Are coal companies underreporting methane emissions?

Aattention is focused on Australia’s new path to a 43% reduction in greenhouse gases by 2030, controversy has erupted over how to measure methane.

Although we produce less methane overall, it is a more potent greenhouse gas than carbon dioxide because it has a much higher heat trapping capacity. On a weight basis, methane has more than 20 times the global warming potential of carbon dioxide.

There are two ways to measure emissions of methane and other greenhouse gases.

There’s the traditional “bottom-up” method, where the data comes from modeling and sampling – usually reported by those who emit. The other is the “top-down” approach, where satellites observe and record levels of methane or other pollution in the atmosphere above certain locations.

Depending on who you ask, either of these methods is unreliable. The controversy is at the center of a claim that the Hail Creek mine, about 80 kilometers south-west of Mackay in Queensland’s Bowen Basin, is emitting 10 times more methane than it tells authorities.

To understand this, let’s start with how bottom-up reports work.

To control our emissions, we first need to know how much we actually produce. Creating an “inventory” of our emissions may seem simple, but it can be quite difficult to do.

According to CSIRO, in Australia, sources of such emissions information include livestock population counts, population data from the Bureau of Statistics and national reports on greenhouse gas emissions and energy from companies. oil and gas.

On a weight basis, methane has more than 20 times the global warming potential of carbon dioxide.

Collecting this data is a good start, but it’s not foolproof. While there are rules in place to ensure the numbers are as correct as possible, they are routinely lower than top-down reviews of the shows suggest.

According to research published in Science in 2018, oil and gas emissions were underestimated by the United States Environmental Protection Agency by about 60%.

This has important implications for how much we reduce our carbon emissions over the next few years to be able to limit the worst effects of climate change.

Methane (CH4) is a particular problem. It is the second most abundant greenhouse gas in our atmosphere after carbon dioxide (CO2), and it’s 25 times more powerful at trapping heat, although it doesn’t last as long in the atmosphere. It comes from sources such as wetlands, cow burps and mining.

Gases like methane can escape from coal seams during coal mining – if this is not noted in the upward emissions it is called “leakage”. In coal mines, methane and other gases are usually released by degassing or ventilation systems. The gases are a byproduct of the coal formation process – where organic matter, in the absence of oxygen, is heated and compressed over time. Some coal regions may be particularly rich in methane.

Stopping methane emissions would go a long way in limiting the climate crisis, but we really need to know how much is being released into the atmosphere.

To control our emissions, we first need to know how much we actually produce.

This is where the top-down approach comes in. Instead of relying on source-reported methane emissions, new satellites like the Copernicus Sentinel-5 Precursor can monitor the atmosphere and show in fairly high resolution – each pixel covers 7 x 5.5 km2 – from which polluting gases such as ozone and methane escape. This allows researchers not only to measure an entire country’s methane, but also to measure gases released from local areas such as mines.

“Satellite observations of methane are rapidly improving in terms of precision and spatial resolution,” says Dr. Cathy Trudinger, senior researcher in atmospheric chemistry at CSIRO.

“Use TROPOMI [the TROPOspheric Monitoring Instrument that’s aboard the Sentinel 5 satellite] it is possible to tell if a single mine or wetland has very large emissions, but the new satellites allow even more detail to be seen, allowing more precise quantification and estimation of smaller emission sources. This is an area that is developing very rapidly. »

The problem is that these top-down satellite surveys consistently show far more methane and other greenhouse gases than the bottom-up approach.

These top-down satellite surveys consistently show significantly more methane and other greenhouse gases than the bottom-up approach.

This brings us to the Hail Creek mine. In 2021, researchers from the SRON Netherlands Institute for Space Research published an article in the journal Environmental sciences and technologies. They found that in 2018 and 2019 the mine leaked somewhere in the realm of 230,000 tonnes of methane, which is much higher than the mine’s bottom-up report.

“Focusing on individual sources, our estimate for Hail Creek is more than 35 times higher than reconstructed bottom-up emissions and 15% higher than reported methane emissions from all surface mines in the State of Queensland combined,” write the researchers in their article.

Satellite images are striking, showing pixelated bright red clouds over Bowen Basin. Even more striking – if true – is the suggestion that just Hail Creek is responsible for more methane emissions than the entire state of Queensland reports for its mines.

The researchers also examined two other plumes spotted in the area. One is from the Broadmeadow, Moranbah North and Grosvenor underground mines, while the other is from the Grasstree and Oaky North underground mines.

But 40% of quantified emissions in the entire study came from a single open pit mine – Hail Creek.

Glencore – a major international mining company that owns the Hail Creek mine – dismissed the findings, suggesting the research contains inaccurate information.

“The SRON document provided limited information or detail on the emissions estimation methodology they applied,” they wrote in a press release. “Atmospheric contaminants such as dust, water vapor or smoke can impact the accuracy and validity of TROPOMI instrument measurements.

“The document also failed to acknowledge that there were no pre-drainage or underground mining activities at the Hail Creek open pit at the time of the study.”

Of course, that’s science, and we can’t be 100% sure, at least not yet.

But independent researchers are pretty confident it’s likely methane emissions, not aerosols like dust or smoke or problems with albedo – a measure of light reflection from Earth that the satellite uses to get a result.

“The plumes in Figure 1 appear to move with the wind, so this would likely rule out albedo issues due to fixed characteristics like soil type,” says CSIRO’s Trudinger.

“I couldn’t quite say how accurate they are… [but] the results seem likely to me and would certainly warrant further investigation.

Dr Nicholas Deutscher – a University of Wollongong scientist whose work specializes in validating satellites with ground-based measurements (including TROPOMI) – agrees.

“There’s enough corroborating evidence out there to make me think they found the sources,” he says. “In terms of the quality of the quantization, I think they’ve actually done a pretty rigorous job of it. And there are several things that make me think they may even have erred on the side of caution.

Of course, that’s science, and we can’t be 100% sure, at least not yet.

“What we really need is to independently verify these results by another method.”

Dr Nicolas Deutscher

Deutscher suggests using ground measurements to double-check the validity of the results.

“What we really need is to independently verify these results by another method,” he says. “So go out in the field and do measurements in that plume near the surface, or do our kind of ground measurements that validate satellite measurements over that range.”

It’s not just a problem in Hail Creek. While we have pretty good estimates of methane emissions globally and emissions nationally from top-down satellite data, we are only now seeing a more accurate picture of which mines appear to be underreporting.

“CSIRO conducted a top-down study with two monitoring stations in coal gas producing gas from Surat in Queensland and found that methane emissions were 33% higher than inventory in this region,” says Trudinger.

This is also partly due to the way monitoring works. Government oversight requires companies to provide these reports which can easily miss emissions like methane leaks. For example, you can measure the amount of coal you burn multiplied by the amount of methane produced per piece of coal, with sampling to verify your operation. However, as top-down satellite measurements suggest, that doesn’t quite capture all the detail.

“It’s not necessarily harmful. It also depends on the reporting requirements,” says Deutscher. “It is really difficult to quantify these different emissions because they change in space and time.

“That’s the fundamental problem with bottom-up estimates, you make a lot of assumptions about whether this process is the same all the time or just perfectly linearly dependent.

“It’s not always the case.”

“That’s the fundamental problem with bottom-up estimates, you make a lot of assumptions about whether this process is the same all the time or just perfectly linearly dependent.”

Dr Nicholas Deutscher

Unfortunately, to our knowledge, there does not appear to be an easy way to limit these methane emissions without shutting down the entire mine.

“If coal mining companies continue to argue that managing fugitive methane is too difficult for surface coal mines, then the obvious and material solution is to stop opening new mines,” Naomi Hogan, head of mining strategic projects with Australasian Center for Corporate Responsibility Inc, says Bloomburg. “And for known high-gassing mines to seriously consider early closure options.”

Although Glencore announced that it would reduce its emissions by 15% by 2026 and 50% by 2035, it did not respond to weekly cosmos‘s questions about how it will play out. It should be noted that a Guardian investigation in 2019 revealed that Glencore had funded a coordinated campaign to support coal and send an anti-renewables message.

In the meantime, broadcast satellites zooming in on these coal mines are giving us more data.

Deutscher believes so – and newspapers like that of Environmental science and technology – will encourage mining companies to clean up their reporting law.

“They can come out and deny it, but you can bet behind the scenes they’re there doing everything they can to make sure it’s not real,” he says.

Comments are closed.