables seems quite ambitious.

This however assumes that we ignore the full life cycle emissions of renewables. Let’s say our de-carbonisation target is for 50 g CO2/kWh over the full life cycle of plants.  Wind power has the lowest footprint, so let’s use this to get a lower bound on the amount of gas allowed. The exact figure for wind’s carbon intensity is dependent on wind farm locations, and the relative onshore/offshore mix. However a figure of 15 g CO2/ kWh appears to be a reasonable assumption to make. This then would push us up to  91% renewables to meet our target.

There are other factors to consider, however it appears reasonable to conclude that the only way to reach 50 g CO2 /kWh is to get something like 90% of electricity from renewables. The reasons for thinking this is not feasible have been well laid out by David MacKay and others, and I will not go over them here. However, instead of countering these arguments, and demonstrating how we can de-carbonize electricity without nuclear or CCS, Greenpeace appears to have settled on a rather convenient response: “we don’t like scenarios.” This is an argument that lacks seriousness.

Greenpeace propose that we act like a plumber who has thrown away some of his tools before he arrives for a job, without first checking if his remaining tools are adequate. This of course is foolish behaviour, and it is time we recognised it for what it is.


2 thoughts on “Greenpeace and Arithmetic

    Alexander Harvey said:
    January 13, 2013 at 2:42 am

    I don’t yet see any legal significacnce to the year 2030, nor to any figure for gco2/kwh for power generation.

    The fourth budget will run to 2027, the next from 2028-2032.

    It is true that some level for the gco2/kwh is implied but only after the emission splits have been determined and the generation requirement has been settled.

    Was there any serious suggestion that the government were going to make such a commitment ?


    MarcoMC said:
    January 29, 2013 at 8:29 pm

    It’s very easy to argue for any case when you cherry pick data and act as though it is the one and only answer.

    The reality is that CO2 / kWh for nukes goes above 100 grams in many studies. But it is impossible to know exactly how much the nuke lifecycle emits because no one knows where the waste is going. We can be certain it is higher than the unsourced graph offered here.

    And if a nuke catastrophically failed in the UK the CO2 and economic cost would be massive.

    The other failure in this ‘analysis’ is ignoring the fact that nukes are not economically viable. The evidence and expert opinion for that is massive.

    Given these facts it is clear that this blog is not offering serious analysis or commentary.

    P.S. David MacKay’s book has been discredited by many energy experts, and it is now long out of date.


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