 A boom in natural gas activity, thanks in large part to fracking advances, has prompted the question: Is natural gas the way to transition between fossil fuels and renewables? Especially vis-a-vis the climate? It's an ongoing debate in science circles. (Duke University/Scottee Cantrell) |
A recent paper argues that natural gas helps make the transition to a low-carbon ... eventually. But is that good enough? Let's do some sleuthing.
There's been a whole lot of energy expended in the debate about the role of natural gas in the nation's and world's energy future. Much of this debate centers around the practice of horizontal drilling and hydraulic fracturing (fracking), techniques that have opened vast reserves of shale gas for exploitation but have also sounded alarm bells for many because of concerns about fracking's environmental impacts, especially on drinking water. (For concerns, see here, here, here, here and here.) Today's focus is on another one of those environmental concerns.
Another pretty hot, ongoing debate around natural gas is whether its use provides a climate benefit or not. Natural gas emits less carbon dioxide (CO2) per unit of energy generated than other fossil fuels. So for many years, the consensus was that substituting it for coal or oil would lead to less global warming. (See here and here [pdf].) And so it's been argued that it would be a valuable "transition fuel," something that could be used in place of coal or oil while the world gets its collective act together and develops a true low-carbon economy fueled by renewable sources (e.g., wind and solar) as well as, depending upon who might be doing the talking, nuclear. (See here, here, here and here.)
Interestingly enough, with the advent of fracking for shale gas and the consequent jump in estimates of natural gas resources (see here and here), the use of natural gas as a transition fuel actually seems to be feasible. Good news for the climate, one might conclude.
Not really, scientists like Bob Howarth of Cornell University, protested. Why? Before answering that, you need to know a couple of background facts. First, methane, the major component of natural gas, is itself a very potent greenhouse gas -- some 21 times more effective a warmer than CO2 on a 100-year basis. And second, when we use natural gas, there are inevitably fugitive emissions, leaks during mining, transport, and consumption that allow methane to escape into the atmosphere where it can do its global warming thing. What Howarth argued in a much-debated paper published last year is that the leakage rates are so high that, contrary to conventional wisdom, transitioning from coal to natural gas would actually lead to more global warming than just sticking with coal, even though coal is the most carbon-intensive of the fossil fuels.
Since the paper's publication, other investigators and studies have weighed in on the matter, including RealClimate's Gavin Smith; the Council on Foreign Relations' Michael Levi; Ramón Alvarez of Environmental Defense Fund and co-authors; and another Cornell scientist, Lawrence Cathles. But a definitive conclusion has been elusive because the actual magnitude of these fugitive emissions remains very poorly defined.
The upshot of the debate about the importance of fugitive emissions has led to a general consensus that we need a very thorough investigation into the leakage issue. In short we need to first pin down the magnitude of fugitive emissions and then cut them down by locking the methane up. (See here and here.)
But now Cornell's Cathles argues in a new paper published last week in the journal Geochemistry Geophysics Geosystems that fugitive emissions may not be that sinister after all. Or at least not if natural gas is indeed used as a bridge fuel that is first phased in as coal and some oil are phased out and then eventually is itself phased out in favor of carbon-free energy sources.
Assuming periods of 50, 100, and 200 years to make the transition from coal to natural gas to renewables, Cathles's model calculations indicate that the long-term (i.e., multiple decades to century timescales) climate impacts of the fugitive methane emissions are relatively small. The reason is that methane has a relatively short lifetime in the atmosphere -- about 12 years. And so once natural gas is no longer used as a fuel, the methane in the atmosphere from fugitive emissions will be removed from the atmosphere and so the warming from those emissions will be essentially gone. CO2 on the other hand is long-lived and so, Cathles argues, over the long term using natural gas instead of coal or oil is preferable because less CO2 will have been emitted in that scenario. Well, it's preferable provided we use natural gas as a transition fuel that eventually gives way to even cleaner renewables and/or nuclear. And then there's the issue of the short-term climate effects from fugitive emissions.
Cathles's point about the transient effects of methane fugitive emissions is well taken. But there is a potential catch and it relates to short-term climate effects. During the transition period, when fugitive methane from using natural gas would build up in the atmosphere, there is a possibility, depending upon the magnitude of the methane emissions, that we would experience more short-term warming than if we were to have stuck with coal and oil. We might think of this as the transient version of the Howarth argument.
Now, as long as the fugitive emissions are small or the Earth system is "reversible," the transient Howarth scenario does not seem all that worrisome. But what if the emissions are large? And what if the disturbances from global warming are not reversible? Then we would have a problem. The transition to natural gas would lead to more warming for a period of time until natural gas is phased out and the excess methane is removed from the atmosphere. With the exit of the excess methane, the extra warming would also go away. Cathles seems to argue that all would be well:
"Even when methane leakage is so large (L = 10% of consumption) that substituting gas for coal and oil increases global warming in the short term, the benefit of gas substitution returns in the long term."
But it is not all that obvious that the impacts from global warming are reversible. If fragile ecosystems like coral reefs are decimated by a decade or two of extra methane-induced warming, can we be sure that they will recover once the methane is flushed from the atmosphere? Probably not.
Now for this to be a concern, fugitive emissions would need to be large -- about 10 percent or more. That's' a very remote possibility. Even so, Cathles's interesting results notwithstanding, I don't think we can ignore fugitive emissions and just assume they're too small to care about. And in any event from an economic and environmental point of view, the less of that stuff the better.
Cathles would agree. In fact he concludes his paper with the policy recommendation that leakage of methane related to natural gas production, transport, and use be reduced to about 1 percent. Let's call it the one-percent solution.
Crossposted with TheGreenGrok. Like us on Facebook.
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Frances Beinecke: Connecting the Dots on Climate Change
"Reversible", in terms of natural systems for CO2 reduction, isn't relevant below scales of tens of thousands of years.
Long term we need to go to rooftop solar, offshore wind and waste to energy and fuels for a truly 24/7 sustainable, forever, safe clean and cheap energy system.
There is nothing wrong with CARBON fuels, the problem is FOSSIL fuels.
Waste bio char for instance, can sequester massive amounts of carbon and replace fossils with cleaner waste bio fuels and local cogenerated heat and electricity.
(this requires we replace our commuting cars with electric charged by solar and wind to reduce out oil use 90% so our wastes can supply the rest.)
We can use the natural gas infrastructure with waste gases to backup solar and wind.
Using yup natural gas before a asteroid or earthquake releases it in mass quantities will prevent the next methane extinction. and serve as a backup for the emerging solar wind and waste systems.
But fracked gas threatens our fresh waste supply and must be stopped.
http://e360.yale.edu/feature/the_greenhouse_gasthat_nobody_knew/2085/
It was a real shame on so many levels the failure of Solyndra because unlike all solar cells manufactured in China the Solyndra process did not use NF3. C6F6 is about 12,000 times stronger than CO2 as a greenhouse gas from what I remember.
We had an AC unit replaced 3 years ago, and another replaced last year. I was there the entire time, and never once did I see a technician bring in a vacuum pump to recover refrigerant.
The main reason to avoid fugitive emissions is that they could cause an explosion. Distributors are keen not to have them.
The other main sticking point with the author's conclusions is the statement that a transition to renewable energy sources is even needed. Renewable energy from wind is barely more costly than natural gas at the present low prices. Another point left out is the fact that with mature wind and solar, there are no negative health impacts, and no fuel costs, and so long term costs are lower, and more predictable. If gas is needed, then it could be as standby power for variability issues of renewables. Variability issues have not been a big problem with levels of renewables in use. We can increase to 20% or more without much change in reliability. Wind sensors and a national database of wind flows allow accurate wind forecasting so standby needs can be determined with time to adjust. Solar power offsets daytime peak power and fits peak load closely. Battery technology is close to grid parity for power storage, geothermal is a proven technology that makes steady power as a base load source. Colorado to Achieve 30% Renewables Eight Years Early | CleanTechies Blog - CleanTechies.com
Battery to Take On Diesel and Natural Gas - Technology Review
Wind Levelized Cost of Electricity (LCOE) at All-Time Low - CleanTechnica
Solar Power Almost as Cheap as Natural Gas in Six States | CleanTechnica
Thermal power plants , nuclear, coal and gas, all consume huge fresh water resources, and return water elevated in temperature, and contaminated. Up to 1/3 of US fresh water withdrawals are for power plant cooling. Wind and solar do not have big water use, wind has none at all.
Thermoelectric cooling is the largest single user of non-saline water in the United States, even more than 1/3rd of total fresh water used, even more than the amount of water used in agriculture, according to the above diagrams.
Here in water hungry California, the two nuclear power plants use saline water.
The question on the amount of methane leakage has become mired in politics. Frankly, I suspect that it is not nearly as bad as many people claim.