A system of underground pipes collects gas at Miramar landfill, but not all of it. March 2016, Megan Wood, inewsource.
A system of underground pipes collects gas at Miramar landfill, but not all of it. March 2016, Megan Wood, inewsource.

For the first time, it’s possible to visualize where powerful, invisible methane gas hovers over the landscape of San Diego County.

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If we are to limit disruption from climate change, it’s essential to stop losing methane – which is also a valuable fuel – to the sky. That can’t happen without pinpointing and measuring escapes of gas.


Researchers have identified dozens of methane hotspots, including a series of hits near the Miramar landfill, with the gas apparently drifting to the end of the pier at La Jolla’s Scripps Institution of Oceanography, where a different group of scientists has an air intake connected to some of the world’s most sensitive atmospheric analyzers.

“Any time we go by Miramar from any direction, we pick up something,” said Chun-Ta Lai, a San Diego State University associate professor of biology who studies greenhouse gas emissions and led the research here. The higher methane levels continued along state Route 52.

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To see a full-screen version of the map above, click here.

The emerging sketch of the gas is important because escaped methane is a bad actor. It holds heat close to the Earth, warming the planet into a less hospitable place, though the concentrations are not toxic for people.

The research is a collaboration among researchers from San Diego State University, the University of California Irvine and the University of Utah. They drove specially equipped vans around each region, drawing in air and simultaneously analyzing it for methane.

Professor Chun-Ta Lai and teams from San Diego State University, University of California Irvine and the University of Utah drove vans with methane analyzers around their regions. The photo was taken in 2013, Chun-Ta Lai, SDSU.
Chun-Ta Lai, a biologist at San Diego State University, April 2016, family photo.

The levels near La Jolla were elevated, but even higher were levels of the gas found near the Otay landfill in Chula Vista, with a plume leading west.

The flow of air west from the landfills may surprise Southern Californians accustomed to a prevailing breeze from the ocean. But in the cool of the night, the scientists say, that familiar ocean breeze actually reverses. Later, after the sun rises, it reasserts itself.

When he was gathering his air samples in the Ford Transit Connect van, Lai drove most of his research runs at night, the time he said when the air is calm.

He shared the data, which has not been published, with inewsource, which produced an interactive map.

(Parallel research conducted by the UC Irvine team across the Los Angeles basin appeared in the Journal of Geophysical Research: Atmospheres in February.)

At Scripps Institution of Oceanography, which was not involved with Lai’s research, scientists also pick up “sources of methane quite near” the UCSD marine institution, said Ralph Keeling, a professor of geochemistry. “The highest values we see are when the wind is out of the east, and that points right at the Miramar landfill.”

There is no complete analysis at this point, he said. But “that is suspect No. 1.”

The landfill lies 6.1 miles from the pier, as the crow flies.

The methane Lai found is not likely to directly harm people. For the most part, it does not contain the foul-smelling chemicals that so bothered residents of Porter Ranch in Los Angeles County when a Southern California Gas well failed there recently, and the levels are too low.

The harm instead is to the environment, and possibly to San Diego’s ambitious Climate Action Plan. The plan commits the people of San Diego to reducing greenhouse gas emissions 60 percent below what would be predicted for 2035. It goes beyond the ambitions of most cities. San Diego’s plan aims for reductions on the order of what scientists say will actually be necessary to keep climate change in check. Plus it’s legally binding.

But it’s not at all clear that San Diego is accurately counting its methane emissions.

When landfills report methane to government agencies, they often use estimates, not actual measurements.

The Miramar landfill is the largest emitter of methane in San Diego County, by its own account. Because of that the city has no choice but to sharply reduce emissions there to meet milestones under its plan.

Yet city officials in charge of the landfill could not say how much methane is being released from it. They could not say who provided baseline figures about the landfill’s emissions to the drafters of the city climate plan. And they could not say by how much those emissions will be reduced to comply with the plan.

Ray Purtee, a senior mechanical engineer, said the city contracts with a company that measures methane near ground level four times a year, walking a serpentine pattern across 400 acres. The contractor looks for cracks where methane flows out and concentrates at higher than 500 parts methane per 1 million parts air. The contractor always finds such places.

“We might find 20 in one quarter, we might find 90 in a quarter,” Purtee said.

Records show the landfill and its related contractors have been cited numerous times by the San Diego County Air Pollution Control District for uncontrolled escapes of methane from underground where garbage is rotting, sometimes sending forth streams of gas through cracks at more than 2,000 parts per million, four times the legal limit.

Whether it’s the city, which owns the landfill, that finds the crack, or the county, which enforces air pollution laws, earthmovers then mound up soil on the bleeding cracks and the ground is remeasured.

Yet the search is for these leaking cracks, not for how much total climate-changing gas is escaping.

This lack of data has become something of a cause for Ray Weiss, who is also a geochemist at Scripps. From laboratories there, he monitors levels of methane measured at the end of the pier, along with dozens of other climate-changing gases from monitors around the globe.

“When we measure what appears in the atmosphere compared to what people say they are emitting, it is often quite different,” Weiss said.

Professors Ralph Keeling and Ray Weiss, both geochemists at Scripps Institution of Oceanography, March 2016, Megan Wood, inewsourc
Scripps Institution of Oceanography geochemists Ralph Keeling and Ray Weiss, March 2016, Megan Wood, inewsource.

“You don’t want to discourage somebody who is doing something important for the environment,” Weiss said, referring to the San Diego Climate Action Plan. “On the other hand, you want it to work, and the climate in the end doesn’t really care what we do politically, or what we say we are doing. It only cares what we actually do. So there is a real need for independent verification as we embark on reducing our greenhouse gas emissions.”

This is especially true for methane, because in the short term, it is 84 times worse for the atmosphere than carbon dioxide.

Some city officials maintain that, rather than being undercounted, methane is being over counted from Miramar. Methane gas forms as natural materials decompose in moisture and without oxygen. Mike Thompson, deputy director of the San Diego Environmental Services Department, said that just isn’t happening as fast as federal guidelines presuppose in dry Southern California.

“We just pulled up a Life magazine from 1958, and you could read the cover as clear as day,” he said.

But in places where sophisticated measurements of the air near landfills have been carried out, such as in Germany, they’ve found estimates are too low, sometimes by a factor of two.

The only way to eliminate the methane made vivid on the new map of Lai’s data, said Nick Lapis, is to stop throwing food and other live material in the garbage.

“There is no excuse in 2016 to landfill organic waste. We have better things to do with that material,” he said.

Lapis is the legislative coordinator for Californians Against Waste, an environmental advocacy organization. Those “better things” include grinding up the material into

compost. The state is slowly moving in that direction. Residents in the Bay Area have had curbside pickup of their food waste for several years. And a new law went into effect April 1 requiring California businesses such as restaurants that create a certain amount of food waste per week to have it picked up separately.

Nick Lapis is legislative coordinator with Californians Against Waste, which advocates for elimination of food waste and other organics from landfills as well as other pollution reduction measures. 2016, Nick Lapis.
Nick Lapis is legislative coordinator with Californians Against Waste, 2016, Nick Lapis.

“Landfill emissions are a really big deal,” Lapis said.

Exactly how big a deal locally will not be known until there is accurate measurement. Any system of comprehensive measurement is in its infancy, but even so, San Diego is behind.

Scripps scientists are part of a project planning team working to put 10 precision analyzers on the ground in the Los Angeles area and coordinate the measurements with aircraft and satellite data.

“I would very much like to see what we are doing in Los Angeles extended to San Diego,” Keeling said. “We are really part of one large urban area.”

Lai would also like to build on his initial drive-around research. He would like to find out just how much methane comes out of the sites he flagged with his analyzer. With the addition of an an infrared gun, he would be able to see the shape of the invisible plumes, and where they are coming from. “That would be awesome,” Lai said. But that work will have to wait. He’s out of funding.

Ingrid Lobet is a reporter at inewsource specializing in the environment. To contact her with tips, suggestions or corrections, please email ingridlobet@inewsource.org.

4 replies on “San Diego County’s methane problem visible for first time”

  1. No mention of why the methane capture system, all those plastic pipes over the landfill, isn’t working as designed?

  2. The first place they point a finger at is the landfill SIX miles away? My B.S. meter is going off!

    Have the researchers checked out the natural gas pipeline locations near where they are getting these high methane readings? After the Parker Ranch debacle, natural gas storage and distribution systems would be my first suspect.

  3. Thank you trashtsar – great handle – I think there were several arrows pointing in that direction, but you’re right, it’s not for sure. I think everyone is hoping there will be more followup, to better pinpoint the exact sources.

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