The last post which I published about this subject mainly dealt with energy output and costs associated with wind and nuclear power. The other major side of the equation is the carbon footprint of the various technologies. The carbon pumped into the atmosphere and absorbed into the oceans is having a direct and significant impact on every person on the planet, with the poorest people suffering huge economic and physical hardships.
There are many sources of data on both the operating and life-cycle footprints, but i’ve found a few which show the relative differences in different ways.
The first is from the parliamentary Office of Science and Technology…
carbon footprint of electricity generation – oct 2006 (POST)
This deals with the operating carbon footprint of the various technologies. It shows that nuclear has the lowest operating carbon footprint, at only 5 grams per KWh, compared with just over 5 grams for wind, or 1,000 grams for coal.
The thing that really pushes nuclear up (to around 85 grams per KWh) is the pre and post energy production stages, including mining of the uranium ores, enrichment and fuel fabrication. 35% of the total is made up of decommissioning the power plant and constructing and maintaining the waste stroage facilities.
A good ‘answers’ article has a good summary of the comparitive figures…
‘Early studies of the carbon footprint of nuclear power seem not to have included the construction, decommissioning, and waste disposal, which are always included in a total carbon footprint. Waste disposal is a particularly difficult area to deal with because no one know how it will be done, so no one knows what figures to use for carbon footprints.
So estimates from studies dated 1998 to 2003 at the carbon footprint were all in the range of 11-13 grams of CO2 equivalent per kilowatt hour (g. CO2e/kWh). Four studies in 2004 and 2005, two of which agreed with the earlier estimates, produced an average figure of 43.5 CO2e/kWh. Five studies in 2006 produced an average of 84 CO2e/kWh. And three studies in 2007 produced an average of 93 g. CO2e/kWh for nuclear power.
Since the earlier studies were clearly not addressing the total carbon footprint, and the later ones were, we can probably use a figure of 85 g. CO2e/kWh. An article by Benjamin Sovacool arrives at 65 g. CO2e/kWh, averaging the early and late numbers, but the earlier numbers are clearly wrong, despite the fact that they are much quoted. To put this into context, the following are average estimates of total greenhouse gasses by production type with numbers of grams of CO2e/kWh:
1000 – coal
900 – oil
750 – open cycle natural gas
580 – closed cycle natural gas (closed cycle natural gas combined with co-generation might bring this down to 400 g. CO2e/kWh)
500 – coal plant burning 50% coal with 50% miscanthus
110 – old solar photovoltaics
95 – biomass from miscanthus
85 – nuclear
40 – concentrated solar thermal with thermal storage
35 – new solar photovoltaics
25 – biomass from gasification of wood chips (used to fuel conventional natural gas turbines)
21 – wind
15 – hydroelectricity
<10 – geothermal doublet
These numbers come mostly from the Wikipedia article cited below. The figure for nuclear is extracted from the Sovacool article cited by using only studies dated after 2004. The figures for solar come from current solar literature as solar technology has changed a lot in the last ten years. The figures for biomass come from the UK Parliamentary Office of Science and Technology. This places the carbon footprint of nuclear as 400% to 1600% of wind, hydro, solar, but about 15% of natural gas, and 8.5% of coal. Bear in mind that some estimates for the nuclear are much higher.’ http://wiki.answers.com/Q/What_is_the_carbon_footprint_of_nuclear_energy#ixzz1NMp2O6Nb
Another article from Nature Reports Climate Change…
Nature reports climate change – nuclear energy (Sept 24 2008)
So, nuclear is pretty clearly better than any of the fossil fuel technologies. The Uranium mining and quality issue is important and relying on what are finite resources isn’t a good idea. However, the POST report has the following conclusion:
‘Some analysts are concerned that the future carbon footprint of nuclear power could increase if lower grade uranium ore is used, as it would require more energy to extract and refine to a level usable in a nuclear reactor. However, a 2006 study by AEA Technology calculated that for ore grades as low as 0.03%, additional emissions would only amount to 1.8gCO2eq/kWh. This would raise the current footprint of UK nuclear power stations from 5 to 6.8gCO2 eq/kWh (Fig 3). If lower grades of uranium are used in the future the footprint of nuclear will increase, but only to a level comparable with other ‘low carbon’ technologies and will not be as large as the footprints of fossil fuelled systems.’ (POST – carbon footprint of electricity generation)
Recycling and reprocessing existing waste will provide some releif, but still only part of the answer. The waste storage question for me is the single biggest problem. Reprocessing seems to be the answer, but will come with a cost. This seems a better solution than 100,000 years of bedrock storage, which just hides the problem and doesn’t deal with it.
Both forms of nuclear power, fission and fusion, have an important property: the nuclear energy available per atom is roughly one million times bigger than the chemical energy per atom of typical fuels. This means that the amounts of fuel and waste that must be dealt with at a nuclear reactor can be up to one million times smaller than the amounts of fuel and waste at an equivalent fossil-fuel power station.(http://www.inference.phy.cam.ac.uk/withouthotair/c24/page_161.shtml)
Time-scales are often cited as another reason that nuclear power stations shouldn’t be built. Well, taking an average of 10 years for a nuclear power station, this is equal to the estimated time taken from start to finish for the Thames Estuary wind farm project (not yet completed). If you want very large amounts of electricity to be generated, it takes time to provide the systems.
France added 48GW of nuclear capacity – equivalent to more than half of our entire electricity system – in just 10 years. (Committee onClimate Change)
Base load is also often talked about. Nuclear provides this non-stop background energy, 24 hrs a day, 365 days a year. Solar and wind do not. These renewable systems have to be supported by non-renewable systems, often based on fossil-fuel technology. The large wind farms operate at around 70% and there has to be major energy production means for the other times.
The latest George Monbiot blog makes some interesting points. He questions why we are looking at the energy issue in terms of either renewables OR nuclear, instead of both together. He cites the Committee on Climate Change recommendations. The CCC is an independent body which advises the UK government on setting and meeting carbon budgets and on preparing for the impacts of climate change.
The Committee on Climate Change recommends an energy mix of 40% Nuclear, 40% renewables, 15% carbon capture and storage and up to 10% gas without carbon capture.
In terms of the issue of supply of uranium for nuclear power…
“Although there is a finite supply of uranium available, this will not be a limiting factor for investment in nuclear capacity for the next 50 years.”
What’s the answer? Well, I believe that nuclear power has vast potential to fill the 30 to 40 year gap from now until the time when renewables are realistically able to take up the very significant energy demand. Renewables just aren’t ready yet and cannot provide guaranteed power supplies. The solar PV panels on my roof are great, but only supply 50% of our electricity and not much at all during the winter months.
I also believe de-centralised power systems are the way forward, given the inefficiencies of the national grid (8% of total energy lost through heat from cables and transformers). Utilising locally produced energy, from renewable sources is the logical approach.
What will certainly be part of the solution up to the point renewables take over is an increasing emphasis on energy saving measures and renewable projects. You can’t just jump from our fossil-fuel dependent world to a clean and sustainable world overnight. It’s this bridge which is the real issue. No-one thinks renewables can’t offer a long-term energy solution, it’s just the process of moving from fossil-fuels to renewables which will be the real challenge. This won’t be a quick process and it won’t be without serious conflicts.
“Saving civilization is not a spectator sport.” Lester R. Brown (President, Earth Policy Institute): time for plan B