U.S. Leads in Reducing Carbon Emissions, Due to Natural Gas, Despite Howarth

Natural gas development is allowing the United States to achieve carbon emission reductions no one thought possible even a few short years ago.  The International Energy Agency indicates the U.S. has, incredibly, led all developed nations in reducing its carbon dioxide emissions since 2006.  Some Cornell University natural gas opponents deny this reality and suggest it is also offset by methane emissions, but their theories have now been discredited almost everywhere.

We’ve heard a lot about carbon over the last several years and most of it has been to the effect the U.S. wasn’t doing enough to reduce emissions because it didn’t sign on to this or that agreement.  Notwithstanding this criticism, our nation has been the one leading the charge among world nations in terms of actual results, due in no small part to the availability of an option many other countries lack – the ability to develop natural gas resources using hydraulic fracturing technology on a large scale.

Hydraulic fracturing technology is hardly new, but being able to combine it with horizontal  drilling has increased efficiency tremendously and simultaneously made the U.S. a leader in both natural gas production and carbon emissions reductions; which is no coincidence.  Some natural gas opponents out of Cornell University (Robert Howarth, Tony Ingraffea and Renee Santoro) would have the world believe it is one, though, and suggest methane emissions more than offset any gains.  Using Park Foundation funding, they have speculated natural gas, over its production and use life cycle, somehow generates more total greenhouse gas emissions (carbon and methane) than coal, but the evidence contradicts their theory.

When Howarth, Ingraffea and Santoro came out with their theory natural gas was somehow the dirtiest source of energy in terms of total emissions over production and use life cycles, there was great excitement in the anti natural gas world this might, finally, be the game changer they had repeatedly sought and about which natural gas opponents had cried wolf so many times.  They produced two reports which, respectively, stated the following (emphasis added):

Indirect Emissions of Carbon Dioxide from Marcellus Shale Gas Development – June, 2011

In this report, we estimate the emissions of carbon dioxide associated with all fuel combustion associated with the shale gas life-cycle focusing on the Marcellus shale as a case study. We calculate all GHG emissions from land clearing, resource consumption, and diesel consumed in internal-combustion engines (mobile and stationary) during well development. Energy consumed once the gas well is brought into production (i.e. that consumed in production, processing, and transmission / distribution streams) are assumed to be similar to previously published estimates; therefore, we use emission intensities from the literature for these sources. Additionally, we do not address fugitive and vent emissions here. Rather, the reader is directed to our companion paper (Howarth et al., 2011), which emphasizes the importance of methane venting and leakage, concluding that in fact shale gas has a larger greenhouse gas footprint compared to other fossil fuels.

We estimate total indirect CO2 emissions as between 1.17 and 1.69 g C MJ-1 (LHV), depending upon whether or not the raw gas requires processing. Compared to the direct (i.e. end-use combustion) CO2 emissions: 15 g C MJ-1 (LHV), the indirect emissions are small, but not trivial. Our estimated indirect CO2 emissions from shale gas are 0.04 to 0.45 g C MJ-1 greater than that reported for conventional gas (Woods et al., 2011). Still, a far greater part of the greenhouse gas footprint of shale gas comes from methane venting and leakage (Howarth et al., 2011).

Methane and the Greenhouse-gas Footprint of Natural Gas from Shale Formations – June, 2011

We evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life-time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.

Both papers include serious flaws identified by others but Howarth, et al have defended the second report in particular by noting it was published in the Climatic Change Letters journal and forever crowing it was peer-reviewed, the refuge of so many authors of faulty studies it seems, like this peer-reviewed California study claiming dust caused premature deaths.  Attaching “peer-reviewed” as a permanent adjective to one’s study is no guarantee of good science.  Nonetheless, to the credit of Climatic Change Letters, it also published a critique of this work by Larry Cathles and several other members of the faculty at Cornell University, stating the following:

Natural gas is widely considered to be an environmentally cleaner fuel than coal because it does not produce detrimental by-products such as sulfur, mercury, ash and particulates and because it provides twice the energy per unit of weight with half the carbon footprint during combustion. These points are not in dispute. However, in their recent publication in Climatic Change Letters, Howarth et al. (2011) report that their life-cycle evaluation of shale gas drilling suggests that shale gas has a larger GHG footprint than coal and that this larger footprint “undercuts the logic of its use as a bridging fuel over the coming decades”. We argue here that their analysis is seriously flawed in that they significantly overestimate the fugitive emissions associated with unconventional gas extraction, undervalue the contribution of “green technologies” to reducing those emissions to a level approaching that of conventional gas, base their comparison between gas and coal on heat rather than electricity generation (almost the sole use of coal), and assume a time interval over which to compute the relative climate impact of gas compared to coal that does not capture the contrast between the long residence time of CO2 and the short residence time of methane in the atmosphere. High leakage rates, a short methane GWP, and comparison in terms of heat content are the inappropriate bases upon which Howarth et al. ground their claim that gas could be twice as bad as coal in its greenhouse impact. Using more reasonable leakage rates and bases of comparison, shale gas has a GHG footprint that is half and perhaps a third that of coal.

Numerous other studies, including a recent (and also peer-reviewed) Massachusetts Institute of Technology (MIT) report have similarly found the Cornell study to be deeply flawed.  We also now increasingly see rigs and compressor stations powered by natural gas, meaning the diesel use assumptions of Howarth, et al are more wrong every day.  Moreover, their estimates of carbon emissions depend largely on their assumptions about land clearing and loss of carbon sequestering forest land associated with natural gas development, which are highly questionable (e.g., 12.4 acres of land disturbance is involved with each well pad when pipelines and access roads are included).

The criticism of the Howarth report from independent experts has been nothing less than intense, for all these reasons.  Nevertheless, the academic speculation on either side is far less impressive than the actual results.  According to the International Energy Agency (emphasis added):

CO2 emissions in the United States in 2011 fell by 92 Mt, or 1.7%, primarily due to ongoing switching from coal to natural gas in power generation and an exceptionally mild winter, which reduced the demand for space heating. U.S. emissions have now fallen by 430 Mt (7.7%) since 2006, the largest reduction of all countries or regions. This development has arisen from lower oil use in the transport sector (linked to efficiency improvements, higher oil prices and the economic downturn which has cut vehicle miles travelled) and a substantial shift from coal to gas in the power sector.



These benefits were certainly not unexpected.  Climate advocate Joe Romm wrote a column for Grist in 2009, for example, where he pointed out how natural gas could help us achieve most of the emissions reductions sought under the cap and trade bill advanced by Reps. Henry Waxman and Ed Markey.  Romm wrote: “natural gas alone could meet a great deal of the Waxman-Markey CO2 target for 2020.”

That legislation would have required a 17% emissions cut from 2005 levels by 2020. EIA data reveal an interesting trend, though: First quarter carbon emissions in 2012 are already 14 percent below first quarter emissions in 2005. This is, of course, thanks in large part to increased natural gas utilization, as noted by the EIA.

Reality applies to more than carbon emissions; it also plays out with methane emissions. The MIT review, importantly, utilized actual field data to determine methane leakage was somewhere in the realm of 0.4 to 0.6% – far below the widely panned theory of Howarth, et al.  Findings from three separate laboratories within the U.S. Department of Energy have also affirmed lifecycle greenhouse gas emissions from natural gas – including shale gas – are roughly half those of coal. Finally, EPA data show methane leakage from oil and gas systems are a small source of the nation’s greenhouse gas emissions – less than 4 percent.

Natural gas is also critical to ensuring sound and robust growth of renewable energy sources, due to the need for reliable and efficient base load power backup. This was noted in The Golden Age of Gas published by the IEA in 2012.  The IEA, in this instance, stated “natural gas has an important role to play in complementing low-carbon energy solutions by providing the flexibility needed to support a growing renewables component in power generation.” IEA also noted natural gas, as a result, “could deliver long-term environmental and energy security benefits.”

The understanding natural gas co-generation is a necessary complement for renewable energy is, likewise, very well understood. Climate Progress, among many others, has acknowledged this. Under the heading “Wind and Solar Work Best With Natural Gas,” Climate Progress wrote (emphasis added):

Natural gas power plants are load-following power plants, which can shut down when the solar or wind resources are available. This is not true for nuclear or coal power plants, which are designed to run all the time.  Thus, an electric grid comprised more heavily of natural gas load-following power plants is capable of adding a higher proportion of electricity generated by the wind and the sun.”

Additionally, the benefits of natural gas use in reducing carbon emissions were also neatly summarized by Rajendra Pachauri, chairman of the International Panel on Climate Change (IPCC), recently in Doha:

Natural gas is the fossil fuel that produces the lowest amount of GHG per unit of energy consumed and is therefore favoured in mitigation strategies, compared to other fossil fuels.

Given the fact 90% of all oil and natural gas wells undergo hydraulic fracturing, it stands to reason this technology will remain a critical element in any serious climate change mitigation strategies deemed necessary by the United States.

Despite this, Howarth, et al are unrelenting in their determination, against the weight of evidence assembled by their peers, to perpetuate the opposite, and demonstrably false, idea natural gas is a loser.  Reality confronts.  Natural gas is a huge winner, economically and environmentally.  More specifically, if climate change is the problem, natural gas is the solution.


  1. Bill Ferullo says:
  2. Vita! says:

    Oh, Yoko…

  3. Bill Ferullo says:

    ” Natural gas is the fossil fuel that produces the lowest amount of GHG per unit of energy consumed and is therefore favoured in mitigation strategies, compared to other fossil fuels. “…..BUT it does produce increased methane which is approximately 21 – 25 X a GHG …!!!!!!! venting ,flaring ,compressor and facilities emissions ,well leaks ,pipeline leaks ,and CNG emissions from vehicles if we get there .

  4. Bill Ferullo says:

    ” Atmospheric methane
    Main article: Atmospheric methane

    2011 methane concentration in the upper troposphere[36]
    Methane is created near the Earth’s surface, primarily by microorganisms by the process of methanogenesis. It is carried into the stratosphere by rising air in the tropics. Uncontrolled build-up of methane in the atmosphere is naturally checked — although human influence can upset this natural regulation — by methane’s reaction with hydroxyl radicals formed from singlet oxygen atoms and with water vapor. It has a net lifetime of about 10 years,[37] and is primarily removed by conversion to carbon dioxide and water.
    Methane also affects the degradation of the ozone layer.[38][39]
    In addition, there is a large (but unknown) amount of methane in methane clathrates in the ocean floors as well as the Earth’s crust. Most methane is the result of biological process called methanogenesis.
    In 2010, methane levels in the Arctic were measured at 1850 nmol/mol, a level over twice as high as at any time in the 400,000 years prior to the industrial revolution. Historically, methane concentrations in the world’s atmosphere have ranged between 300 and 400 nmol/mol during glacial periods commonly known as ice ages, and between 600 to 700 nmol/mol during the warm interglacial periods. It has a high global warming potential: 72 times that of carbon dioxide over 20 years, and 25 times over 100 years,[40] and the levels are rising. Recent research suggests that the Earth’s oceans are a potentially important new source of Arctic methane.[41]
    A Bristol University study published in Nature claims that methane under the Antarctic Ice Sheet may yet play an important role globally. Researchers believe these sub-ice environments to be biologically active, in that microbes are converting organic carbon to carbon dioxide and methane.[42]
    Methane in the Earth’s atmosphere is an important greenhouse gas with a global warming potential of 25 compared to CO2 over a 100-year period (although accepted figures probably represent an underestimate[43]). This means that a methane emission will have 25 times the effect on temperature of a carbon dioxide emission of the same mass over the following 100 years. Methane has a large effect for a brief period (a net lifetime of 8.4 years in the atmosphere), whereas carbon dioxide has a small effect for a long period (over 100 years). Because of this difference in effect and time period, the global warming potential of methane over a 20 year time period is 72. The Earth’s atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases (these gases don’t include water vapor which is by far the largest component of the greenhouse effect).[44] Usually, excess methane from landfills and other natural producers of methane is burned so CO2 is released into the atmosphere instead of methane, because methane is a more effective greenhouse gas. Recently, methane emitted from coal mines has been successfully utilized to generate electricity. “

  5. Nancy Schmitt says:

    Howarth doesn’t represent Cornell University. He represents himself and the Park Foundation. His study has real consequences, though. It’s being used to justify new coal-fired power plants in Asia. I hope the Park Foundation likes what it paid for.


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