A satellite monitoring technique that uses the reflection of the sun makes it possible to detect methane leaks from offshore oil rigs from space.
Methane is a potent greenhouse gas about 80 times more efficient than carbon dioxide at trapping heat. The amount of methane in the atmosphere has more than doubled since pre-industrial levels, largely from human sources like livestock, landfills and oil and gas production.
Along with airplanes and ground-based sensors, a growing constellation of satellites monitor methane plumes with infrared sensors. These sensors can detect even very small land-based methane plumes, but they can鈥檛 spot the gas when it is released over the ocean because the water absorbs too much infrared light.
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That leaves the amount of methane emitted by the offshore oil and gas industry largely unknown beyond the numbers that operators report themselves. Offshore facilities make up about 30 per cent of total oil and gas production.
at GHGSat, a Canadian satellite company, and his colleagues got around this problem by positioning a satellite at just the right time and angle to capture the glint of the sun on the water around the target, an approach known as 鈥済lint mode鈥�. At the glint spot, the water acts like a mirror to reflect enough sunlight onto the infrared sensor to identify the methane signal.
The researchers used this method to coming from an oil rig in the Gulf of Mexico in August at a rate of 1500 kilograms an hour, the smallest amount of methane from an offshore source yet detected from space. 鈥淲e鈥檙e pushing the limits of its capabilities for offshore measurements,鈥� says McKeever.
The only previous methane plume detected over the ocean from space was reported in June by at Valencia Polytechnic University in Spain and her colleagues. The team used glint spots captured incidentally in to detect a different oil rig in the Gulf of Mexico spewing methane at 100,000 kilograms an hour.
Such extremely large plumes make up a significant share of offshore methane emissions, but the smaller ones also add up, says Irakulis-Loitxate. The new detection 鈥渙pens up the opportunity to discover hundreds of previously hidden emission sources鈥�, she says.
at the University of Michigan says 1500 kilograms is still a large plume, and many smaller plumes might go undetected from space. His group鈥檚 of methane plumes from oil and gas platforms in the Gulf of Mexico found they released between 600 and 1700 kilograms per hour on average. McKeever says he expects the method can be improved further.
at Carbon Mapper, a research organisation in California, says monitoring more offshore methane emissions will require satellites making 鈥渞egular, sustained, wide area observations鈥�. Carbon Mapper is set to launch two methane-sensing satellites that can run in glint mode in 2023.
