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Fossil Fuels coal-emits-95-percent-more-ghgs

Published on May 7th, 2012 | by Susan Kraemer

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NREL Lends Legitimacy to Life-Cycle Assessment of Coal v Renewables

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May 7th, 2012 by
 
coal-emits-95-percent-more-ghgs

An average of LCAs at the Journal of Industrial Ecology finds that burning coal generates 20 times more greenhouse gases than construction projects that generate energy such as solar or wind farms. Wind and solar generate averages from 10-50 grams to coal’s 1,000 grams of CO2 to generate 1 kilowatt hour of energy.

The NREL helped consolidate reams of studies of lifecycle assessments (LCAs) of carbon emissions as compared between coal and renewables. They find that renewables emit the same sorts of (negligible) amounts of greenhouse gases that most activities (other than generating electricity from coal) do.

But why there have been so many studies of something that is so obvious, is a mystery. It almost makes it seem that there could be some question that renewables are in any way comparable to coal. Perhaps all these LCA comparisons were commissioned by the coal industry grasping at straws to generate media to the effect that wind, solar emit greenhouse gases too, so nah, nah, nah-nah-nah!

Talk about tilting at windmills.

Here is what is assessed for wind, to calculate its LCA:

  • One-time upstream emissions, which includes emissions resulting from raw materials extraction, materials manufacturing, component manufacturing, transportation from the manufacturing facility to the construction site, and on-site construction.

  • Ongoing emissions during the turbine’s operating phase, which includes emissions from maintenance activities such as replacement of worn parts and lubricating oils, and transportation to and from the turbines during servicing.

  • One-time downstream emissions, which includes emissions resulting from turbine and site decommissioning, disassembly, transportation to the waste site, and ultimate disposal and/or recycling of the turbines and other site materials.

Transmission and distribution (T&D) of electricity is sometimes included within the scope of LCAs, either through accounting for construction of the infrastructure or the loss of generated electricity in delivery to the consumer, or both.

But seriously. Other than creating energy from Tinkerbell’s pixie dust, what possible source of energy would not be made out of stuff and moved there? Only something made of thin air would not have some “emissions resulting from raw materials extraction, materials manufacturing, component manufacturing, transportation from the manufacturing facility to the construction site, and on-site construction.”

But we need to compare wind to coal, not to some Tinkerbell pixie dust energy source that we could use instead of wind that’s not made of stuff.  Just like everything we build for long term use, from skyscrapers to bridges, wind and solar is first made from stuff and then moved to the site (where it does generate energy from thin air).

Stories on these findings will tut tut that indeed wind and solar have [some trivial and truly insignificant] carbon emissions, so that therefor they too are “just like coal” even though coal really does have serious civilization-altering carbon emissions.

So you can count on seeing headlines like “Solar, Wind Have Carbon Emissions Too”. For example, intones Phys.org earnestly:

“State and local lawmakers, weighing the merits of a new coal-fired plant versus a wind farm, for example, are eager to know not just the relative financial costs, but the impacts to the environment over the decades the project.”

“Eager to know”? You have to be kidding. “Weighing the merits of a new coal-fired plant versus a wind farm”? Like it might be a tossup?

What is more, I can’t speak for the accuracy of the coal data, but the renewable energy assessment data used in these studies is ridiculously flawed and out of date.

The solar PV data makes one huge error, in assuming that the life of a solar panel ends after 20 or 30 years. But that date is only when manufacturers warranties expire, because after 25 years, solar produces 12% less than the initial rated power, since they could then be sued for it not producing the originally rated power. But in fact solar panels produce (at reduced efficiency) for at least 40 years and we don’t know yet how much longer, because the panels first manufactured 40 years ago are still going.

This would skew the solar results since less power would be recouped to amortize the carbon cost of making them.

Similarly, Notes on the wind data used suggests it was overly weighted towards small wind turbines averaging 600 kilowatts. But in the surge in wind farms that provide the bulk of the U.S. wind industry now turbines under 1.5 MW are virtually never used and certainly will not be used in future installations. In Europe it is more like 3 MW.

Where they found utility scale wind farms with 225 kW – 600 kW turbines is a mystery. Maybe the few in California in the Jimmy Carter era were 225 kW, but they are being replaced.

d This data point represents a mix of (4) 660 kW, (4) 600 kW and (2) 1.75 MW turbines. Therefore, a capacity-weighted average capacity factor was used to allow for harmonization for this step. e The capacity for this data point represents a weighted average of (1) 225 kW, (1) 500 kW, (7) 600 kW, and (1) 1.75 MW turbines. A capacity-weighted average capacity factor was used for harmonization of this step. f The capacity for this data point represents a weighted average of the mix of (7) 600 kW, (4) 850 kW, (10) 1.5 MW, (63) 2.0 MW, (50) 2.3 MW, (30) 3 MW turbines. A capacity-weighted average capacity factor was used for harmonization of this step.

Of course if you assess solar that has to be thrown out in 20 years or wind that has the feeble power of the 1970s, then the LCA will look worse for them compared with coal.

So while the summary is that solar and wind power emit some 5 tons of CO2 for every 100 tons emitted by coal power, I have my doubts.

 

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About the Author

writes at CleanTechnica, CSP-Today, PV-Insider , SmartGridUpdate, and GreenProphet. She has also been published at Ecoseed, NRDC OnEarth, MatterNetwork, Celsius, EnergyNow, and Scientific American. As a former serial entrepreneur in product design, Susan brings an innovator's perspective on inventing a carbon-constrained civilization: If necessity is the mother of invention, solving climate change is the mother of all necessities! As a lover of history and sci-fi, she enjoys chronicling the strange future we are creating in these interesting times.    Follow Susan on Twitter @dotcommodity.



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  • Bill_Woods

    “Wind and solar generate about 5 grams to coal’s 100 grams of CO2 to generate 1 kilowatt hour of energy.”

    Both these numbers seem low, but the coal figure is very low — did you mean 1000 g/kW-h?
    http://en.wikipedia.org/wiki/Comparisons_of_life-cycle_greenhouse-gas_emissions

  • Bill_Woods

    “… burning coal generates 95% more greenhouse gases than construction projects that generate energy such as solar or wind farms.”

    Coal only generates about twice as much? That’s not very impressive. Perhaps you meant wind or solar generate 95% less than coal? (I.e. coal generates 20 times more?)

    The figures I recall are that fossil fuel emissions are in the 100s of grams of CO2 per kilowatt-hour, while clean-energy emissions are in the 10s.

    • http://importantmedia.org/author/susan Susan Kraemer

      Oh, very good point. Yes, that is what I meant. Jeez!

    • http://muckrack.com/dotcommodity Susan Kraemer

      You are right, that was one terrible math typo. Thank you so much for catching it Bill. In fact it is 20 times as much – solar and wind were 95 % less.

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