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Still Not Worse Than Coal

At the end of last year I examined assertions by a professor from Cornell University, based on his unpublished paper, that leakage from natural gas production and transportation systems in the US resulted in lifecycle emissions for gas that were actually worse than those from coal. From what I saw at the time, I couldn’t agree with his conclusions. Now Professor Howarth’s paper is apparently about to be published, with a specific focus on shale gas. It has already been leaked via the New York Times and The Hill news site. After seeing the data and calculations supporting its claims, I am still not persuaded, though I would be quick to concede that the subject deserves a more thorough assessment by a body actually equipped to gather the necessary data and process it rigorously.

I don’t make a habit of reviewing scientific papers, but this one begs for a critique, for two reasons. First, it’s appearing in the middle of a crucial national debate on the potential risks of the techniques involved in unlocking the potentially game-changing shale gas resources that have been found in the US and elsewhere around the world. What better way to make those risks–which I believe to be entirely manageable–seem not worth taking than by portraying shale gas as having more adverse environmental consequences than the chief fuel its supporters see it displacing: coal. So at a minimum the paper demands careful scrutiny because of its potential significance to the debate surrounding the largest energy opportunity the US has uncovered in decades.

In addition, practically every paragraph includes an assumption, simplification or choice by the authors that tends to increase the calculated environmental impact of natural gas. Whether that’s the result of bias or merely a series of judgment calls, it undermines confidence in the final conclusions at the same time it amplifies them. I’ll focus on the most significant of these decisions and forgo the questioning of many individually less-important, though still cumulatively consequential details for others better equipped to tackle them.

Probably the most significant choice the authors made was to emphasize the global warming impact of methane (the main component of natural gas) over a 20-year period, in preference to than the more commonly used 100-year interval. Then they bypassed the established Global Warming Potential (GWP) factors from the UN IPCCC’s Fourth Assessment Report to use much higher factors for methane from a 2009 paper published in Science. I’ll leave the angels-on-a-pin debate over this to the climate scientists, but I don’t believe you need a Ph.D. in atmospheric physics to understand that if the outcomes of climate change will truly be determined in the next 20 years, we are already cooked. The world can’t get global emissions down by enough, fast enough, to solve the problem on that time scale, at least not without a global economic shock that would return hundreds of millions of people to poverty. So when I recalculated the paper’s estimate on shale gas emissions, I did so using the consensus 100-year GWP for methane of 25–less than 1/4 of the one on which the paper’s scariest results rely.

The other major choice the authors made was to ignore the downstream conversion of gas and coal into electricity. As lifecycle analysis, this earns a failing grade. It’s like comparing the overall emissions of a Nissan Leaf and Ford Explorer by focusing only on what happens upstream of the battery charger and the fuel tank. The authors dismiss this by saying that “this does not greatly affect our overall conclusion”. That’s wrong, not least because it’s precisely the comparison of how gas and coal actually compete with each other that matters most here.

On the basis of these two points alone, the paper’s conclusions crumble, even with the inclusion of supposed methane leakage rates from shale gas production that would have any engineer worth his or her salt scrambling to redesign the equipment so as to capture so much valuable “lost and unaccounted for” output. So how do shale gas and coal compare, on a full lifecycle basis from well and mine to the power plant bus bar, if 3.6-7.9% of gas actually leaked out during well completion, processing, transportation, storage and distribution, as Dr. Howarth’s paper suggests?

Let’s start at the power plant and work backwards. A current combined-cycle gas turbine unit requires around 6,700 BTUs of gas to generate a kilowatt-hour (kWh) of electricity. At the rate of 117 lb. of CO2 emissions per million BTUs of gas burned, that yields power plant emissions of 0.78 lb/kWh. But that’s on the basis of the gas that reaches the turbine’s combustor. We have to gross up that result to account for the emissions that occurred upstream of the plant. At Howarth’s estimated leakage midpoint of 5.75%, and using the standard 100-year GWP for methane compared to CO2 on a molar, rather than mass basis, that leakage would add an extra 55% of CO2-equivalent emissions from the well to the combustor, bringing the effective emissions from that combined-cycle plant up to 1.2 lb/kWh. For comparison, the most efficient coal-fired power plant I know of (without carbon capture and sequestration) emits about 1.75 lb/kWh. Only if we included inefficient, simple-cycle gas “peaker” units that don’t normally compete with coal would the upstream emissions that Dr. Howarth posits result in lifecycle emissions from gas-fired power worse than the typical coal-fired generation emissions of around 2 lb/kWh. In other words, the gas-fired generation that actually competes with existing coal plants still appears to emit nearly 40% less GHGs than its coal competition, even assuming the shale gas leaks that Dr. Howarth and his contributors reported.

Although my analysis admittedly falls into the back-of-the-envelope category, I’m not sure that the Howarth, et al paper is many notches above that level, given its reliance on non-peer-reviewed sources and its references to irrelevancies like Soviet-era gas systems. All in all, it seems a shaky edifice on which to mount such provocative conclusions. Perhaps all the authors wanted to do was to highlight some areas for the gas industry to investigate further, in order to ensure that methane emissions are kept to a minimum as shale and other unconventional gas deposits are developed. Unfortunately, it seems all too likely that its headline findings will be touted by those who are determined to stop the shale gas revolution in its tracks, or at least delay it for long enough that its utility in addressing our pressing energy problems will be lost. I wonder what Mr. Pickens thinks about all this, given that legislation promoting his plan to convert portions of the US truck fleet to natural gas, which depends on abundant shale gas supplies, has finally attracted bi-partisan support, including from the White House.

Photo by johnnyberg.

Content Discussion

David Lewis's picture
David Lewis on April 14, 2011

If there is a “chief fuel” that shale gas is replacing it is nuclear power.  The choice to go with gas and forget about new nuclear is being made now.  Powerful arguments exist that it is the wrong choice.  Our economic system can function by ignoring the cost of the damage the wastes of fossil fuels will cause, but it clear that the planet cannot.  Howarth’s work is a valuable contribution to the debate.  

 Gas and coal should have to limit their climate impact just as nuclear has to limit the impact of its wastes.

 The big environmental groups have given gas a “get out of the climate villain spotlight for free card” which has many thinking if the US ramps up gas and lowers its coal production it will actually be doing something about climate.  Because the environmental NGOs have granted gas this free pass and concentrated on stopping coal, the gas industry has been able to avoid limiting its climate impact. 

 Your argument, and I am surprised to hear you repeat it, that “any engineer worth his or her salt” would have scrambled by now to “redesign equipment so as to capture so much valuable lost and unaccounted for output” falls apart in the face of reality.  This chart, which shows methane leakage in two US oil and gas producing basins, is from the GAO report on methane leaks issued Oct 2010  Howarth had nothing to do with this. 


British Petroleum controls what happens in the N. San Juan basin, and they don’t in Uinta.  The light blue is the fantasy reporting the industry has been doing until recently, the dark blue is reality, confirmed by the EPA as well.  This is GAO assessed data, not Howarth’s.  The low leakage rate BP has in N. San Juan shows what happens when the company CEO says do something.  When Kyoto was signed, BP and Shell, as opposed to US companies, decided to throw in the towel on the climate science denial campaign and start to be seen to be doing something.  (See: What it took to wake some of them up on climate.  Note the comment on that post written by Dr. Bryan Lovell, a former senior executive at BP)   One thing BP decided it could easily do was go after methane leaks in its US operations.  They made money controlling these leaks.  US companies decided it would be easier just to lobby Congress to make sure they’d never have to take climate seriously. 

 High leak basins are typical in the US. 

 The engineers are not being allowed to “scramble” to deal with these leaks because their main task is to find and extract more oil and gas. They still use gas as if it were compressed air to power equipment.  They claim they have no leaks until someone points an IR camera at some and shows them. 


Oh geez, were we doing that?  The spokespeople for the oil and gas industry blew it when they commented on this GAO report – they did not dispute that the leaks are as bad as Howarth says.  What they said was the loss of revenue to Treasury was so miniscule it didn’t matter.  See:  Big Gas fumbles GAO report  

  The EPA finds that the leaks are there. 

 You know all this.  But it is Howarth, you say, whose whole thesis is shaky, because it relies on non peer reviewed sources and irrelevancies. I’ve read most of his peer reviewed references, and exchanged views with Howarth as well as one of the referenced authors.  He has solid material.  You’re picking at his case like a lawyer defending a client, and it is your arguments that don’t hold up.  Howarth argues like a scientist.  He’s been refining his case and lining up reference material for many months and subjected the whole case to peer review.  You’ve considered it on a “back of the envelope” basis. I think you should look at the paper with more attention, with the idea you should understand it, if its important enough for you to critique.  

 Your argument that if a 20 year time frame matters, “we are cooked”, is irrational.  Therefore we should do nothing?  The President of the National Academy of Sciences is on record identifying who he thinks the best climatologist is, i.e. Hansen.  Hansen says, yes, we’re cooked.  Hansen argues that in a similar way to after almost the entire Pacific Fleet was sunk by the Japanese after Pearl Harbor, we need to face the situation we’re in and deal with it.  At any point people decide to wake up and start dealing with reality, there will be significant things that can be done.  Young people, hearing you imply well lets just kill the planet its too late, which is fine for someone your age what do you care you’ve had your life, may decide they don’t need you or the entire fossil fuel industry. 

 I wonder at your argument that dealing with reality will cause all the poverty you speak of – the US did things as radical as retool its entire auto industry to make war materiel that was only useful to hurl onto distant battlefields to be wasted, it ran up debts people thought at the time could never be paid off, and it sent hundreds of thousands of its finest young people out to the front lines to die, yet after all this, after that war it emerged into an era of prosperity that lasted for decades afterward.  People regained confidence in the power government has to organize them and solve impossibly large problems, such as the ones we face now.  During the war many had the time of their lives working together on vital tasks that gave their lives meaning.  You’d be the guy in 1941 who’d be telling us we can’t retool 40% of our entire GDP for war, we’d better let Hirohito take over.

 The argument that we must stay with the assessment the IPCC made of the properties of methane makes no sense.  The cutoff date for reference material for them to consider was May 2006Shindell of NASA came up with the new data on methane GWP, not some back of the envelope blogger.  Howarth is saying he’s personally contacted some of the IPCC AR4 authors who assessed methane.  They say it is “appropriate” to use Shindell’s data now.  

 You’d be at a war council looking at a report that just arrived saying your entire army was about to be annihilated and you’d say oh lets leave this “angels-on-a-pin” debate to the military scouts, we should remain content with the 2006 report that said nothing was happening.  You’d accuse people who wanted to use the latest intelligence of “bypassing” 5 year old invalid information. 

 Now even if gas has about the same climate impact as coal, given that the reserves are on US soil, and given that coal has a lot of other bad attributes that gas does not have, gas is preferable to coal.  But it is not “green” from a climate point of view.  Its time this fact was incorporated into the consciousness of everyone in this debate.  



Geoffrey Styles's picture
Geoffrey Styles on April 14, 2011


I’d have been surprised not to see a comment from you on this one.  Let’s start with what I hope is a point of agreement: Shale gas shouldn’t be displacing nuclear power, except in locations where nuclear just can’t be built.  I’m not interested in a gas vs. nuclear debate. I see both as critical parts of a lower-emitting energy mix, although I don’t expect you’d share that view.  The opportunity shale gas presents is to back out high-emitting coal and imported oil (which is probably an emissions wash but an energy security gain.)

With regard to the methane leakage, whether from well completion or transportation, I don’t have the resources to dispute the figures, and you’ll note I performed my calculations on the basis of Howarth’s leakage assumptions. Having said that, I’d also note that the data in question appear to be at least several years old.  I’d be very interested in how such wells are being completed today, as the technology has matured significantly since then.  The gas production I’m familiar with goes through a gas/oil separator which splits gas and oil from water and routes them to their appropriate dispositions.  The idea of just venting 5-10 days of peak production (shale gas wells start out at maximum and then taper off fairly quickly) to atmosphere makes no sense.  That’d be throwing away a big portion of every well’s net present value.  I’d like to hear from someone who actually knows how these wells are completed and tied in.

As for the choice of GWP’s, it doesn’t make much difference whether the calculations are done with the 100-yr GWP for methane from the Fourth Assessment Report or from Shindell.  Even with the latter, a CCGT still emits up to a third less GHGs than a typical coal plant on a full lifecycle basis.  The key point of disagreement is over the use of 20-yr GWPs instead of 100.  I reject your characterization of my argument in favor of the latter as irrational.  Climate change is by definition a long-term problem.  Rejecting an option that would improve our long-term position substantially, by eliminating hundreds of millions of tons of coal plant CO2 that will stay in the atmosphere for centuries, on the basis that it would incur a short-term blip of higher GWP while the methane dissipates, would result in both more emissions and more climate change over the next century.

If your war council analogy means anything, then turning our backs on shale gas at this point is like sending the Pacific Fleet off to Midway without its carriers.  I’m in favor of reducing methane leaks to the maximum extent possible, and if that’s the net result of the debate that Howarth is provoking that’s good.  However, the leaks don’t justify leaving shale gas in the ground and continuing the status quo.  With the current uncertainties about nuclear, there’s a good chance that the share of low-emitting generation could actually decline, rather than grow, even as renewables ramp up in the next decade.  And if nuclear is stymied–and note that I’m not arguing against nuclear here–then gas represents our best option already at scale to back out meaningful quantities of coal-fired generation, which accounted for 32% of US energy-related GHG emissions in 2009. 

David Lewis's picture
David Lewis on April 14, 2011

I studied gas to critique the environmentalist NGO leadership who are pro gas anti nuke.  Now that Howarth’s paper has hit the NY Times, perhaps we’ll all hear from Michael Brune.  They’ve been pretending Howarth didn’t exist all this time.  One researcher for WorldWatch I contacted is as skeptical of Howarth as you are.  

I just saw your post and put up my comment for readers of your post to see.  I think I know where you stand on this and you must have a good idea where I come from.      

 I haven’t done any new gas research although I’m going to study this published version of Howarth’s paper.  

I’m studying radiation.  There has to be a better way to talk about it than what I’m hearing.  

I’m about to have gas put into my home.   The utility is paying part of the capital cost.  I’d put my own backyard reactor in but they probably have zoning regulations or something.  I thought I saw some used fuel rods on eBay – I think the ad said “only slightly melted” but I wasn’t sure.  It was in Japanese.  


Geoffrey Styles's picture
Geoffrey Styles on April 15, 2011

How deep would you have to bury one of NASA’s radioisotope thermoelectric generators (a.k.a. “nuclear battery”) to be safe?

David Lewis's picture
David Lewis on April 15, 2011

The heat source for those “nuclear batteries” is one of these 238PuO2 pellets. This one is glowing red.  

They used to use very tiny versions of these to power heart pacemakers for human beings.  Apparently (as of 2004) there were 90 human beings still running on plutonium. So much for the most dangerous substance on earth.  You get a long battery life out of it – after 25 years or so you still have 80% of the output you started with.  

The “nuclear battery” you are talking about that went up on Voyager probably put out 160 watts of electricity.  Exploiting the thermoelectric effect is very inefficient, so it also puts out a lot of heat – 2400 watts.  You could put the thing on your coffee table to entertain your guests with while it heated your house and powered your laptop and a few lights.  

The radiation from 238Pu can’t penetrate a paper bag.  The Voyager type was regarded as safely shielded by 1/10 of an inch of lead.  

But something that is more practical, i.e. what you really want if you need enough power to heat your whole home while producing enough electricity to run a one slice toaster is your own reactor. 

 This is a happy guy tinkering with one of the SNAP reactors like the one the US shot into orbit.  

He’s holding a fuel rod in his hand as he inserts it.  

David Lewis's picture
David Lewis on April 15, 2011

I like gas, except for that little detail that it hammers climate.  

Bringing up Midway is premature as an example because the attack on Pearl woke up the US population and changed it overnight from isolationist to ready for all out war.  By the time of Midway, the US had an overall strategy and was mobilizing all resources available in order to win that war.  So if the US population ever wakes up and changes from its current conflict over whether it even has a climate problem to being unified and ready to face it with whatever it takes, an analogy to Midway would be appropriate.  

At that time, maybe people would see the sense in going after that shale gas.  As part of a strategy aimed at phasing out CO2 emissions in a world becoming increasingly chaotic a power source like a lot of gas on US soil would not be discarded without serious examination of all alternatives.  It seems like it would certainly be used until no more coal emissions were going into the atmosphere.  

The big environmentalist NGOs like the Sierra Club have already bought into your line – they want gas to be the “transition” fuel to power civilization until whatever they imagine is going to replace all fossil fuels and all nuclear is created.  They’ve been trying to keep their followers in line even as they open their kitchen taps and find that the water catches fire.  I mean, they’ve pronounced whatever environment problems shale gas has are soluble.  

They denounce carbon capture on any fossil fuels, any approach to nuclear, tar sand oil is too dirty for them, Gulf oil is no good, Middle Eastern oil is too dangerous, etc.  They’ve got real problems with supply. They’ve been buying gas in a big way for that reason.  But they go where the public leads them in the end.  If the public won’t buy their line, it will change.  

Any solution to climate has to wait for the public to appreciate what is at stake.  A guy who sees the problem as deeply as anyone, Hansen, didn’t start advocating nuclear until he realized the climate situation was so far advanced civilization would now have to remove CO2 from the atmosphere to preserve any semblance of the planetary system it evolved on. I had been calling for returning the composition of the atmosphere to its preindustrial composition since 1988 and yet it took me until I saw how serious Hansen was about this for me to take a look at nuclear. I wasn’t some big opponent, but I wasn’t an advocate.  

With no overall climate strategy, we’re just drifting.  So, most observers would say at this point, what will it take to wake your ordinary person on the street up.  We’re going to drift until we see.  

Here’s my way of using the Midway example, perhaps inappropriately as well.   All US aircraft carriers were out of Pearl when the Japanese attacked. The big loss was to the old way many in the Navy thought was necessary to win wars in the Pacific, i.e. the battleships were sunk.  Afterward, the US was forced to attack a vastly superior Japanese fleet at Midway with what little they had left.  It happened that what the US had left was a relatively new power source in the naval arena, those aircraft carriers.  Although the victory also depended on brilliant leadership, superior intelligence that US code breakers provided, and a lot of luck, the US carrier fleet handed the Japanese a shattering defeat which changed the course of the war.    

Today the fossil fuels are the old way, like those battleships.  Civiilization might not survive losing the ability to use them, but it will not survive if it continues using them.  Denying that can’t change it.  Nuclear is something we’ve got left, thats as ready to go as the US carriers were when the mission was to eliminate a threat to the mainland US.  I say throw nuclear at the threat.  

I don’t see where developing more of what’s killing us is the way to go.