https://www.abc.net.au/news/2020-11-03/fact-check-is-gas-just-as-dirty-as-coal-adam-bandt/12838066
The claim
Scott Morrison's plan for a gas-led economic recovery has brought the Coalition's climate and energy policies back into focus.
But the emphasis on natural gas — a fossil fuel mostly made up of methane — has alarmed some scientists and political figures, who say such an approach would only add to the challenge of tackling climate change.
In a September 23 tweet, Greens leader Adam Bandt said coal and gas must be kept in the ground "to have any chance of stopping runaway global warming".
"Gas is as dirty as coal," Mr Bandt said.
The verdict
Mr Bandt's claim is oversimplified.
The methane contained in natural gas is significantly more potent than carbon dioxide in terms of its impact in warming the atmosphere.
However, the debate in Australia has primarily focused on using gas to generate power, particularly to back up — or "firm" — intermittent renewable energy.
For electricity generation, gas is, on average, less emissions-intensive than coal, even after factoring in "fugitive emissions" lost in the transportation of gas, as well as other "upstream" and "downstream" sources of emissions linked to power generation.
How much less depends on the type of technology used.
Fact Check analysed 2018-19 emissions data for 82 gas and coal-fired plants.
On average, and weighted by the volume of power generated, gas generators were found to be significantly less emissions intensive than those fired by coal.
This was the case across various different types of power generation technologies.
The averages, however, masked significant variations in the performance of individual plants.
For example, Australia's "dirtiest" gas plant, Barcaldine in central Queensland, produces almost double the emissions per kilowatt hour of electricity generated than Australia's dirtiest brown-coal fired plant, Victoria's Yallourn power station.
In other words, gas is not always cleaner than coal for power generation.
Moreover, the analysis is clouded by scientific uncertainty relating to fugitive (and deliberately released) emissions linked to the extraction, processing, storage and transportation of gas.
Background to the claim
The debate about natural gas is not new. In February 2020, Chief Scientist Alan Finkel gave an address to the National Press Club in which he argued "natural gas will play a critical role" in helping the economy transition to lower greenhouse gas emissions.
And, in a subsequent appearance on the ABC's Q&A program in May, Dr Finkel said the fastest way to develop electricity from renewable sources was to back it up with gas which, unlike coal, can be switched on as needed.
"Gas has much, much more scale than batteries and gas is effectively the perfect complement to solar and wind," he said.
"We can build a lot of solar and a lot of wind, and use gas for times when we don't have the sun shining and the wind blowing to deliver the energy we need."
But those arguments have not been well received by some members of the scientific community.
In a letter sent to Dr Finkel in August, 25 Australian scientists argued that "there is no role for an expansion of the gas industry", claiming that such a commitment to gas was not consistent with a safe climate or the objectives of the Paris Agreement.
"The combustion of natural gas is now the fastest growing source of carbon dioxide to the atmosphere, the most important greenhouse gas driving climate change," they wrote.
In a written response published on his website, Dr Finkel said the adoption of more electricity sourced from renewables would be faster, more economical and more reliable if natural gas-fired electricity generation continued to be available in the near-to-medium term.
"Emissions from using natural gas to generate electricity are significantly lower than when using coal to produce the same amount of electricity, even when upstream fugitive emissions of methane are included in the analysis," Dr Finkel argued.
The idea that gas is necessary to back up intermittent renewable energy has been embraced by the Morrison Government.
In a September 15 speech delivered in the Hunter Valley, Mr Morrison outlined his plans for a gas-led economic recovery.
He said the electricity market needed an extra 1,000 megawatts of "dispatchable capacity" by the summer of 2023-24 to ensure affordable, reliable power, with final investment decisions by the end of April 2021.
Mr Morrison promised the Government would step in "and fill the gap'' by building a gas generator in the Hunter Valley should energy companies fail to provide that extra capacity.
Mr Bandt's claim was tweeted in response to a September 23 report published in The Guardian shortly after Mr Morrison's speech, which revealed federal Labor's new policy platform also backs the "responsible" and "environmentally sustainable" development of gas.
Where does Australia's gas come from and how is it used?
Australia produced 5,498 petajoules of natural gas in 2018-19, according to the Department of Industry, Science, Energy and Resources, with roughly three-quarters classified as "conventional" and one quarter "coal seam".
A further 202 petajoules was imported, with 14 petajoules netted off as "discrepancies" and "stocks". That created a total supply of 5,686 petajoules.
Of this, 72 per cent was exported, with the remaining 28 per cent used in Australia.
About 36 per cent of Australia's domestically consumed gas was used for electricity generation (including by LNG plants themselves), 23 per cent for manufacturing, 11 per cent for domestic use such as heating and cooking, and 30 per cent for a range of other purposes, including "own use" by LNG plants.
Testing the claim: what do we mean by 'dirty'?
In his tweet, Mr Bandt refers to a "climate emergency", stating that "toxic" methane is up to 86 times more potent for the climate than carbon dioxide.
Given the context surrounding and leading up to Mr Bandt's claim, Fact Check will consider the question of whether gas is "as dirty" as coal against the backdrop of the climate change debate, bearing in mind fossil fuel use can be "dirty" in other ways; for example, by creating localised pollution.
The question of whether gas is as dirty as coal is a complex one, even when limited to greenhouse gas emissions.
It can be considered in terms of the warming impact that gas (specifically methane) has on the atmosphere, compared with coal (specifically carbon dioxide).
Alternatively, the "emissions intensity" of gas versus coal for power generation can be examined.
As discussed above, power generation is the single biggest use for gas, and the main use for which coal and gas are directly comparable, as well as the focus of political debate in Australia.
However, comparing emissions intensity is not straightforward.
The emissions intensity of both coal-fired and gas power plants varies significantly, depending on the technology used and the size and the age of the facilities, among other things.
Open-cycle gas plants are used for "peaking" electricity, because they can be switched on at relatively short notice, meeting any potential shortfalls in supply.
On the other hand, as Dr Finkel has noted, combined-cycle gas power plants are more directly comparable to coal-fired plants, as both are required to run for longer hours, providing base-load power.
The Federal Government's Clean Energy Regulator publishes annual data estimating the emissions intensity of Australian power generation facilities, measured in tonnes of carbon dioxide equivalent per megawatt hour of electricity (TCO2-e/MWH).
It provides estimates for what it calls "scope 1" and "scope 2" emissions.
As the Clean Energy Regulator explains, scope 1 emissions occur "as a direct result of an activity, or series of activities at a facility level".
This includes emissions from burning a fossil fuel at a power plant to produce electricity, as well as on-site fugitive emissions, such as the release of methane during coal mining carried out adjacent to power stations.
Scope 2 emissions include emissions attributable to a facility, but which were produced at another facility; for example, emissions resulting from power drawn from the grid (produced elsewhere) that is used to run a coal-fired power plant.
The Clean Energy Regulator does not provide estimates of "scope 3" emissions. These are emissions that "occur as a consequence of the activities of a facility, but from sources not owned or controlled by that facility's business".
That includes any emissions resulting from off-site transportation, processing and storage.
This is particularly relevant to gas, which is processed and stored at terminals, and transported using pipelines and ships.
Gas extraction can also involve the release of significant amounts of carbon dioxide.
For this analysis, Fact Check used estimates for the scope 3 emissions intensity of individual power stations compiled by economic consultancy firm ACIL Allen for the Australian Energy Market Operator.
In Australia and elsewhere, there has been significant debate about fugitive (and deliberately released) emissions linked to gas extraction, processing, storage and transportation.
An October 2016 study conducted by the Melbourne Energy Institute, at the University of Melbourne, warned there was "significant uncertainty" surrounding estimates for methane emissions from gas production, with "no comprehensive, rigorous, independently verifiable audit of gas emissions".
Fact Check calculated weighted average emissions intensities for different power plants using the amount of power generated as a proportion of total power generated by various generation technologies.
For example, relatively small power stations were given a smaller weight, commensurate with their share of the total.
Impact on the atmosphere: gas versus coal
Both coal and gas are fossil fuels. Burning them releases greenhouse gases into the atmosphere.
But the greenhouse gases they contain are not the same, and do not have the same impact on the Earth's atmosphere.
Natural gas is predominantly methane, whereas coal emits carbon dioxide when combusted.
To compare the impact of different gases on the atmosphere, climate scientists often refer to "global warming potentials".
This measures how much warming a particular gas will cause over a particular period, relative to carbon dioxide.
As far as greenhouse gases go, methane is relatively potent, trapping heat in the atmosphere much more efficiently than carbon dioxide. How potent depends on the timeframe being applied.
Methane — the gas referred to by Mr Bandt — tends to break down relatively quickly (in about 12 years) compared to carbon dioxide, which can stay in the atmosphere for thousands of years.
Consequently, the "potency", or global warming potential, of methane depends greatly on the timeframe applied.
Australia, in line with long-established international practice, tends to apply a 100-year time frame.
For many years, Australia relied upon an outdated estimate of the global warming potential of methane based on the Fourth Assessment Report of Climate Science issued in 2007 by the UN's Intergovernmental Panel on Climate Change (IPCC).
However, the Government recently acknowledged the findings of the IPCC's Fifth Assessment Report, published in 2013. It found methane, in fact, to be 28 times more potent than carbon dioxide.
In June this year, Energy Minister Angus Taylor introduced laws to reflect the IPCC's 2013 finding, to apply from the 2020-21 financial year.
The 100-year timeframe is to some extent arbitrary. This is acknowledged by the IPCC.
"There is no scientific argument for selecting 100 years compared with other choices," it says.
"The choice of time horizon is a value judgement because it depends on the relative weight assigned to effects at different times."
The figure referred to by Mr Bandt in his tweet — that methane is up to 86 times more potent than carbon dioxide for the climate — is consistent with analyses over a 20-year timeframe, as outlined by the IPCC.
If we view the question of whether methane is more "dirty" than coal in terms of the impact on the atmosphere, then methane is clearly more potent as a greenhouse gas. How much more potent depends on the timeframe specified.
Is gas more "dirty" for power generation?
Mr Bandt made his claim following Mr Morrison's announcement of a "gas-led" economic recovery in response to the recession triggered by COVID-19, and Labor's reported endorsement of "environmentally sustainable" gas development.
Another way to analyse Mr Bandt's claim is to examine whether power generated using gas is more "dirty" than power generated using coal.
There is, however, a large variance in emissions between power plants, depending on the technology used, the age of the plant and its size, among other things.
Fact Check examined the emissions of 82 Australian gas and coal-fired power plants. The following table provides estimates of the volume-weighted average emissions intensity for different gas and coal-fired power generation technology for the 2018-19 financial year.
On a volume-weighted basis, gas is less emissions-intensive than coal. This is the case for open-cycle gas turbines, which can be switched on rapidly to provide peaking power, and combined-cycle turbines, which are less flexible.
Fact Check estimated that open-cycle (peaking) gas turbines produce 28 per cent less emissions per kilowatt hour of electricity than conventional (subcritical) black coal plants, 20 per cent less than high-efficiency (supercritical) black coal plants, and 45 per cent less than brown coal plants.
Combined-cycle gas turbines are less flexible than open-cycle plants, but they tend to be efficient and are more comparable to baseload-producing coal plants.
They produce a volume weighted average of 46 per cent less emissions per kilowatt hour than subcritical coal plants, 40 per cent less than supercritical coal plants and 58 per cent less than brown coal-fired plants.
However, the worst gas power plants, including the combined-cycle Barcaldine Power Plant in central Queensland, are still more greenhouse gas intensive than even the worst coal-fired power stations, including Victoria's brown coal Yallourn plant.
On the other hand, the most efficient supercritical coal-fired power stations, such as the Kogan Creek plant on Queensland's Darling Downs, are still significantly more emissions intensive than the most efficient combined-cycle gas plants.
As Dr Finkel pointed out in an email to Fact Check, electricity generated using combined-cycle gas turbines is a more relevant comparison to coal-fired electricity "because it is intended to run longer hours".
He said open-cycle gas turbines were used for peaking generation "so the total emissions per year are small and in any event it doesn't run for many hours in the year."
What the experts say
Hugh Saddler, an associate professor at the Crawford School of Public Policy and a research associate at the Centre for Climate Economics and Policy, said the question of whether gas was just as dirty as coal depended partly on the question of how much gas leaked into the atmosphere during the extraction and transformation of gas.
"I've not ever seen any data which suggests leakage from wells or pipelines or processing is large enough to offset the advantage that gas has compared to coal when it is burned," he told Fact Check.
But Associate Professor Saddler said it was difficult to get accurate measurements, with there being a lack of scientific work to measure leakage into the atmosphere in an Australian context.
Climate Council senior researcher Tim Baxter said many gas-fired power stations performed better than coal, "but some certainly do not".
"There are gas-fired power stations in operation today that are worse than many coal-fired stations even if you only consider emissions that occur at the point of combustion," he said.
Mr Baxter said gas produced more emissions per unit of energy during extraction, processing and transport.
Dr Finkel referred Fact Check to the findings of the Scientific Inquiry into Hydraulic Fracturing that was commissioned by the Northern Territory Government.
It's final report found "the best gas-fired generation [combined-cycle gas turbines, CCGT] is approximately 60 per cent as emission intensive as the most efficient coal-fired plant (ultra-supercritical coal HELE generation) based on life cycle [greenhouse gas emissions]".
"Even including upstream emissions, gas is in all cases cleaner than coal," Dr Finkel told Fact Check in his email.
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