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I told Turambar that there are other numbers than those; I didn't have much time for searching, here is just one, which isn't that different -- the GEMIS numbers by the Öko-Institut:

Specific lifecycle CO2 emissions in g/kWh = t/GWh:

Subbituminous coal power plant: 1153
Bituminous coal power plant with imported coal: 949
Subbituminous coal heating plant: 729
Bituminous coal heating plant with imported coal: 622
Natural gas combined cycle power plant: 428
Natural gas combined cycle heating plant: 148
Nuclear power plant (uranium imported only from South Africa), without spent fuel storage: 126
Multicristalline solar cell (with current energy supply for manufacturing): 101
Natural gas block heating power plant: 49
Hydroelectric power: 40
Nuclear power plant (present resource use in Germany), without spent fuel storage: 32
Solar electricity import from Spain: 27
On-shore wind: 24
Off-shore wind: 23
Biogas block heating power plant: -409[Typo?]

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Jul 14th, 2007 at 12:42:56 PM EST
[ Parent ]

No, not a typo.

That's an actual number coming out from a completely fucked-up model meant to give the desired numbers, in that case, extol the virtues of heat/power cogeneration, using an argument I just cannot understand. Makes no fucking sense. See the explanatory paper

When comparing electricity-only options like nuclear, wind etc. with combined heat and power (CHP) generation (i.e. cogeneration), one must deal with the additional non-electric - but still useful - heat output supplied by the cogeneration system. To do so, first the total CO2 emissions of the cogeneration system (i.e. the emissions from generating both electricity and heat) are determined. Then, the emissions of a heating system delivering the same amount of heat are subtracted ("credited"), because the cogeneration system not only generates electricity, but also replaces heat supply from another system - say, an oil heater - and, hence, replaces also its emissions.

For example, the production of 1 kWh of electricity in a gas-fired internal combustion engine (ICE) cogenerator substitutes about 2 kWh of heat which does not have to be produced separately. The CO2 emissions thus saved are credited to the cogeneration system.

How do they compute that credit for the heat? Compared to burning coal to generate the same heat?

If they want to compared on a CHP basis, they need to compare the total output of a biomass cogeneration to the output other sources would require in electricity to also generate that heat. It will probably make the biomass cogen look extra double plus good but, fuck, going negative on CO2 emission is an amazing "methodology". Nothing is CO2 negative unless it collects CO2 in the atmosphere and buries it in the ground. Nice way to spin numbers. This is gold-plated bullshit of the first order.

For what it's worth (no details either), a UK parliamentary report gives nuclear at parity with wind.

About the figure for nuclear power, as the Öko-Institut doesn't give the break-down in the explanatory paper, I would assume it's the same joke as the very entertaining Wise Uranium numbers which, for enrichment, assume both the most energy-expensive enrichment process (gaseous diffusion) and the worst way of supplying that energy (low efficiency coal plant).

The coal assumption has a veneer of validity for the USEC plant in Paducah, Ky as it's powered by TVA electricity which is in part, generated by coal, the rest coming from hydro (Hoover Dam, etc) and nuclear. But, an other example, the EURODIF gaseous plant uses off-peak electricity from the 4 Tricastin PWR reactors. That demonstrates that the enrichment phase can be CO2 free and that nothing specifically requires the use of fossil fuel for it, as opposed to, for instance, open pit mining where the trucks are fueled with diesel (yet shaft mining machines run mostly on electricity so ...).

And anyway, USEC and EURODIF are moving to centrifuge so those CO2 numbers are obsolete in any case and at least a 20x factor off not matter how the energy is produced.

As I'm cross-checking the Wise numbers, I note that the Wise slide has this comment:

The CO2 emissions increase considerably with decreasing ore grades, but are still by far lower than from electricity generation in fossil plants.

These figures cover only the operation of the fuel cycle facilities. The situation may change, if CO2 emissions from construction and decommissioning also are taken into account.

Emphasis mine. I love the ominous "caveat" about construction and decommissioning. "The situation may change..." Yeah, really? Can they show a credible scenario where building and destroying a nuclear plant would significantly alter the CO2 balance?

For reference, a 1,600 MW EPR reactor requires 250,000 m3 of concrete, about 200,000 t of cement if it's all high compressive strength concrete, that is 250,000 t CO2 (1.25 t CO2 for 1 t cement on bad days).

There are other sources for CO2 building a plant - transporting all the stuff on and off site, etc. - but, at least, that quick calculation gives an order of magnitude for the most obvious CO2 suspect - concrete in the plant. If the life cycle of an EPR plant emits more than 2 million ton of CO2 excluding the fuel cycle itself, someone needs to show me a detailed, fully sourced analysis.

And an EPR will produce 80 to 100 GWa_e over its lifetime, so reducing those hypothetical 2 million ton of CO2 to each GWa_e, that's a 25,000 t CO2 increment to the 300,000 t to 600,000 t CO2 per GWa_e numbers given by Wise for the front-end fuel cycle.

In other words, their little innuendo is 100% bullshit. They can't demonstrate their point so they punt to an unevaluated issue, knowing most will swallow it without asking questions.

For the rest of the slide, I don't know where their numbers are coming from but given what shows up when I look at the enrichment numbers, I'm entitled to have my doubts.

There's no direct URL for the slide I refer to. Watch the whole slide show for yourself. If you select all chapters, the slide in question is #67, next to last.


Dodo, that's the problem with all those "green" think tanks. They tweak and spin the numbers to match the goal. Everywhere you peek, you find enormous claims, gross obfuscation and numerical hierophancy at every corner and when you cross-check, the balloon pops invariably.

And compared to other offenders like Greenpeace, Wise is positively tame. Given the bull they pull on CHP, I suspect that Öko-Institut is more in the Greenpeace league.

by Francois in Paris on Sun Jul 15th, 2007 at 04:35:29 AM EST
[ Parent ]


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