Ryan Maye Handy

The Coloradoan

Boulder scientists measuring greenhouse gas levels over the Denver-Julesburg basin have found triple the amount of methane floating over Weld County than government estimates show.

Most of the methane is coming from oil and gas operations within the county, which in 2012 had 24,000 wells scattered across its prairies, according to a study released Wednesday by the University of Colorado Boulder and National Oceanic and Atmospheric Administration.

Methane is a powerful greenhouse gas with 21 times the impact of carbon dioxide on climate change, according to the study. It is also a common byproduct of oil and gas operations, which release methane in relatively unknown quantities.

Using an airborne measuring device during two days of testing in May 2012, the Boulder scientists measured methane levels in the atmosphere. Their study found that oil and gas operations over the Denver-Julesburg basin in northeastern Colorado produced about 19 metric tons of methane per hour, three times the amount reported in the Environmental Protection Agency's Greenhouse Gas Reporting Program.

"These discrepancies are substantial," Gabrielle Petron, the study's lead author, said in a written statement. "Emission estimates or 'inventories' are the primary tool that policy makers and regulators use to evaluate air quality and climate impacts of various sources, including oil and gas sources. If they're off, it's important to know."

According to the study, levels of benzene and volatile organic compounds were also higher than government estimates.

As potent as methane is, it's a natural element in Weld County. Natural gas, one of the main commodities being extracted from the shale formations in Northern Colorado, is 90 percent methane, said Ken Carlson, an associate professor of civil and environmental engineering at Colorado State University.

There are a half a million head of cattle in Weld; the manure they produce is also a source of methane. The coal seams in Weld County, formed millions of years ago, also contain methane.

Until recently, the amount of methane being released by oil and gas operations has been difficult to track, and it is likely not limited to one part of the extraction and production process, said Carlson. The Boulder study is one of many over the years that has tried to pin down the amount of methane emissions and where they come from — the study estimates 75 percent of Weld County commissions come from oil and gas development.

With the support of its three largest oil and gas operators — Anadarko, Encana and Noble Energy — Colorado recently approved new air quality standards meant to tackle and limit methane emissions. The standards should go into full effect by the end of the year. The regulations were heralded as the first of their kind in the nation, Carlson said.

While the Boulder study's findings are significant, Carlson said they were not exhaustive when it comes to studying how methane emissions can be limited.

"It certainly shouldn't be discounted," Carlson said of the study on Wednesday. "It seems like this issue is more complicated than a two-day flyover."

"We need more data," he added.

Since last spring, a group of CSU researchers have pursued that task — gathering data on methane emissions from all aspects of the oil and gas production process, said Dan Zimmerle, a scientist working on the project. The researchers are running two of five studies commissioned by the Environmental Defense Fund, which they expect to release in six to eight months.

Zimmerle couldn't discuss the preliminary findings of the study due to confidentiality agreements, nor could he discuss the methods being used, although he said they are different from those used in the Boulder study.

The CSU study is "the first really major update to methane emissions" from the Colorado oil and gas industry since 1996, Zimmerle said.

"As for where we think it will be used? Hopefully by the industry to improve their reduced emissions," he said.

At a glance

A study by University of Colorado Boulder and National Oceanic and Atmospheric Administration scientists found levels of methane, benzene and volatile organic compounds exceeded government estimates during two days of measurements in May 2012. The findings of emissions from oil and gas activities:

• Methane: 19 metric tons per hour (three times the estimate)

• Benzene: 380 pounds per hour (estimated at 50 pounds)

• Volatile organic compounds: 25 metric tons per hour (estimated at 13.1 tons)