A shale’s life: first life cycle assessment of shale gas used for electricity in Great Britain

An interesting article came out a few days ago in Applied Energy that is of particular importance because its directly relevant to current politics in Great Britain.  With an estimated 38 trillion cubic meters of shale gas estimated to be lurking underneath the streets and hills of England, the country has the potential to fulfill all its gas needs for about 45o years.  While this is exciting news for many, opposition is quite strong due to the perceived environmental risks, as I’ve discussed before.  The cool part is what’s happening now to clarify the issue a bit.  The author of this Applied Energy paper, Adisa Azapagic of the University of Manchester, presented the findings at the Labour Party Conference yesterday in Manchester.  A nice bit of science and policy coming together to try to get the solution right to the big global question right now – what to do about fracking?  The paper is quite long, and being in Florida I couldn’t make the jaunt over to Manchester, but I thought I’d try to highlight the main findings here.

1) What goes into a lifetime of fracking?

Just a quick review – a life cycle assessment basically takes every step involved in the entire lifetime of a product or procedure and estimates costs, material use, toxicity, environmental risks, etc.  The ‘entire lifetime’ part is crucial and can lead to some surprises.  For example, certain photovoltaics, usually thought of as the ‘greenest of the green’, can produce significant environmental waste materials when considering how to dispose of cells after use and the material wasted during the production process.  So it’s important to include all parts of the production process, not just what’s going on right when light is hitting the solar cell or the drill turns on to start fracking.

The life cycle of shale gas begins with exploring for desirable site, goes through the building of necessary equipment and vertical drilling, extraction, treatment of the shale gas for transport and use, transport for distribution, and final decommissioning of depleted sites.  As comparison, you can see below this life cycle compared to coal, nuclear, and renewables:

Figure courtesy of [1]

Figure courtesy of [1]

2) Global warming potential – between coal and renewables!

Figure courtesy of [1]

Figure courtesy of [1]

The authors found a central estimate of global warming potential over 100 years (GWP100) to be 462 g CO2-equivalent per kilowatt-hour.  This is less than 50% of coal’s GWP100, but an order of magnitude or two above renewables (this is renewables bread and butter in terms of advantages, though!).

This 462 g CO2-eq./kWh comes about to be about the same range as conventional gas production, which is a crucial results that shows that replacing conventional gas with shale shouldn’t impact global warming.  It takes about 4-20 times more carbon to extract shale compared to conventional gas, but this is made up for by reduced emissions for not requiring liquefaction (you need that for conventional gas!).

Overall, if Great Britain only replaces conventional gas with shale gas, no additional warming.  If some coal is replaced with shale production, even better – reduced emissions!

3) Element resource depletion – beats out renewables!

Here is a case where shale production beats the renewables.  Looking at depletion of physical, inorganic elements- they call it ‘abiotic potential’ – solar photovoltaics rate quite highly due to the use of silver and tellurium for certain thin film types of cells.

Figure courtesy of [1]

Figure courtesy of [1]

The situation is basically reversed in the case of abiotic fossil fuel resources, which is quite obvious, since the non-renewables are by definition fossil fuels.  Solar PV, wind, and nuclear require much less of this stuff.

3) Acidification – room for improvement!

Here’s a major finding – shale gas has four times the potential for significant acidification compared to coal and other conventional gas production.  This is mainly due to diesel combustion used to power the drill in fracking, as well as hydrogen sulfide used in the extraction process.  If the drill could be powered in another way, say by the grid, and a replacement for H2S could be found, this potential for acidification of groundwater, etc. could significantly reduced.

Politicians – here’s a clear result from science that you can use to direct policy!

4) And all the rest…

The paper looked at many other factors – toxicity to freshwater and marine life, human toxicity, ozone depletion, and photochemical oxidation.  Shale production (and conventional) are actually much better than any of the other alternatives for marine toxicity, and on average the potential for human toxicity is much lower compared to nuclear, solar, and coal (why solar you may ask?  There are some very toxic materials like cadmium used in some types of solar cells – I imagine this is where the toxicity potential is coming from, but the authors don’t explain completely…I’d like to see more on that!).

Ozone depletion seems to be about the same as conventional gas, which unfortunately is higher than most of the other alternatives.

Conclusions

The main take-home here, I think, is that shale gas production is much better than coal in terms of global warming potential and toxic potentials, and just as good/bad as conventional gas.  This seems to indicate that it could be an acceptable replacement for both.  Ozone depletion is a problem, as well as acidification, but at least the acidification problem could be remedied with adroit policy decision making by changing drilling power sources and removing hydrogen sulfide from the mix of chemicals used to treat the gas.  I think we should never see shale gas as the long-term solution, but if we can continue to view it as a bridge from our coal/oil-dominated energy market to a renewable one, then it seems to be a good short-term solution for Great Britain.

I go back and forth on this often because the environmental anecdotes in the US do seem pretty terrible (water wells lighting on fire, for example).  But I also know we need to get our energy from somewhere, and I don’t want to be lost in the clouds believing that we will suddenly make policy decisions to build solar cells on every rooftop.  Shale may be a necessary evil to bridge the gap, and this study suggests it may not be TOO evil for the job.  Just keep investing in renewables while we drill!

References

1)

ResearchBlogging.org

Stamford, L., & Azapagic, A. (2014). Life cycle environmental impacts of UK shale gas Applied Energy, 134, 506-518 DOI: 10.1016/j.apenergy.2014.08.063

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