AIR QUALITY AND GREENHOUSE GAS IMPACTS FROM UNCONVENTIONAL NATURAL GAS DEVELOPMENT

Recent technological advances in horizontal drilling and hydraulic fracturing have led to the widespread use in attempts to access natural gas in shale formations despite uncertainties relating to the possible environmental impact. Unconventional natural gas (UNG) development activities generate a complex mixture of emissions that could potentially degrade local and regional air quality. Airborne pollutants such as methane (CH₄), carbon dioxide (CO₂), nitrogen oxides (NO_x), volatile organic compounds (VOCs) and particulate matter (PM) are all emitted from multiple point sources throughout the various stages of operation (well pad construction, vertical drilling, horizontal drilling, hydraulic fracturing, flowback, and production). Additional negative impacts to air quality can result from the reaction of VOCs and NOx to form ground-level ozone and particulate matter. The variability and complexity of these emissions make an unconventional shale gas development site difficult to characterize as an air pollutant source.

Research on local and regional air quality impacts of unconventional natural gas development at the National Energy Technology Laboratory (NETL) has focused on conducting multiple targeted on-site measurements of emissions from gas production activities using a trailer-based air monitoring laboratory. The temperature controlled laboratory contains several instruments that automatically collect continuous data (with one-minute to one-hour resolution) that can be accessed via satellite.

The data collected from the monitoring campaigns is used as input or to verify both atmospheric chemistry and transport models and life cycle assessments of natural gas development greenhouse gas emissions. These models help assess the impact that unconventional gas development activities have on local and regional air quality. Such improved evaluations facilitate more informed decision making for regulatory and permitting applications.