Scrubbing VOCs Out of the DFW Ozone Problem

(NOTE ON GRAPHICS: Pie chart on the right  hand side is from 2012 estimates from the Texas Commission on Environmental Quality as part of the DFW State Implmentation Plan submitted to EPA in December 2011. Pie chart on the left hand side is from the Texas Commission on Environmental Quality for 2009 and still being used by the state)

Since DFW was first identified has having a smog problem in the mid to late 1980's, there's a standard formula that's become familiar to folks in local air quality: NOx and VOCs + Sunlight = Ozone.

There have always been two primary culprits to North Texas' chronic smog problem. NOx, or Nitrogen Oxides which primarily come from combustion sources (engines, boilers, furnaces), and VOCs, or Volatile Organic Compounds that are mostly invisible plumes and fumes from things like gasoline pumps, storage tanks, as well as combustion. These pollutants combine with sunlight and heat that chemically interacts with them and forms ozone downwind.

When the first air pollution control measures were adopted, Austin and the EPA agreed that VOCS were the driving force DFW ozone levels. Some old-timers may remember the Mrs. Baird's bakery on the West Freeway in Ft. Worth having to install controls that eliminated the smell of baking bread that was stout enough to waft across the highway. That's also why every gas pump in Collin, Denton, Dallas, and Tarrant Counties has a "Vapor Recovery Unit."

Over the years, the blame shifted to a combination of VOCs and NOx, and that's what made it possible to bring large NOx polluters like cement plants and coal plants into the picture. Still, VOC emissions remained a major player in the DFW smog problem, and they've been addressed with controls on everything from solvents, to boat resins, to bakeries by every single clean air plan ever drafted by the state and EPA.

But now Austin is saying VOCs aren't such a big problem after all, that DFW's smog is all about the NOx. Why? Austin's computer model says so. This is the same computer model that says DFW ozone levels will reach historic lows this summer. But might there be another reason? TCEQ's de-emphasis on VOCs coincides precisely with a very large jump in VOC pollution from the gas industry, a jump due to the explosion of drilling in the Barnett Shale and the government's lack of regulation to control it. In 2006, cars and trucks in DFW still spewed more VOCs than the gas industry. This year, the gas industry will release 30 MORE TONS PER DAY of VOCs than all the cars and trucks in DFW combined according to the TCEQ itself. But you'd never know it from looking at any of the public material the TCEQ produces about DFW's ozone problem. Instead it's all NOx all the time.

This slant benefits a politicized TCEQ in a couple of ways. First, when you talk about NOx, you don't have to talk about the doubling of gas industry emissions over the past decade or so. Second, you can keep repeating the mantra that it's all about cars. Cars only produce about 15% of the VOC pollution in DFW vs 49% of all NOx in North Texas. No need to worry about new controls on cement plants or coal plants when it's really all about cars. Until today, that TCEQ message creep was showing up locally in websites and promotional material sponsored by the North Central Texas Council of Governments (NCTCOG) made up of area municipal and county governments. 

Unlike in past years when the familiar formula of both NOx and VOcs was recited to the public, this year NCTCOG's Air North Texas site, Air Facts page trumpeted that "On road vehicles cause half of the ozone forming emissions. Ozone forms when nitrogen oxides (NOx) combine with sunlight and intense heat." That just wasn't true. When you combine all VOC and NOx emissions (as calculated by TCEQ) in DFW, on-road vehicles account for 29% of ALL ozone forming emissions. Point Sources like cement plants and other industrial facilities, combined with oil and gas sources, total 25% – a much different looking pie chart than when you use NOx emission alone.

To its credit, as a result of our inquiry, the NCTCOG Air North Texas "air facts" page has been re-edited to put VOCs back into the equation as of today, along with a little bit of spin claiming that "historical emphasis has indicated NOx reductions are the most appropriate way the region can lower ozone levels." We label that spin because it relies totally on the TCEQ's point of view, which has been, how do we put it, "historically wrong." We've already discussed how the DFW smog problem began as just a VOCs problem. We know they're still a factor. And if NOx reductions alone are so darn effective, why haven't they worked better? According to the TCEQ, total NOx pollution from ALL DFW sources decreased by almost 150 tons per day over the last six years. And yet 2011 was the worst ozone season since 2007. VOC Pollution? It's increased by 17 tons per day despite almost every individual category going down, save the ambiguous "Area" sources and emissions from the Oil and Gas industry.

So if NOx decreases ozone so much more effectively than VOC decreases, how come 2011 ozone levels didn't reflect that? Many public officials around the country cite scientific evidence that already smoggy air turbocharges the ability of gas patch pollution to create more ozone. Usually very weak VOC molecules are transformed into smog-producing machines. TCEQ refuses to factor in this scientifically validated increased reactivity of VOCs being released by gas sources despite predominate winds carrying already smoggy air into the heart of drilling country in Tarrant, Denton, Wise, and Johnson Counties. It's model doesn't recognize this phenomena happening. 

TCEQ may also be underestimating the ability of these weak VOCs to already make ozone. In her 2011 landmark "Leaking Money" report for Downwinders, Dr. Melanie Sattler wrote that just the sheer volume of new gas industry VOCs is enough to affect DFW ozone levels.

If DFW is ever going to solve its chronic smog problem, it has to have reliable information about what the increase in gas industry pollution is doing to our air. We don't have that now and no one in Austin is interested in finding out. Local leaders would be wise to decouple themselves from the TCEQ's politicized and uncurious approach to DFW air quality planning in Austin and find funding for their own research that can test for things the state doesn't want to know….

Here's the full statement of Chris Klaus, Senior program Manager at NCTCOG and the lead staff person ther for all things air: "We appreciate your e-mail and comments regarding air quality facts and information on our Air North Texas and the North Central Texas Council of Governments’ (NCTCOG) websites.  We welcome and value this type of input.  In regards to your comments, historical emphasis has indicated NOx reductions are the most appropriate way the region can lower ozone levels.  Of the primary emission sources, on-road vehicle activities account for nearly half of the NOx inventory.  We frequently discuss NOx and VOCs when providing outreach, and have updated the Air North Texas website to make sure VOCs are referenced when appropriate.  Air North Texas is meant for the general public, and NCTCOG staff feels it is more effective to educate them about what they can do to improve air quality, and how to protect their health and the environment."