Sandia LabNews

Mobile facility measures greenhouse gases


SANDIA’S MOBILE GREENHOUSE GAS test facility, which consists of two moving van-sized trucks, each equipped with instrumentation and equipment, measures air quality during a test deployment at DOE’s Atmospheric Radiation Measurement facility in Oklahoma. (Photo by Hope Michelsen)

When funding became available for the NNSA labs to develop climate-change solutions, a number of researchers at Sandia put their collective heads together and agreed that a mobile facility — one that could be transported to various locations on an as-needed basis — would be a timely and useful contribution.

So that’s what they built.

 “What we proposed to do was build a mobile facility that would measure greenhouse gases and other species associated with those gases so they could be traced and identified,” says Hope Michelsen (8353), a combustion and atmospheric chemist and one of the lead researchers on the project.

In addition to pinpointing the chemicals’ location information, the idea behind the mobile facility is to learn whether the gases are biogenic (coming from plant sources) or anthropogenic (coming from man-made sources). This is important when officials look at ways to mitigate emission impacts in their communities, regions, states, or even nations.

 “Elected officials who have enacted new policies to help reduce unwanted greenhouse gas emissions could conceivably find a mobile facility to be of great use,” Hope says. “To figure out whether emissions reduction policies are effective, we need a way to measure emissions by emissions sector, such as power generation or transportation. We currently don’t have the tools in place to do these types of measurements, so we hope our idea can be part of the solution.”

The mobile system, which has already been deployed once to the Atmospheric Radiation Measurement (ARM) facility in Oklahoma, consists of two moving van-sized trucks, each equipped with instrumentation and equipment. Included are instruments that measure greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), and species co-emitted with greenhouse gases, such as sulfur dioxide (SO2), nitrogen oxide (NOx), carbon monoxide (CO), ozone (O3), and other traditional pollutants.

While the instruments are all commercially available, another current project funded internally at Sandia aims to build an instrument that measures black carbon soot, a devastating warming agent formed through the incomplete combustion of fossil fuels, biofuels, and biomass.

Distinguishing emission sources

Atop each truck sits an antennae-like mast that sucks in air, sends it down into the truck, and distributes it to the various instruments, including a mass spectrometer that sorts out hydrocarbons and helps to distinguish between emission sources, which can range from traffic to pine trees.

A piece of equipment provided by Lawrence Livermore National Laboratory (LLNL) captures samples in flasks for analysis at LLNL’s Center for Accelerator Mass Spectrometry to measure the radiocarbon (14C) fractionation of CO2 (14C is a radioactive isotope of carbon).

Because 14C is severely depleted in fossil fuels, it is a powerful indicator of man-made CO2 sources. Some of these samples were also sent to the National Oceanic and Atmospheric Administration and to the University of California, Davis for further trace gas and isotopic analysis.

The ARM location in Oklahoma, says researcher Ray Bambha (8128), was selected because of its solid history as a climate research site. Ray served as the principal investigator for the field experiment, alongside several other Sandians serving in key roles. Collaborators from both LLNL and Los Alamos National Laboratory joined the Sandia team for portions of the Oklahoma deployment.

‘Uncertainty quantification’ capability

The pilot deployment, Ray says, was successful in that the system collected large quantities of data, which is still being analyzed. It allowed the team to test instruments that hadn’t been used previously, and it helped them to understand the atmospheric community’s need for an “uncertainty quantification” capability — a method of assigning a confidence level to an estimate — and tracer measurements, which provide a more effective method for identifying the source of certain emissions.

Hope says Sandia is building a team of researchers that can take the next step with the system and begin to use wind information and inverse modeling to more accurately identify emission sources.

In the short-term, Hope says, program development efforts are well under way in hopes of securing follow-on funding and other test deployments. The long-term vision for the program calls for a full network of mobile facilities that could be deployed strategically in select regions, states, or cities to enable the capturing of a broad spectrum of emissions and related information.