Ever since the Environmental Defense Fund published a paper by Al Armendariz in 2009 alleging that emissions of volatile organic compounds (VOCs) from natural gas operations in the Barnett Shale are greater than VOCs from all the cars and trucks in the region, the statement has been repeated over and over as if it were fact (for example here). The paper and its conclusions were thoroughly disputed at the time and TCEQ’s analyses have never supported that claim.
In its 2011 State Implementation Plan (SIP), the TCEQ projected VOCs from oil and gas sites to be 113 tons per day (TPD) in 2012 (2011 SIP, page ES-1). The SIP also said that emissions from the 3 mobile sources--on-road mobile, non-road mobile and off-road mobile--were projected to contribute 129 tons per day of VOCs in 2012, which obviously is more than projected emissions from natural gas sites.
TCEQ’s most recent estimate of VOC emissions from oil and gas production in the Barnett Shale regions has been revised down to 63 TPD. The reduction is based on an equipment survey that TCEQ conducted in late 2011 where they found that the use of low bleed, ultra low bleed and no bleed pneumatic devices is more widespread than they had assumed. So, the fact is that TCEQ says that VOC emissions from Barnett Shale natural gas sites are less than half of the VOC emissions from non-oil and gas mobile sources.
It has also been alleged that VOC’s cause smog (for example here), or more precisely ground level ozone, in North Texas but that is not true either. Ground level ozone results when VOCs are combined with nitrogen oxides or NOx, which comes from the exhausts of cars, trucks, and non-road engines, such as bulldozers and other construction equipment, and then catalyzed by sunlight. By themselves, VOCs are not “smog-causing.” TCEQ emphasizes that NOx, not VOCs, drives the highest ozone levels in North Texas. Even if all man-made VOCs were eliminated in this region, there are more than enough naturally occurring VOCs from trees, plants and other organic sources to combine with NOx to cause smog.
Given the importance of NOx, it is important to note that TCEQ says that NOx emissions from non-oil and gas mobile sources are approximately 15 times higher than NOx emissions from oil and gas sources as a result of the lower NOx-emitting large engines that are used at gas compressor stations and other oil and gas and non-oil and gas sites in the Dallas-Fort Worth area.