While year/year methane emissions and volatile organic compounds (VOC) from unconventional natural gas well sites and midstream facilities in Pennsylvania increased in 2015, several other pollutants dropped considerably, according to the state Department of Environmental Protection’s (DEP) latest air emissions inventory.
Methane emissions from industry operations increased by 4% from 2014 to 112,128 tons. VOCs were up 8% during the same time to 6,410 tons. The increases were mainly related to a growing number of sources. There were 10,287 well sites that reported in 2015, compared to 10,010 the prior year. The latest inventory lists 534 midstream facilities, compared to 508 in 2014.
Nitrogen oxides declined 6%, particulate matter was down 22% and sulfur oxides dropped 32%, as operators employed best practices more widely, DEP said. That’s an improvement from the period between 2013 and 2014 when emissions were up across all the categories. Year/year unconventional natural gas production also increased from 4.1 Tcf in 2014 to 4.6 Tcf in 2015.
The air inventory includes emissions from unconventional natural gas wells and processing operations, as well as compressor stations that receive gas from coalbed methane (CBM), conventional and unconventional sites. The industry must report emissions to the DEP under state law. DEP started collecting the data from unconventional sources in 2011 and later expanded those requirements to include midstream operations involving CBM sources and legacy producers.
Reporting sources include drilling rigs, wellheads, compressors and fugitive sources such as flanges, pumps and valves, among other things.
Although methane emissions increased, the average emission per facility stayed relatively flat in 2015. Average methane reported from each midstream compressor station decreased from 106.9 tons in 2012 to 97.5 tons in 2015. The average emission per well site was 8.3 tons in 2012 and 5.8 tons in 2015.
The DEP has proposed a new general permit for unconventional well sites and revisions for the general permit for natural gas compressor facilities. The changes are aimed at reducing methane emissions and minimizing other environmental impacts. A public comment period ended in June and the agency is still working on its proposal.