Material Inputs and Emissions – Insisting on Context

This infographic caught my attention, as it so clearly illustrates the sort of resource scarcity the world should be taking steps to avoid. Copper is in literally every modern convenience we enjoy. Scarcity pushes prices up. In the absence of conjectural polymer conductors or the like, there’s no real substitute for copper.

If you ever visit Moonta area, swing past the old mine sites. The green of residual copper ore is practically oozing out of the soil. Across the gulf, the new Hillside copper mine is already going ahead. And yes, I’d have one in my backyard. It’s called Kanmantoo, actually.

Isn’t it interesting that the infographic includes the copper required for the average megawatt (MW) of wind turbine capacity? 3.6 tonnes (t) per MW. Is this a lot? How does it compare to other material inputs? What about the greenhouse gas emissions that are involved?

The emissions intensity range of Australian copper mining was reviewed in Mudd et. al. as 2.5 to 8.5 tCO₂/t. Mudd, along with Diesendorf, also studied uranium mining emissions, and assigned an intensity of 10.3 tCO₂/t* to yellow cake produced at the Beverely in-situ leaching mine. The very thorough 2006 Australian nuclear power study by Lenzen (cited often by Diesendorf) estimates a requirement of 165 t of yellowcake annually per gigawatt (GW, 1000 MW). Therefore:

Australian copper in 1 GW of wind turbines = 9000 – 30600 tCO₂
Australian uranium in a 1 GW nuclear reactor = 1700 tCO₂

Accounting for the average modern capacity factor of annual generation (29% for Australian wind, 90% for nuclear, with ~8760 hours in a year):

3.54 – 12.05 tCO₂ per gigawatt hour per year (GWh/yr) of wind
0.22 tCO₂ per GWh/yr of nuclear

Of course, the wind turbines are erected once and should last for 25 years, while the uranium must be reloaded into the reactor effectively every year (in reality, refuelling occurs at 18 to 24 month intervals, and doesn’t involve the whole core). Yet these results indicate that a nuclear reactor would consume at least 16 years worth of uranium before equaling the mined metal emissions in a wind farm of equivalent capacity. At worst (50 years) the farm would potentially need to be replaced for a second time, while a modern nuclear plant is likely to have decades of life remaining.

And, of course, this is comparing apples and oranges. Apart from the fact that copper and uranium are both mined from the earth, they are clearly used for different purposes. So how much copper is needed for a nuclear plant? An answer is provided in a publication by Sovacool, another frequently cited name in these circles. A typical 1 GW plant apparently requires 729 t, which equals emissions of 1823 – 6197 t for Australian copper. That’s 20% of wind’s copper-related emissions, on nameplate capacity alone.

Now, I support wind and nuclear, both where appropriate, and I will stress that these figures, viewed as part of the comparative life-cycle assessments by reputable organisations such as NREL and the IPCC, are a negligible component – especially next to fossil fuels. The magnitudes don’t bother me, and indeed I don’t have any particular confidence in the source material. But when it comes to nuclear energy, and certain vocal critics, the context tends to get stripped away and various environmental impacts are presented as if they are exceptionally onerous. This is particularly galling when we consider that in Australia so much of both copper and uranium come from one place – Olympic Dam. In Mudd et. al., the authors propose a farfetched plan to power such sites with concentrating solar thermal plants, slashing the carbon intensity of the resulting copper. This would also reduce them for the recovered uranium!! Indeed, why not simply evaluate the best option for remotely and cleanly powering any given mine site, without being exclusive?

This small modular reactor design is being aggressively pursued by Holtec. It can be configured to be cooled by air instead of water.

 

*The authors provide a very questionable emissions estimate for uranium from Olympic Dam based on value rather than tonnage. Going by the estimated emissions rate of 0.11 tCO₂/t of ore from the 1997 environmental impact statement, and a proportion of tonnage (3,952 t yellow cake/187,000 t ore) of 2.1%, the share of emissions for uranium concentrate from Olympic Dam is 2.3 kgCO₂/t.

Further related analysis – cement and steel used in:
Wind – Can You Make a Wind Turbine Without Fossil Fuels?
Nuclear – Metal And Concrete Inputs For Several Nuclear Power Plants
Land area requirements, analysed fairly: How Much Land Does Solar, Wind and Nuclear Energy Require?
BBC Elements Podcast on Copper for materials and electricity.

 

Advertisement