Title image: A technician inspects a high-tech laser at a natural gas facility in Colorado. (Credit: Casey Cass/CU 麻豆影院)
Sean Coburn walks down a dusty dirt road in Greeley, Colorado, flanked by a scene that鈥檚 becoming more common in this city at the edge of the Front Range鈥攔ows and rows of tanks, pipes, stacks and other hallmarks of the oil and gas industry.
The engineer, who earned his doctorate from CU 麻豆影院 and now splits time between the university and a company called , is wearing a flame retardant jacket, bulky boots and a hard hat. He needs them on this site. Here, operators take raw and very flammable oil and natural gas, the latter mostly composed of methane, and process it into a form that people can use to heat their homes or drive their cars.
But Coburn is heading for something else: a metal tower, about 50-feet-tall with what looks like a security camera on top.
鈥淲e pipe the laser light up from there,鈥� said Coburn, pointing at a cabinet at the base of the tower. 鈥淭hen we shoot it at different targets around the site.鈥�
As he talks, the cabinet beeps, and the laser emitter at its end begins to turn, sweeping over the landscape.
The tower is part of an ambitious undertaking from scientists at LongPath and CU 麻豆影院. They鈥檙e using new laser technology to do what other technologies have struggled to do for years: detect natural gas, which is invisible to the eye, leaking from pipes at sites like this, in real time.
Methane is a powerful greenhouse gas, said Greg Rieker, an associate professor of mechanical engineering听at CU 麻豆影院. He testified before the U.S. House of Representatives听Committee on Science, Space and Technology听June 8 . He noted that methane听can trap nearly 80 times more heat in the atmosphere than carbon dioxide, and research suggests that escaped methane from oil and gas operations may play a much bigger role in climate change than previously thought.
LongPath is trying to plug that source. The company鈥檚 towers shoot lasers over miles of terrain to sniff out even the faintest whiffs of methane in the air. So far, the company has installed 23 of them covering almost 300,000 acres in Texas, New Mexico, Oklahoma听and Colorado. Rieker believes听the technology could be a win-win for the West: Slowing down emissions of this dangerous gas, while also reducing costs for an industry that employs tens of thousands.
The story of this technology, called a dual frequency comb laser spectrometer, dates back to the 1990s when a听 first developed frequency comb lasers to explore the working of atoms鈥攁nd earned a Nobel Prize in the process.
鈥淣ow, we鈥檙e able to use those same ideas and, with just one of these systems, mitigate about 80 million cubic feet of methane emissions per year,鈥� said Rieker who co-founded LongPath in 2017.
A LongPath Technologies van visits a natural gas facility in Greeley. (Credit: Casey Cass/CU 麻豆影院)
Thinking small
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Scott Diddams was part of those early days of frequency comb lasers. He was a postdoctoral researcher working with Hall at between CU 麻豆影院 and the National Institute of Standards and Technology (NIST), to probe quantum physics鈥攐r the mysterious workings of very, very small things.
The researchers weren鈥檛 thinking about methane hovering over oil fields at the time. Instead, they used their lasers to measure how fast atoms tick. To make an atomic clock, Diddams explained, physicists first shine laser light at a cloud of atoms, giving them a kick so that they flip between different energy levels at a staccato pace. Hall鈥檚 group invented frequency combs to help count out that rhythm.
鈥淎toms tick nearly a quadrillion times per second,鈥� said Diddams, now a professor in the Department of Electrical, Computer and Energy Engineering. 鈥淵ou need a really special tool to count those cycles.鈥�
Frequency combs were special. Normal lasers, like the pointers in any lecture hall, can only generate one type of light: say, red light or green light. But these new lasers could produce thousands or even millions of colors of infrared light at the same time鈥攁n entire rainbow inside a single beam.
Hall and German scientist Theodor H盲nsch took home a Nobel in 2005 鈥渇or their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique."
By the time Rieker joined CU 麻豆影院 in 2013, he and Diddams were already wondering what else frequency combs could do.
Quantum comb
Greg Rieker (left) works with a colleague in his听lab at CU 麻豆影院. (Credit: Casey Cass/CU 麻豆影院)
Comb-like spikes on a computer听screen illustrate measurements of methane, water and carbon dioxide. (Credit: Casey Cass/CU 麻豆影院)
A laser emitter sits at the top of a tower at a natural gas facility in Colorado. (Credit: Casey Cass/CU 麻豆影院)
At LongPath鈥檚 offices in 麻豆影院, Coburn and his colleagues open a computer window showing the data coming in from the system in Greeley. The graph shows a squiggly readout with sharp spikes like the teeth in a comb.
Each tooth corresponds to a color in the team鈥檚 frequency comb laser (hence, the name). Rieker explained that if you shine one of these devices into a cloud of gas, the molecules inside will absorb some of those colors but not all of them. In other words, molecules will leave an imprint on the laser light, almost like pressing your thumb to a glass.
鈥淓ach of these different molecules absorbs a different pattern of light,鈥� Rieker said. 鈥淢ethane has one pattern. Water and carbon dioxide have another.鈥�
Frequency comb technology can read those molecular fingerprints to tell you exactly what kinds of molecules are present in a patch of air.
Or that was the theory in the mid-2000s. Rieker and scientists from NIST took roughly a decade to make it reality. First the team had to shrink these lasers, which could fill entire rooms, down to the size of a suitcase鈥攖hen design them to survive the extremes of Colorado winters.
鈥淲e tested what happened when our laser froze,鈥� Rieker said. 鈥淲e broke it every way we could think of breaking it.鈥�
Traditionally, he said, oil and gas operators look for leaks by using special video cameras or by hiring airplanes to fly overhead. Frequency comb lasers, in contrast, can operate 24/7 without a single human involved.
For 11 months in 2017 and 2018, the team put its technology to the test with funding from the U.S. Department of Energy. Rieker and his colleagues deployed one of their lasers at a natural gas storage facility in California. The laser, then mounted to the roof of a trailer, was able to detect methane leaks over several miles of terrain and at an incredible precision of just a few parts per billion. Because the system ran all the time, they were able to detect 12 times more methane per month on average than traditional tools spotted.
鈥淎fter that, it spread by word of mouth,鈥� Rieker said. 鈥淏ecause these things work.鈥�
From atoms to stars
Around the same time, Rieker co-founded LongPath Technologies with his then research scientists Coburn and Robbie Wright, and Caroline Alden, a research scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU 麻豆影院.
In the beginning, it was slow-going. To launch LongPath and secure initial funding, Rieker and his colleagues worked with Venture Partners, the university鈥檚 commercialization arm for campus researchers. The company鈥檚 first employees worked out of rented space in Rieker鈥檚 basement lab on campus.
鈥淚nstead of the startup-in-a-garage, we were the startup-in-a basement. Then when COVID hit we all were working out of our own basements,鈥� said Wright, now vice president of engineering at LongPath. 鈥淏ut in the past year we finally got our first dedicated office, and we鈥檝e scaled from having three deployments out with one customer to 23 deployments with 17 customers."
Oil and gas executives have come around to these lasers, in part because they can save companies money, Rieker added鈥攅ven a routine leak, he said, could cost operators thousands of dollars if they don鈥檛 catch it right away.
He鈥檚 now trying to replicate the success of LongPath.
In 2021, Rieker signed on to lead a new effort on campus called the Quantum Engineering Initiative, which seeks to transform other, fundamental scientific discoveries into real tools that you can hold in your hand. Graduate students in the engineer鈥檚 lab aren鈥檛 done with frequency comb lasers, either. This year, researchers will install one over a patch of frozen soil near Fairbanks, Alaska. They鈥檙e hoping to measure how much methane gas leaks out from that soil as it warms because of climate change.
Graduate student David Yun, meanwhile, uses frequency comb lasers for a completely different purpose: To study how hypersonic jet engines suck up and burn oxygen as they roar to life. Diddams employs a similar set of tools to search for planets circling stars tens of light-years from Earth.
鈥淲e really want to push the limits of where we can take this technology,鈥� Yun said. 鈥淲e keep pushing to see what is the craziest thing we can do with frequency combs?鈥�
For Rieker, it鈥檚 a testament to science coming full circle鈥攆rom explorations of atomic jitters to a Nobel Prize and even technology that may soon improve the lives of everyday Coloradans.
鈥淭his is a technology that was developed for something completely different鈥攆or creating better atomic clocks and other tools for quantum research,鈥� he said. 鈥淣ow, we鈥檙e making an impact on climate change.鈥�
As a global leader in climate, environmental and energy research, the 麻豆影院 is partnering with United Nations Human Rights to co-host the Right Here,听Right Now Global Climate Summit in fall 2022.听
