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Mar 19, 2012

Coal Seam Gas and fugitive emissions



A disused CSG well on a property near Dalby.

Coal Seam Gas and fugitive emissions

At the point of combustion, natural gas is the least dirty fossil fuel of all; not only does it produce more heat per kilogram of CO2 produced than any other fossil fuel, power stations burning gas use that heat more efficiently.   Electricity generated using a modern combined-cycle gas-fired power plant results in the emission of roughly one-third less CO2 than even a modern coal-fired power station.  For this reason, there are many who view natural gas as a “transition fuel” between our current coal-fired global economy, and a future driven by renewable energy.

Recent research, however, casts doubt on this rosy picture.  Anti-CSG activist group Lock the Gate points to recent research that suggests that gas from unconventional sources, including CSG, may actually have a bigger climate impact than coal.  The culprit?  Fugitive emissions – the gas that escapes into the atmosphere during the process of extraction, transport and processing.

In absolute terms, the amount of gas involved in fugitive emissions pales into insignificance compared to the CO2 released at combustion.  The problem is that the unburned coal seam gas that is released is a far more potent greenhouse gas than CO2 – but how much more potent is a complex question.

A problem of equivalence

As noted in my earlier article, the vast majority of unburned natural gas is made up of methane. Like CO2, methane is a greenhouse gas, acting as a blanket to trap some of the heat escaping from the Earth’s surface.  Methane is an even more effective blanket than CO2 – but it’s not a long-lived one.   Natural processes covert methane in the atmosphere to carbon dioxide and water over a timespan of less than a decade, on average.   Carbon dioxide added to the atmosphere is far more persistent; according to a widely cited scientific paper by Archer et al, it will take centuries, even millennia, for the atmosphere to reach its previous state when a large amount of extra CO2 is added.

To simplify comparison, scientists have estimated the relative “global warming potential” of different greenhouse gases over 20 and 100-year periods.  Over a 100-year period, the IPCC’s estimate is that methane has 25 times the impact on temperature as carbon dioxide – and most of that is over that first few years.  Over a shorter 20-year period, it has about 72 times the impact.

In an ideal world, we’d stop artificially releasing both methane and CO2 into the atmosphere immediately.  But, given that’s not going to happen, we need to prioritize mitigation activities, and the relative priority of CO2 and methane emissions reduction depends a great deal on the time period you think most important.

The Kyoto Protocol, and most of the carbon price schemes introduced around the world, use the 100-year potentials as their basis.   This justified on the basis that climate change is a long-term problem – which it is.  But it is also an increasingly short-term problem.  The IPCC’s Summary For policymakers of the projected effects  of climate change noted  that “…by 2020, significant loss of biodiversity is projected to occur in some ecologically rich sites, including the Great Barrier Reef and Queensland Wet Tropics”.  2020 is eight years from now.  Given the increasingly short timescale in which potentially disastrous consequences (of which these local examples are merely indicative) may occur, it may well make sense to prioritize methane emissions more highly than we presently do.

How much methane?

According to the environmental impact statements of CSG companies, not very much at all.  Santos’s GLNG project’s EIS, for instance, uses a “conservative estimate” that 0.1% of the well’s total production will escape as fugitive emissions.  The vast majority of “process emissions” will be “flared” – burned on site when it can’t be captured for sale, and most of that at the LNG compression facility.  But, even allowing for the additional global warming potential of methane, the contribution from fugitive emissions is miniscule, and the contribution of flaring very small compared to the greenhouse impact of the final usage of the gas in homes, factories, or gas-fired power stations.

However, there is next to no publicly-available, independent evidence to support this contention.  There are no independent, publicly available studies of fugitive emissions for coal seam gas in Australia – or anywhere else in the world.  Climate activist group Beyond Zero Emissions claims that the board of Worley Parsons, an engineering consultancy with substantial contracts with CSG companies, suppressed a report BZE commissioned which indicates that emissions are far higher than previously acknowledged by the CSG industry.   Worley Parsons was also commissioned by the industry body APPEA to analyse CSG emissions; the reportbases its estimate of fugitive emissions on environmental impact statements rather than any independent analysis.

Even so, the limited relevant evidence in the public domain available, from unconventional gas projects in the United States, such as “tight gas” and shale gas, suggest far higher fugitive emission rates than the 0.1% of the GLNG EIS.

American Studies

An analysis by three Cornell University academics compiled information from a variety of sources, including industry and the US EPA to estimate fugitive emissions from shale and tight gas.  One large source of fugitive emissions was after fracking, when methane-laden water comes back out of the well, and “drill-out”, when “the plugs set to separate fracturing stages are drilled out to release gas for production”.  Based on the reports, they “conservatively” estimated that 1.6% of the well’s total production could be released as fugitive emissions from “flow-back”, and another 0.3% from “drill-out”.  Losses during operation would be anywhere between 0.3% and 1.9% of total production.  Losses during transport and distribution were estimated to be of a similar magnitude.  However, it should be noted that losses away from the wells are not specific to CSG; they are a broader issue with any use of natural gas.   In any case, the academics, led by Robert W. Howarth, claimed that these high levels of fugitive emissions, and the use of what they view as more appropriate shorter-period warming potentials, that natural gas use from unconventional gas formations has a greater effect on climate than coal!

Their paper attracted a prompt rebuttal from another group of Cornell-based engineers, led by Lawrence Cathles.  The rebuttal ranges over a variety of topics, including debates about the relevant global warming potential.   But perhaps most important for the CSG discussion is the level of emissions during completion and operation.  Cathles et al claim that Howarth’s estimates of gas levels during well completion are too high, and that this gas could be captured (thus eliminating the emissions) or flared (thus radically reducing their impact on climate).  As the rebuttal notes, one of Howarth’s  key sources for the flow-back estimate was a presentation of technology to capture that methane – the technology was estimated to reduce fugitive emissions by 90%, making a large amount of valuable gas available for sale.

Howarth has published a rebuttal to the rebuttal, and the debate remains unresolved, and perhaps unresolvable without more information.  But additional evidence is accumulating.  Late in February, an  empirical study by was published by a team led by Gabrielle Pétron at the University of Colorado. This study involved directly collecting air quality data in the region of unconventional “tight gas” fields in that state.  Their data, while having wide uncertainties, suggests that somewhere between 2.2 and 7% of the methane extracted is lost.

It is important to note that one of the largest sources of fugitive emissions identified in the Howarth paper – the aftermath of the fracking process – is only relevant to a fraction of all CSG wells developed in Australia.  The Senate Rural Affairs and Transport reference committee’s interim report on the effects of CSG on the Murray-Darling Basin states that “…perhaps 30% – 40% of wells in the current developments” will undergo fracking or some other form of flow enhancement.”

Australian estimates

In principle, Australia’s CSG producers have an incentive to minimize fugitive emissions, over and above the value of the lost gas.  The carbon pricing package that passed Australia’s federal parliament with such fanfare in 2011 includes fugitive emissions from mining.  Like other “emissions-intensive trade-exposed” industries, they will receive a large amount of free permits; however, the incentives at the margin to reduce emissions remain strong.   However, such incentives are only effective if those fugitive emissions are accurately accounted for – and the recent research puts this in doubt.

While carbon pricing is yet to begin, Australia has been collecting detailed greenhouse emissions data since 1990 through the National Greenhouse Accounts, and private companies are required to measure their emissions under the National Greenhouse and Energy Reporting Act 2007.  The permitted methodologies are detailed in theNational Greenhouse and Energy Reporting (Measurement) Determination 2008, a government regulation.  The methodology for fugitive emissions reporting for the natural gas sector is based on a 2004 technical document by the American Petroleum Institute – using the same kinds of methods leading to the underestimate of emissions reported in the Petron study.   Neither document (as best as I can understand it) has anything specific to say about measurement or estimation methods for the aftermath of fracking – a potentially serious omission if the estimates of Howarth et al are reasonable.

If there is private data that supports the CSG industry’s position, it is not in the federal government’s hands.  On questioning by Senator Christine Milne of the Greens  in a Senate Estimates hearing, a representative of the Department of Climate Change stated that the current reporting methods were supported by a report by George Wilkenfeld and Associates.  However, as an earlier response to a question by Milne to Senator Penny Wong makes clear, Wilkenfeld’s report was an analysis of NGERS data, not an independent data-collection exercise – and, at least as of August 2011, they had not commissioned any independent assessments of CSG methane emissions.

The Senate Rural Affairs and Transport Committee’s report, while nominally about the impact on the Murray-Darling, also canvassed this topic.  Their report, noting the concerns, stated that accurate measurements relating to specific gas fields are required, with regulators having the technical capacity and an inspectorate capable of ensuring compliance.

In the Senate Estimates committee hearings with Senator Milne, the Department of Climate Change and Energy Efficiency representative mentioned that a “new approach” for assessing fugitive emissions which is “much more site specific” is under development.  It remains to be seen whether this “new approach” involves any independent, comprehensive assessment of actual emissions.

Too many unknowns

None of these issues appear intractable.  The gases possibly vented during fracking seem to be feasible to capture, or at worst flare – though it is possible that some ventings may occur away from the main well.  The other sources of fugitive emissions are essentially leaks, which appear to be rectifiable if they are detected – though the cost of such improved procedures, if required, is an open question.    But, as the Senate committee makes clear, a research and monitoring regime is required that is capable of determining whether fugitive emissions levels are actually as low as is claimed by the CSG companies – and ensures that they stay that way over the entire operation of the mines and beyond.

Otherwise, the environmental credentials of the industry, and its social licence to operate as a less damaging alternative to coal, are no better than conjecture.

*Dr Robert Merkel is a Lecturer in Software Engineering at Monash University. Read more about FAQ Research authors here.

Photo credit: Pandora Karavan. See more photo-essays here.


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