Satellites: a game-changer for methane leak detection?
While using satellite imagery to quantify methane leaks from landfill sites, PhD student Emily Dowd made a remarkable discovery.
When she studied the satellite images in greater detail, she noticed an enormous methane leak. With the help of GHGSat, a greenhouse gas emissions monitoring service, she was able to accurately trace the leak to a section of gas pipework, owned and maintained by Wales and West Utilities in Cheltenham.
Dowd, who is a researcher at Leeds University’s School of Earth and Environment and the National Centre for Earth Observation, was immediately curious. The leak was the largest methane leak she had ever seen in the UK. To put it in context, it was so vast it could it be seen from space.
But before she could act, Dowd needed to be sure that her findings were correct. After working with GHGSat, which carried out additional satellite studies, and the UK Met office, the University of Leeds contacted Dr James France. Using a hybrid vehicle, Dr France, a researcher at Royal Holloway University, who specialises in ground-based mobile greenhouse gas surveys, travelled to Cheltenham to verify Dowd’s findings.
France recalls, “We drove downwind of the site on two separate days. During that time, we measured very large enhancements of methane. Our laser absorption spectrometers have an accuracy of 1 ppb of methane. That is an extremely low detection rate. But the methane plume was so dense that we would have been able to measure without such precise instrumentation.”
During the observation period, Dowd says that the satellite-derived fluxes “varied from 236-1357 kg per hour” while the mobile measurement derived fluxes “were between 886-996 kg per hour.”
Dowd estimates a mean emissions rate of 754 kg/h, over 11 weeks. “The gas would have leaked a total of 1,393,392 kg of CH4” (around 1,400 tons).
Given that the global warming potential of methane is 84 times higher than of CO2, Dowd says that “by UK standards, this was a very large escape of methane.”
Levelling the playing field
While Dowd’s findings are extraordinary, they are also being seen by some energy experts as a profound game-changer for the industry. Data taken from satellite imagery has levelled the playing field.
“Now,” she says “anyone can detect, track and monitor methane leaks, and not just energy companies.”
Dr Jane Hodgkinson, an expert in sensor technologies at Cranfield University, opines, “This means that petrochemical companies operating in countries where regulations are less stringent may decide to make their operations cleaner as they know that the world is watching them.”
Having previously worked for Advantica, Dr Hodgkinson, who joined Cranfield University from the natural gas industry nearly two decades ago, adds: “Satellites provide enhanced detection and are likely in the future to be used by government agencies and well-resourced environmental campaign groups to ensure greater transparency and compliance.”
Dowd agrees with Hodgkinson that it is a significant moment “as it means that gas leaks are no longer being hidden behind closed doors, improving the transparency of unplanned leaks”. That said, Dowd prefers to take a more optimistic view. She says, “The aim of GHGSat is to work with the energy sector as a partner and not to call operators out. If gas producers are onboard, it is easier to find mitigation solutions.”
But according to Dr France, and Dr Hodgkinson, while hugely beneficial, satellite technology has its limitations. Says Dr France, “The downside of this type of satellite technology is that those operating it have to know exactly where to look because the viewing area is not very large, approximately 12km2. This is excellent for established sites where monitoring is known to be required, but it is probably not cost effective in attempting to find unknown or unlikely locations of emissions. Another disadvantage is the weather. If it is cloudy, then it can be difficult to source readings. Thirdly, as satellites revolve around the earth, depending on the orbital pattern, scientists may be limited to only periodic measurements.”
However, Dr Aidan Farrow, a senior scientist in air pollution at Greenpeace Research Laboratories and the University of Exeter, has identified a far greater weakness in satellite technology as a tool for methane emissions monitoring. He says. “… Emissions of gases like methane that are large enough to be detected from space are only part of the picture – most are too small to be detected in this way and therefore cannot be properly quantified…”
It is a view shared not only by other scientists, but by many responsible operators in the petrochemical sector, who not only have a duty of care to their staff and the local communities close to where their operations are located, but are also bound by strict regulations.
The European Union is set to introduce top-down quantitative measurements for all methane-handling infrastructure by the end of this year. To comply, petrochemical facilities in the EU will need to be able to measure the total emissions generated by their plant.
The problem says Dr Hodgkinson, is that “often petrochemical plants are located on large industrial sites. The challenge they might have is accurately identifying which plant, or which part of a plant, is emitting which gas, in order to fix the leak. Satellite imagery won’t tell you that. It will only provide you with the big picture.”
To provide that micro emissions picture, traditionally plants have relied on Optical Gas Imaging technology (OGI). But while the technology is effective, it has a blind-spot. Dr Hodgkinson explains, “When the gas that you want to detect, and the background temperature you want to image it against are at the same temperature, then it is not possible to detect a gas leak.”
Remote sensing technology
This is a major technology flaw not lost on Peter Schmitz, an HSEQ Manager, who works on one of Europe’s largest industrial sites.
Schmitz, who is the HSEQ manager for Fibrant B.V., a large chemicals company, which is located on the Chemelot Industrial Park in the Netherlands, says, “For a site like ours, which is situated next to a major population centre, we cannot rely on OGI sensors. In order to keep our people safe and the local community too, we use advanced Fourier transform infrared spectroscopy (FTIR) remote sensing technology, which gives us 24/7, 365 days a year detection and monitoring capability.”
It is state-of-the-art technology like this, which is supplied by Grandperspective GmbH, a Berlin-based company, that Schmitz thinks is the future of gas emission monitoring solutions.
The technology which combines a super-strength surveillance camera and the analytical power of a laboratory spectrometer, analyses radiation in the same way finger-print detection technology identifies an individual.
“This means,” says Schmitz, “that for the first time, we can not only identify a multitude of different chemicals, but pinpoint exactly where they are and the quantity of gas in the air.”
Schmitz says that Fibrant could install a raft of OGI cameras that would provide it with real-time visibility. “But, as high-tech as those cameras are, they are not able to distinguish reliably between methane and water vapour. Nor are they always able to accurately detect and quantify more hazardous materials such as ethylene and ammonia. So, they are just not fit for 24/7 monitoring purposes. In contrast, we only need one remote sensor equipped with FTIR spectroscopy, to deliver highly accurate measurements over distances of up to a kilometre.”
Before choosing to invest in next-generation gas leak technology, Schmitz and his team conducted robust and rigorous field trials, which have empirically proven that the sensors can not only detect gas leaks at ground level, but also those which are out of the range of conventional ground-based sensors.
Schmitz says, “This technology is a game-changer for the chemical industry. Unlike traditional sensor systems, FTIR spectroscopy, which identifies the source of a leak, while accurately measuring the duration and the total loss, will enable much more precise and immediate monitoring than is conventionally possible.”
So, will pioneering technologies such as FTIR Spectroscopy replace legacy technologies in petrochemical plants in the future? Dr France said that “while there is great value in instrumentation that can detect multiple gases in complex environments, especially when attributing and quantifying top-down measurements, individual uses cases, different scenarios and different gas detection regulation, will dictate which technology is best utilised.”
This, he says, means that no one technology will dominate. “There is no one-size-fits-all solution. OGI sensors certainly won’t disappear. I also expect laser spectroscopy to be in great demand.”
Schmitz, however, has already made up his mind. “Conventional gas monitoring systems are not able to respond in the same time frame, or as precisely as FTIR spectroscopy systems,” he says. “They are too good a system not to use.”