Climate change

April 7, 2009

Carbon footprint of the Olympic Dam uranium mine expansion

My home state of South Australia is host to the single largest known deposit of uranium in the world (by some estimates, up to 40% of the verified global reserves, although uranium is still poorly explored worldwide). The mine that was  first established over 30 years ago to exploit this resource (as well as copper [majority of production], gold and silver), Olympic Dam, is run by BHP Billiton, following their acquisition of Western Mining Corporation Resources in 2005. In that year, production was about 220,000 tonnes of copper and 4,600 tonnes of uranium oxide.

Late in 2008, despite some criticism, Premier Mike Rann gave the go-ahead for a $7 billon mine expansion. The eventual production of the enlarged mine — perhaps the largest ever man-made hole in the ground — is anticipated to be 730,000 tonnes copper, 19,000 tonnes of uranium oxide and 25 tonnes of gold per year. Critics have pointed out that the carbon footprint [e.g., diesel from vehicles and mining equipment] and electricity needs [possibly via gas-fired power plants] of this expanded enterprise would be massive — by some estimates almost 700 MW of extra electrical power demand. Greens SA MLC (State Senate), Mark Parnell, an active sustainability crusader here in this state whom I respect greatly, was quoted as saying: “Our state risks being left with a huge carbon black hole as we become the greenhouse dump for one of the world’s richest companies“.

Here I do a rough, back-of-the-envelope calculation, to test Mark’s ‘carbon black hole’ assertion with respect to the uranium extraction. My carbon footprint calculations are based on the careful figures derived for the highly detailed report by Bilek, Hardy, Lenzen and Day: Life-Cycle Energy Balance and Greenhouse Gas Emissions of Nuclear Energy in Australia (2006) [henceforth BHLD]. If in doubt, check the figures in that document yourself — its authors include three of Australia’s top life cycle analysts from the University of Sydney, who were commissioned by the Department of Prime Minister and Cabinet. I should note that a formal environmental impact statement for the Olympic Dam expansion, which will take into account many factors including water use and localised impacts, is due to be delivered in May 2009.

The current production of uranium oxide is about 4,600 tonnes, composed of a mixture of fertile 238U (99.29%) and fissile 235U (0.71%). Light water reactors (LWR) require enrichment of uranium oxide to 3 to 5% 235U, and once operational for a few years and running at a 90% capacity factor, need about 29 tonnes of enriched U per year per gigawatt of electricity (1 GWe) generated by nuclear power plants (BHLD, pg 79). It works out that in 2005, Olympic Dam produced enough fuel for roughly 22 GWe of generation capacity using today’s reactor designs (PWR/BWR), or 192,200 GW hours per year (GWh/yr). By comparison, the expanded Olympic Dam, with its anticipated output of 19,000 tonnes of U, would yield about 94 GWe of average power supply, or 794,000 GWh/yr.

Once the full nuclear life-cycle emissions for LWR are accounted for (includes: mining, milling, enrichment, fuel fabrication, reactor construction and operation, decommissioning and storage of spent fuel), the greenhouse gas intensity of the power generated is 60 kg CO2-e per MWhe (BHLD, pg 172), which is 60 tonnes per GWh [for fast spectrum reactors like the IFR, it would be substantially lower, since we skip the mining, milling and storage steps]. Thus in 2005 the emissions equivalent for Olympic Dam uranium mining was ~11.5 million tonnes (Mt) of  CO2-e. The expanded mine will be 48 Mt — that is, an additional 36.5 Mt of CO2-e will be released into the atmosphere each year as a result of the Olympic Dam expansion.

Okay, let’s put that figure in two different perspectives.

In 2005, South Australia’s total emissions were 28 Mt CO2-e. Let’s say that, despite our best efforts, our emissions continue to grow, such that in 12 years time they are 30% higher than in 2005, at 36 Mt CO2-e. The lifetime emissions that result from the mine expansion will be about the same as the total emissions of South Australia. Sounds bad, eh? Well, not to the atmosphere, which is a global commons.

Let’s say that uranium wasn’t available, and those French and Chinese (etc.) nuclear power plants were shut down and replaced with fossil fuel plants. Here is the comparison for the 2005 and 2020 (expanded mine) output based on three alternative power generation methods that yield the same total GWh/yr:

Black coal (supercritical): 2005 = 181 Mt CO2-e and 2020 = 747 Mt CO2-e

Brown coal (new subcritical): 2005 = 226 Mt CO2-e and 2020 = 933 Mt CO2-e

Natural gas (combined cycle): 2005 = 111 Mt CO2-e and 2020 = 458 Mt CO2-e

So, under the best-case gas alternative, we get an additional 410 Mt CO2-e dumped into the atmosphere each year if the Olympic Dam output was cancelled. With brown coal, the stuff we find powering Victoria’s Latrobe Valley (and feeding SA via the interconnector), we get an extra 885 Mt CO2-e. That’s a whopping 37% more than the estimated 530 Mt CO2-e we might expect Australia to be emitting from ALL emissions sources in 2020, assuming we manage to meet the 5% reduction target of the CPRS. Or looking at it another way, the Olympic Dam expansion will ‘offset’ South Australia’s total carbon emissions by around 13 to 26 times.

For a counter analysis on expanding our coal production see here: Save a bit here, ship a whole lot there.

So, to conclude, I agree with Mark Parnell that “Our state risks being left with a huge carbon black hole“. But not, as he imagines, if the Olympic Dam development goes ahead. No, that massive black hole (at least when expressed in terms of global climate change mitigation) will result from us NOT expanding the mine. Such is the huge energy returned on energy invested (EROEI) of uranium, even when used in today’s ‘inefficient’ once-through thermal reactors. In a future dominated by fast spectrum reactors with a closed fuel cycle, which use vastly more of uranium’s energy content, the above EROEI and emissions equivalence figures just get ridiculous.

Let’s get sensible about nuclear power and carbon emissions, shall we?

Update:
Other estimates of life-cycle emissions from world’s best practice are considerably lower than the 60 tonnes CO2-e per GWhe cited in the BHLD study above. For instance, there is this low-end estimate of is 3.3 tonnes CO2-e per GWhe given here:

There is world-wide concern over the prospect of Global Warming primarily caused by the emission of Carbon Dioxide gas (CO2) from the burning of fossil fuels. Although the processes of running a Nuclear Power plant generates no CO2, some CO2 emissions arise from the construction of the plant, the mining of the Uranium, the enrichment of the Uranium, its conversion into Nuclear Fuel, its final disposal and the final plant decommissioning. The amount of CO2 generated by these secondary processes primarily depends on the method used to enrich the Uranium (the gaseous diffusion enrichment process uses about 50 times more electricity than the gaseous centrifuge method) and the source of electricity used for the enrichment process. It has been the subject of some controversy. To estimate the total CO2 emissions from Nuclear Power we take the work of the Swedish Energy Utility, Vattenfall, which produces electricity via Nuclear, Hydro, Coal, Gas, Solar Cell, Peat and Wind energy sources and has produced credited Environment Product Declarations for all these processes.

Vattenfall finds that averaged over the entire lifecycle of their Nuclear Plant including Uranium mining, milling, enrichment, plant construction, operating, decommissioning and waste disposal, the total amount CO2 emitted per KW-Hr of electricity produced is 3.3 grams per KW-Hr of produced power. Vattenfall measures its CO2 output from Natural Gas to be 400 grams per KW-Hr and from coal to be 700 grams per KW-Hr. Thus nuclear power generated by Vattenfall, which may constitute World’s best practice, emits less than one hundredth the CO2 of Fossil-Fuel based generation. In fact Vattenfall finds its Nuclear Plants to emit less CO2 than any of its other energy production mechanisms including Hydro, Wind, Solar and Biomass although all of these processes emit much less than fossil fuel generation of electricity.

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