Nuclear CO2

A while ago I posted tangenitally on the CO2 output from Nukes here. Now a new study (whose reliability I have no way of assessing) says:

The nuclear process emits 2-6 grams of carbon equivalent per kilowatt-hour, while coal, oil and natural gas emit 100-360 grams of carbon per kilowatt-hour [1].

(actually thats The Age's paraphrase; hopefully they can report figures accurately).

After my last post, an anonymomous commenter pointed me to the opendemocracy posting which asserts that:

A complete life-cycle analysis shows that generating electricity from nuclear power emits 20-40% of the carbon dioxide per kiloWatt hour (kWh) of a gas-fired system when the whole system is taken into account.

Hmm... how do we reconcile these two estimates? Firstly gas is better than oil or coal so perhaps we can take the "100" from the first; but even then taking the "6" from the first and the lowest, 20%, from the second we have 6% compared to 20%, a factor of 3 disparity. Unfortunately the source for the second lot (http://www.oprit.rug.nl/deenen/) is currently offline.

Based on a simple argument (I think most of the monetary costs of nukes is engineering and safety and disposal; if the CO2 costs were really 40% nukes would probably be even more uneconomic than they are) I'm disinclined to believe the second set. That doesn't mean I do believe the first, though.

I do agree with SB on the comments to my first post: that there are vast energy efficiency gains possible. BS's argument that nukes are too safe is worth reading too. But having said that, any other refs to nukes CO2 would be welcome.

Oh... and this *isn't* going to become an energy-sources blog... back to the science soon!


Brian said...

Reading the article carefully, it's not clear that the 2-6 gram figure includes the uranium refining emissions. While they discuss refining emissions earlier, they don't expressly say those emissions are included in the "process" figure.

Maybe that accounts for the discrepancy.

Another possibility is the difference lies between their theoretical best way to produce nuclear power versus how it's actually done. The same problem is present here in the US regarding analyses of the wonderful issue of ethanol.

William M. Connolley said...

I think being optimistic or pessimistic about various bits, and which bits you leave in (does the CO2 that all the safety people emit from the things they buy from the money you pay them count?) or out accounts for it. Which makes it pretty hard to know what the real numbers are. Anyone with enough time to study it to death is liable to have an agenda...

Eric McErlain said...

My colleague David Bradish has been looking over the numbers in many of these studies and found them wanting. Click here for more.

EliRabett said...

The two emissions sources which cannot be escaped are those associated with concrete manufacture and the costs of moving earth and ore in uranium mining. The latter are much less than for coal.

William M. Connolley said...

Eric - thanks for the link & numbers. In the second comment there, "If uranium took so much money, or energy, to extract, why would we build nukes (i.e., how could they be economic)?" replicates one of my meta-arguments. But its a slightly weak one, because a possible answer is that nuclear *isn't* economic. You can't tell from the outside.

For those who didn't follow, http://www.world-nuclear.org/info/inf11.htm provides a table of CO2 emissions per power output, which shows a 20-fold advantage for nuclear (exact value depends on source: look at the table for more; its about 3/5 of the way down). The caveat, of course, is that all this is from an organisation that you might expect to be pro-nuclear.

Anonymous said...

This subject has been well covered in the book "Nuclear is not the Answer to Anything" by Helen Calidcot. In the book she goes to a lot of effort to spell out the emmisions areas, the quantities and studies related to the topic. She also points out where and how the industry is supported by tax payer dollars and how very expensive an option it is without this support. 2-6 grams is in no way acurate and would put Wind power above nuclear for emisions.