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3.3% Methane (CH4) leakage & CH4 105 times worse than CO2 as a GHG => gas dirtier than coal GHG-wise

by Open-Publishing - Sunday 20 March 2011

Energy Environment Gideon Polya

Methane (CH4) is a major greenhouse gas (GHG) that on a 100 year time scale has a relative global warming potential (GWP) that is 25 times that of carbon dioxide (CO2).

However a re-assessment by US scientists that takes atmospheric aerosol responses to CH4 into account has found that on a 20 year time scale CH4 is 105 times worse than CO2 as a GHG (as compared to 79 without considering aerosol effects).

Recent data from the US EPA indicates that the industrial leakage of CH4 in the US is 3.3%. Using this information it can be estimated that gas burning for power can be much dirtier GHG-wise than coal burning.

Dr Drew Shindell and colleagues (NASA’s Goddard Institute for Space Studies) have published a paper in the prestigious scientific journal Science (US) that takes gas-aerosol interactions into account in assessing the GWP effectivenesss of various GHGs as summarized in the Abstract of their paper: “Evaluating multicomponent climate change mitigation strategies requires knowledge of the diverse direct and indirect effects of emissions. Methane, ozone, and aerosols are linked through atmospheric chemistry so that emissions of a single pollutant can affect several species. We calculated atmospheric composition changes, historical radiative forcing, and forcing per unit of emission due to aerosol and tropospheric ozone precursor emissions in a coupled composition-climate model. We found that gas-aerosol interactions substantially alter the relative importance of the various emissions. In particular, methane emissions have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol. Thus, assessments of multigas mitigation policies, as well as any separate efforts to mitigate warming from short-lived pollutants, should include gas-aerosol interactions.” [1].

The key technical quote from Shindell et al. (2009) provides an estimate that the GWP of CH4 relative to CO2 on a 20 year time scale is 79 (without aerosol effects) and 105 (with aerosol effects considered): “Fig.2. The 100-year GWPs for methane, CO, and NOx (per Tg N) as given in the [IPCC] AR4 and in this study when including no aerosol response, the direct radiative effect of aerosol responses, and the direct+indirect radiative effects of aerosol responses. The AR4 did not report uncertainties for methane or CO and gave no mean estimate for NOx. The range for the GWP of CO is from the third IPCC assessment and encompasses values reported up through the AR4. Our calculations for the shorter 20-year GWP, including aerosol responses, yield values of 79 and 105 for methane, 11 and 19 for CO, and –335 and –560 for NOx, including direct and direct+indirect radiative effects of aerosols in each case. The 100-yr GWPs for SO2 (per Tg SO2) and ammonia would be –22 and –19, respectively, including direct aerosol radiative effects only, and –76 and –15 adding indirect aerosol radiative effects. GWPs for very short-lived NOx, SO2, and ammonia will vary widely by emission location and timing, and hence global values are of limited use.” [2, 3]

The Nature News part of the prestigious scientific journal Nature (UK) has summarized the key findings of Shindell and colleagues as follows: “Aerosols’ complicated influence on our climate just got more threatening: they could make methane a more potent greenhouse gas than previously realized, say climate modellers. Drew Shindell, at NASAGoddard Institute for Space Studies, New York, and colleagues ran a range of computerized models to show that methane’s global warming potential is greater when combined with aerosols — atmospheric particles such as dust, sea salt, sulphates and black carbon. The International Panel on Climate Change (IPCC) and treaties such as the Kyoto Protocol assume methane to be, tonne-for-tonne, 25 times more potent than carbon dioxide at warming the planet. But the interaction with aerosols bumps up methane’s relative global warming potential (GWP) to about 33, though there is a lot of uncertainty around the exact figure.” [4].

Dr Shindell (NASA Goddard Institute for Spaces Studies, New York) has given a succinct summary of these findings: “What happens is that as you put more methane into the atmosphere, it competes for oxidants such as hydroxyl with sulphur dioxide. More methane means less sulphate, which is reflective and thus has a cooling effect. Calculations of GWP [Global Warming Potential;] including these gas-aerosol linkages thus substantially increase the value for methane.” [5].

This re-assessment upwards of the GWP of CH4 to be 105 times that of CO2 on a 20 year time scale must have a big effect on assessment of total annual GHG pollution and the urgency with which this is addressed.

Thus based on a 20 year scale CH4 GWP relative to CO2 of 72 (rather than 105) World Bank analysts have estimated that global livestock production contributes over 51% of total annual global GHG pollution that they have re-assessed upwards from 41.8 billion tones CO2-e (CO2 equivalent) to 63.8 billion tones CO2-e. [6].

Further, based on a CH4 GHG contribution 25 times bigger than that of CO2, eminent climate scientist Professor Hans Joachim Schellnhuber CBE (Director of Potsdam Institute for Climate Impact Research [PIK], Germany) has estimated that for a 67% chance of avoiding a catastrophic 2 degree Centigrade temperature rise (the EU target; would you board a plane if it had a 33% chance of crashing?) the World has to cease CO2 emissions by 2050. “All men are created equal” means that all human beings must be allotted equal shares of CO2 pollution until 2050. This in turn means that high annual per capita GHG pollution countries such as the US and Australia must reach zero CO2 emissions by 2020 while low per capita emitters (e.g. India and Burkina Faso) can increase their emissions until finally reaching zero emissions by 2050. [7].

Similarly, based on CH4 being 25 times worse than CO2 as a GHG, Dr Vicky Pope (Head of Climate Change Advice, UK Met Office Hadley Centre): “Latest climate projections from the Met Office Hadley Centre show the possible range of temperature rises, depending on what action is taken to reduce Greenhouse gas emissions. Even with large and early cuts in emissions, the indications are that temperatures are likely to rise to around 2 °C above pre-industrial levels by the end of the century. If action is delayed or not quick enough, there is a large risk of much bigger increases in temperature, with some severe impacts. In a worst-case scenario, where no action is taken to check the rise in Greenhouse gas emissions, temperatures would most likely rise by more than 5 °C by the end of the century. This would lead to significant risks of severe and irreversible impacts. In the most optimistic scenario, action to reduce emissions would need to start in 2010 and reach a rapid and sustained rate of decline of 3 per cent every year. Even then there would still only be a 50-50 chance of keeping temperature rises below around 2°C. This contrasts sharply with current trends, where the world’s overall emissions are currently increasing at 1 per cent every year.” [8].

On the same greatly under-estimated assumption, Professor Kevin Anderson and Dr Alice Bows (Tyndall Centre for Climate Change Research, University of Manchester, Manchester, UK): “According to the analysis conducted in this paper, stabilizing at 450 ppmv [carbon dioxide equivalent = CO2 -e, atmospheric concentration measured in parts per million by volume] requires, at least, global energy related emissions to peak by 2015, rapidly decline at 6-8% per year between 2020 and 2040, and for full decarbonization sometime soon after 2050 …Unless economic growth can be reconciled with unprecedented rates of decarbonization (in excess of 6% per year), it is difficult to envisage anything other than a planned economic recession being compatible with stabilization at or below 650 ppmv CO2 -e ... Ultimately, the latest scientific understanding of climate change allied with current emissions trends and a commitment to “limiting average global temperature increases to below 4 o C above pre-industrial levels”, demands a radical reframing of both the climate change agenda, and the economic characterization of contemporary society.” [9].

In short, the re-assessment that CH4 is 105 times worse than CO2 as a GHG on a 20 year time scale means that (a) the annual GHG must be over 50% greater than hitherto thought and (b) the time for 100% economic decarbonization must be substantially less than the current expert estimate of about 40 years.

A key aspect of economic decarbonization is obviously an urgent shift to non-polluting renewable energy (wind, wave, tide, concentrated solar thermal and solar photovoltaic) and geothermal energy.

However this transition has been falsely obfuscated by fossil fuel corporations and their associates in the Western Lobbyocracies who falsely assert that “gas is clean energy” or that “gas is cleaner energy than coal burning” and are hell-bent on a transition from coal burning to gas burning for power.

As a result of these false "gas is clean" and "gas is cleaner" assertions there is currently a major Gas Boom and Gas Rush around the world.

Professor Robert Howarth (Cornell University) has considered the consequences of a 1.5% industrial methane leakage and a CH4 global warming potential 72 times that of CO2 on a 20 year time scale and has concluded: “A complete consideration of all emissions from using natural gas seems likely to make natural gas far less attractive than oil and not significantly better than coal in terms of the consequences for global warming …Far better would be to rapidly move toward an economy based on renewable fuels. Recent studies indicate the U.S. and the world could rely 100% on such green energy sources within 20 years if we dedicate ourselves to that course. [10]” [11].

I have done simple calculations showing that a 3.7% leakage of CH4 and a CH4 GWP 72 times that of CO2 yields that same greenhouse gas effect as burning the 96.3% remaining CH4 i.e. a roughly doubled GHG emissions from gas burning [12].

However assessment of recent US EPA data indicates a methane leakage rate in the US of 3.3% [13, 14] and as outlined above the global warming potential of CH4 on a 20 year time scale is 105 relative to CO2 if the impact on global-dimming aerosols is included.

I have accordingly performed a re-calculation of GHG/energy in tonnes CO2-e/MWh based on these updated assessments as outlined below.

Methane (CH4) has a molecular weight of 16 and carbon dioxide (CO2) has a molecular weight of 44.

When you burn CH4 you get CO2: CH4 + 2O2 -> CO2 + 2 H2O.

Accordingly burning 16 tonnes of CH4 yields 44 tonnes of CO2 and burning 100 tonnes of CH4 yields 100x 44/16 = 275 tonnes of CO2.

However if there is industrial leakage of CH4 then one must consider the greenhouse gas effect of the released methane (105 times worse than CO2 as a greenhouse gas on a 20 year time scale).

Of our 100 tonnes of CH4, how much CH4 leakage (y tonnes) gives the same greenhouse effect (in CO2 equivalents or CO2-e) as burning the remaining CH4?

y tonnes CH4 x (105 tonnes CO2-e/tonne CH4) = (100-y) tonnes CH4 x (2.75 tonnes CO2-e/ tonne CH4).

105y tonnes CO2-e = (100-y) 2.75 tonnes CO2-e

105y = 275 – 2.75y

107.75y = 275

y = 275/107.75 = 2.55 tonnes i.e. a 2.6% leakage of CH4 yields that same greenhouse effect as burning the remaining 97.4% of the CH4.

This result has been checked thus:
2.55 tonnes leaked CH4 corresponds to 2.55 tonnes CH4 x 105 tonnes CO2-e/ tonne CH4 = 268 tonnes CO2-e . Burning the remaining 97.4 tonnes of CH4 corresponds to 97.4 tonnes CH4 x 2.75 tonnes CO2/tonne CH4 = 268 tonnes CO2.

What does this mean when we compare the greenhouse gas dirtiness of gas-burning or coal-burning for power? This question can be addressed by using data for gas-fired and coal-fired power stations in the major state of Victoria, Australia.

In Victoria, Australia, gas-fired power stations (0.60 – 0.90 tonnes CO2-e/MWh) are roughly twice as efficient in producing energy as brown coal-burning power stations (1.21-1.53 tonnes CO2-e/MWh) according to a report by Green Energy Markets commissioned by Environment Victoria (EV). This report offers 2 scenarios for replacement of the dirtiest coal-burning plant, brown coal-fired Hazelwood Power Station, with 62% gas (Scenario 1) and 33% (Scenario 2) in relation to total annual energy production (measured in MWh) and 96% gas (Scenario 1) and 75% gas (Scenario 2) in relation to peak summer power (measured in MW). [15].

If we assume that burning gas with no leakage gives an average of 0.75 tonnes CO2-e /MWh, what is the efficiency when methane leakage is factored in?

(A).At a leakage of 2.6% of industrial methane, the greenhouse gas (GHG) from leakage is the same as the GHG effect from burning methane to give CO2 i.e. the GHG/MWh ratio roughly doubles to 1.5 tonnes CO2-e/MWh, equivalent to that of one of the world’s dirtiest coal burning-based power plants, Hazelwood .in Victoria, Australia (1.53 tonnes CO2-e/MWh).

If we consider the dirtiest Victorian gas-fired power plants (0.9 tonnes CO2-e/MWh) the GHG/MWh ratio increases by a factor of 2/0.974 = 2.05 to 1.80 tonnes CO2-e/MWh, 20% dirtier than Hazelwood. (1.53 tonnes CO2/MWh). If we consider the cleanest Victorian gas-fired power plant (0.60 tonnes CO2-e/MWh) the GHG/MWh ratio increases to 2.05 x 0.6 = 1.23 tonnes CO2-e/MWh, 80% as dirty as Hazelwood. If we consider the average gas-fired plant (0.75 tonnes CO2-e/MWh) the GHG/MWh increases to 2.05 x 0.75 = 1.54 tonnes CO2-e/MWh, slightly more than for Hazelwood (1.53 CO2-e/MWh).

(B) At the current gas leakage rate in the US (3.3%) an overall consumption of 100 tonnes CH4 results in 3.3 tonnes leaked CH4 x 105 tonnes CO2-e/ tonne CH4 = 346.5 tonnes CO2-e (from gas leakage) plus 96.7 tonnes CH4 x 2.75 tonnes CO2-e/tonne CH4 burned = 265.9 tonnes CO2-e (from burning the remaining methane) = 612.4 tonnes CO2-e/100 tonnes CH4 i.e. the GHG/MWh ratio roughly increases by a factor of 612.4/(275.0 x 0.967) = 2.30.

The GHG/MWh in units of CO2-e/MWh for Victorian gas-fired power stations accordingly increases on this 3.3% leakage scenario to (a) 2.30 x 0.6 = 1.38 tonnes CO2-e/MWh (cleanest gas-fired power station; 90.2% of Hazelwood’s); (b) 2.30 x 0.75 = 1.73 tonnes CO2-e/MWh (average gas-fired power station; 113.1% of Hazelwood’s) and (c) 2.30 x 0.90 = 2.07 tonnes CO2-e/MWh (the dirtiest gas-fired power station; 135.3% of Hazelwood’s i.e. 35% dirtier than the coal-fired Hazelwood power plant, the dirtiest in Victoria).

Accordingly, these latest estimates of the Global Warming Potential (GWP) of methane relative to CO2 on a 20 year scale (105) and of methane leakage (3.3%) indicate that gas burning for power can be much dirtier greenhouse gas-wise (GHG-wise) than coal burning.

On these estimates a stationary energy sector transition from coal burning to gas burning to reduce GHG pollution is strongly contra-indicated. Gas burning for power can be much dirtier greenhouse gas-wise than coal burning.

Notwithstanding the science, the fossil fuel industry and allied lobbyists, commentators and politicians in the Western Lobbyocracies and Murdochracies continue to promulgate the falsehoods that “gas is clean energy” or that “gas is cleaner energy than coal”, most notoriously so in climate criminal Australia, a world leader in per capita greenhouse gas pollution, coal exports and liquid natural gas (LNG) exports. [16].

Decent people around the world must (a) inform everyone they can that gas is dirty energy, that gas burning for power can be much dirtier greenhouse gas-wise than coal burning and (b) must resolutely, through voting, sanctions and boycotts, eschew any avoidable dealings with countries, corporations, people and politicians involved in the worsening, terracidal Gas Boom, Gas Rush and global Gasland perversion.

[1]. Drew T. Shindell, Greg Faluvegi, Dorothy M. Koch, Gavin A. Schmidt, Nadine Unger and Susanne E. Bauer, “Improved Attribution of Climate Forcing to Emissions”, Science 30 October 2009:
Vol. 326 no. 5953 pp. 716-718: http://www.sciencemag.org/content/3... .

[2]. Shindell et al (2009), Fig.2: http://www.sciencemag.org/content/3... .

[3]. IPCC AR4, “Synthesis report summary for policy makers”, 2007: http://www.ipcc.ch/publications_and... .

[4]. [4]. Katharine Sanderson, “” Aerosols make methane more potent”, Nature News, 29 October 2009:http://www.nature.com/news/2009/091... .

[5]. Dr Drew Shindell, quoted in Mark Henderson, “Methane’s impact on global warming far higher than previously thought”, The Times, 30 October 2009: http://www.timesonline.co.uk/tol/ne... .

[6]. Robert Goodland and Jeff Anfang, “Livestock and climate change. What if the key actors in climate change are … cows, pigs and chickens?”, World Watch, November/December 2009: http://www.worldwatch.org/files/pdf... .

[7]. Professor Hans Joachim Schellnhuber, “Terra quasi-incognita: beyond the 2 degree C line”, < 4 Degrees & Beyond, International Climate Conference, 26-30 September 2009, Oxford University , UK : http://www.eci.ox.ac.uk/4degrees/pp... .

[8]. Dr Vicky Pope, “Met Office warn of “catastrophic” rise in temperature”, The Sunday Times, 19 December 2008: http://www.timesonline.co.uk/tol/ne... .

[9]. Kevin Anderson & Alice Bows, “Reframing the climate change challenge in light of post-2000 emission trends”, Proc. Trans. Roy. Soc, A, 2008: http://rsta.royalsocietypublishing.... .

[10]. Mark Z. Jacobson and Mark A. Delucchi, “A path to sustainable energy by 2030”, Scientific American, November 2009, pp 58 – 65: http://www.scientificamerican.com/a... .

[11]. Robert Howarth, “Preliminary assessment of the greenhouse gas emissions from natural gas obtained by hydraulic fracturing”, Cornell University, 1 April 2010: http://www.technologyreview.com/blo... .

[12]. Gideon Polya, “Gulf oil & gas disaster, lobbyists, Obama & huge threat of natural gas (methane) to Humanity & Biosphere”, Bellaciao, 19 June 2010: http://bellaciao.org/en/spip.php?ar... .

[13]. David Lewis, "EPA confirms natural gas leakage rates" (The Energy Collective, 7 December 2010: http://theenergycollective.com/inde... .

[14]. Gideon Polya, “Resource to stop gas-fired power plants, fossil fuel burning, GHG pollution & man-made climate change”, Bellaciao, 27 February 2011: http://bellaciao.org/en/spip.php?ar... .

[15]. Green Energy Markets, “Fast-tracking Victoria’s clean energy future to replace Hazelwood”, 2010: http://www.environmentvictoria.org.... .

[16]. Gideon Polya, “Gas is dirty energy & may be dirtier than coal - Oz Labor’s "gas is clean energy" means Put Labor Last”, Bellaciao, 10 June 2010: http://bellaciao.org/en/spip.php?ar... .

Forum posts

  • CORRECTION. The Global Warming Potential of methane (CH4) is 105 relative to that of an equal number of molecules (NOT an equal mass) of carbon dioxide (CO2) on a 20 year time scale and taking aerosol impacts into account. [1] This makes the gas versus coal situation even worse as the following calculations show.

    1 mole (16g) of methane (CH4) has 105 times the greenhouse gas (GHG) effect as 1 mole (44g) of carbon dioxide (CO2) and, accordingly, 1t leaked CH4 is equivalent to 105x44tCO2/16 = 288.8t CO2-equivalent.

    Burning 16t CH4 yields 44t CO2 and accordingly burning 1t CH4 yields 44/16 = 2.75t CO2. Burning 12t carbon (C; atomic weight 12) yields 44t CO2 and hence burning 1t C yields 44/12 = 3.7t CO2.

    Burning 100t CH4 (circa 85% of natural gas) yields 275t CO2 and about the same electrical power as burning 200t coal (C) which yields 200x3.7 = 740t CO2. However, based on the latest US EPA data the CH4 leakage in the US is 3.3% and hence using 100tCH4 for electrical power yields 1,218.9t CO2-equivalent.

    According to Professor Robert Howarth fugitive emissions from CH4 leakage are 1.7-6.0% for conventional gas and 3.6-7.9% for shale gas (e.g. from “fracking”) [2] and hence using 100t of conventional gas to generate electricity actually yields 761.3-1,991.3t CO2-equivalent and using shale gas actually yields 1,304.8-2,534.8t CO2-equivalent i.e. using gas for electrical power is much dirtier greenhouse gas-wise than burning coal.

    Accordingly, the Australian Labor Government ’s Carbon Tax-based coal to gas transition strategy for “tackling climate change” is utterly wrong and counterproductive - it increases rather than decreases GHG pollution.

    Some key references:

    [1]. Drew T. Shindell, Greg Faluvegi, Dorothy M. Koch, Gavin A. Schmidt, Nadine Unger and Susanne E. Bauer, “Improved Attribution of Climate Forcing to Emissions”, Science 30 October 2009: Vol. 326 no. 5953 pp. 716-718: http://www.sciencemag.org/content/3... .

    [2]. Robert W. Howarth, Renee Santoro, Anthony Ingraffen, “Methane and the greenhouse gas footprint of natural gas from shale formations”, Climatic Change, May 2011: http://www.sustainablefuture.cornel... .

    • Do you have any data on production of methane in black coal (or brown coal) mining? Methane liberation is known to occur in underground mines, but is it significant in the terms of its GHG effect?

      A true comparison between gas and coal in terms of GHG effect should take this into account.