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Carbon Management – Is it me…thane?

Methane (CH4) is the main component of natural gas, however, methane emissions are rising and it is a potent, and the second most prevalent, Greenhouse Gas (GHG). 1 tonne of methane has the global warming potential of 25 tonnes of carbon dioxide (over a 100-year time horizon, including indirect effects of ozone and water vapor production). Current levels of methane in the atmosphere at 1.8 ppmv have doubled since pre-industrial times. So where do these GHG emissions come from? What is the contribution from livestock, wetlands, natural geologic seeps, and coal mines? While there are many natural and man-made sources of methane, the range of uncertainty in natural gas systems is considered the largest because of sparse activity data, large daily variations, numerous sources and limited measurements.

Natural gas offers many health and environmental benefits over other traditional fuels given it has low or zero emissions of the main air pollutants, including fine particulate matter (PM2.5), sulfur oxides (SOX), and nitrogen oxides (NOX). According to the International Energy Agency (IEA) 2016 special report on air pollution, coal use dominates global emissions of SO2, oil products used for transport are the dominant source of NOX, while the combustion of wood and other traditional solid fuels are responsible for more than half of current PM2.5 emissions.

The IEA also estimates that annual methane emissions from natural gas supply are 61 million tonnes (a GHG impact of 1,290 million tonnes of CO2-eq annually) and comprises 61% of total gas supply GHG emissions. For comparison, this is equivalent to annual transport related emissions in Europe, or all energy sector emissions in Canada and Germany combined. However, there is also uncertainty in the level of methane emissions that can occur – planned or unplanned – in the value chain from natural gas production to final commercial or residential customer. This uncertainty over the level of methane emissions, the vast majority of which is not measured but estimated, has been raising questions about the extent of the climate benefits that natural gas can bring.

Our analysis shows there is clear scope to reduce methane emissions cost-effectively; after all, natural gas has commercial value and keeping it within the supply chain means that additional methane captured can often be monetized directly and GHG emissions reductions can result in economic savings or be carried out at low cost.

When society compares the benefits of coal-to-gas switching it needs to consider both CO2 emissions of end-use combustion, along with the indirect emissions of CO2 and methane released during production, transport and processing. If the methane emission intensity of natural gas is below 5.5%, then gas has lower lifecycle GHG emissions than coal. These green credentials of natural gas can be confirmed. Are you confident in the accuracy of your methane emission numbers? Do you know the options and costs of reducing your methane emissions? There are many technologies available that can help monitor and manage methane emissions cost effectively to assure and ensure the benefits of natural gas in the global energy system continue.

Nigel Jenvey's picture

Thank Nigel for the Post!

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Bob Meinetz's picture
Bob Meinetz on Oct 6, 2019 2:46 pm GMT

What is the contribution from livestock, wetlands, natural geologic seeps, and coal mines?

Nigel, all in your list but livestock and coal mines have contributed methane to the atmosphere since long before Homo Sapiens existed. Over the course of a century or two methane naturally decomposes to CO2, and is reaborbed during plant photosynthesis. Then the cycle repeats. The current explosion of GHG concentrations can be blamed entirely on anthropogenic sources since 1850.

"Are you confident in the accuracy of your methane emission numbers? Do you know the options and costs of reducing your methane emissions?"

I think you ascribe too much social responsibility to people who burn fossil fuel for a living. With little monetary incentive to reduce them, why would owners of gas plants care a whit what their methane emission numbers are?

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