Life Cycle Assessment of Air Toxins for Natural Gas Production, Transport, and Power Generation in the Marcellus Shale Region

Fossil fuel power generation technologies offer a number of alternatives which involve different fuel supplies, production, power generation, and pollution control devices with varied environmental impacts. The holistic approach to examining these impacts through Life Cycle Assessment (LCA) can help decision-makers to quantify the many emissions trade-offs inherent in any change to the fuel supply and power production systems and ensure that a change in fuel or fuel sourcing does not result in increases of other environmental and health impacts. Besides endpoint emissions exiting from a smokestack in natural gas-fueled power generation, air toxics (such as formaldehyde, benzene and xylenes) are also generated through the supply chain from compressor engines and oil/condensate tanks, as well as intermittent sources such as well drilling and fracturing engines, well completions, gas processing, and also fugitive emissions from production and transmission. These emissions sources differ in quantity, species, spatially and in overall risk to the surrounding population. People exposed to air toxics at sufficient concentrations and durations may have an increased risk of developing cancer or experiencing other serious health effects. The purpose of this paper is to identify the appropriate air toxics emission factors for natural gas production and to utilize a LCA approach to quantify the "cradle-to-gate" air toxics emissions in terms of 1 kWh of electricity generated.