Small hole in paddock responsible for 10,000 cars worth of emissions
The abandoned coal exploration borehole was drilled many years ago in a paddock in rural Queensland.
(Photo credit: The University of Queensland. )
Key points
- A single abandoned coal borehole in Queensland was found to emit as much methane annually as 10,000 cars.
- Researchers from The University of Queensland used advanced gas detection technology to determine 235 tonnes of methane were released per year from the borehole.
- With an estimated 130,000 similar boreholes across Queensland, sealing high-emitting sites could offer a cost-effective way to reduce emissons.
Researchers have found a single coal borehole in rural Queensland is releasing the same amount of greenhouse gases as 10,000 cars, revealing a potentially underreported source of methane in the atmosphere.
University of Queensland Gas & Energy Transition Research Centre researchers Associate Professor Phil Hayes and Dr Sebastian Hoerning took emissions readings over a week at a farm in the Surat Basin in central southern Queensland.
“This was the first long term measurement of methane emissions from an abandoned coal exploration borehole,” Dr Hayes said.
“This borehole is one of an estimated 130,000 in Queensland where the quality of sealing by coal explorers is unknown.”
Video: A legacy coal exploration hole lifting water and methane to the surface. The hole has since been sealed.
Dr Hayes said although it looks like a patch of bare ground in a cattle paddock, the borehole qualified as a methane super-emitter.
“We measured it to be releasing 235 tonnes of the greenhouse gas into the atmosphere each year,” he said.
“In terms of climate impact, that’s on par with emissions from 10,000 new cars driving 12,000 kilometres each, every year.”
Dr Hoerning said that there were thousands of abandoned coal holes and it was not known how well they are sealed – if at all – or how much methane they may be emitting
“While the majority of these boreholes won’t be emitters, our measurements show they could be a major source of greenhouse gas emissions that is currently unreported,” Dr Hoerning said.
The portable Quantum Gas LiDAR system, towed on a trailer, more accurately captured emissions that vary over time than common measurement methods such as handheld sensors.
(Photo credit: The University of Queensland.)
The researchers took emission readings using a portable Quantum Gas LiDAR system, which more accurately captures emissions that vary over time than the current common measurement methods such as handheld sensors.
Measuring emissions over a week allowed the researchers to see how emissions varied with temperature and different weather conditions, then that result could be extrapolated to give a weekly reading.
Dr Hayes said more surveys will likely reveal further opportunities for reducing Queensland’s greenhouse gas contributions by sealing old boreholes with the highest emissions.
“Our research has revealed a problem, but also an opportunity,” Dr Hayes said.
“Sealing the worst offending boreholes represents a straightforward and cost-effective way to quickly reduce greenhouse gas emissions.”
Dr Hayes and Dr Hoerning hope to expand their study to a larger sample of coal exploration holes to understand the frequency and rate of emissions, along with other emission drivers like geology and groundwater.
“The issue may also not be limited to coal boreholes, and we would be interested to study the emissions potential of water bores,” Dr Hayes said.
“We hope our work can eventually help reduce overall greenhouse gas emissions across Queensland and beyond.”
The research is published in Science of the Total Environment.
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