Air Quality Implications of Future Scenarios for Oil and Natural Gas Production and Use in the Western United States

Nsanzineza, Rene

Graduate Thesis Or Dissertation

Air Quality Implications of Future Scenarios for Oil and Natural Gas Production and Use in the Western United States Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/wd375w51q

Abstract

Since 2005, electricity generation in the United States has shifted from coal to increasing reliance on natural gas power plants and renewable sources while the production of oil and gas has increased to satisfy the increased demand. This shift in the energy landscape has air quality implications for local and regional air quality in the U.S., especially in the Rocky Mountain (RM) region which has abundant supplies of oil and gas and a large share of electricity generation from coal. This study aims to examine the prospective impacts of energy shifts in this region on electricity generation, emissions, ozone, and human health from 2011 to 2030. We focus on the RM region since it has several areas facing challenges to meet the National Ambient Air Quality Standard (NAAQS) for ozone.

This study builds up on a previous study by McLeod et al. (2014) who applied the MARKAL (MARKet ALlocation) model and EPA’s 9-region U.S. energy system database to investigate several future scenarios, finding the least cost means of satisfying demand for energy in each scenario and the associated annual emissions in the U.S. and the RM region out to the year 2050. We adapted four scenarios from McLeod et al.’s study. The baseline scenario assumes a supply and prices of natural gas based on reference projections made in 2013 while the greenhouse gas (GHG) fees scenario assumes a supply of natural gas similar to the baseline scenario but applies fees to the emissions of CO₂ and CH₄. Two contrasting scenarios are the cheap gas scenario which assumes a high supply of natural gas at lower prices while the costly gas scenario assumes a low supply of natural gas at higher prices.

We downscale emissions from electricity generation temporally and spatially to capture the effects of changes in the small-scale emissions on the local and regional air quality. The electricity generation mix is estimated using the PLEXOS dispatch model on an hourly basis for a one-year period. The estimated generation from coal and natural gas power plants in each scenario is combined with unit specific emissions rates to determine the future emissions from power plants. Annual oil and gas production in the RM region are downscaled to the basin level to determine basin specific scaling factors used to estimate future emissions scenarios from oil and gas production.

The estimated emissions from power plants and oil and gas production as well as emissions from other energy sectors are processed with the SMOKE software package and then incorporated into the CAMx chemistry and transport model to determine the change in ozone associated with changes in emissions in the different scenarios. A health benefits analysis tool, BenMAP-CE, is used with the ozone modeling results to determine the human health impacts and their monetary value associated with the change in ozone.

We find that electricity production in the western U.S. from coal and natural gas increases from 2011 to 2030 along with generation from renewable energy as electricity demand increases from population growth. Contrary, to the trend in generation, NOx emissions from electricity production decrease by 33% over the same period as a result of retirement of old inefficient coal-fired plants, power plant refueling, and emissions control application. Within the western U.S, electricity generation and emissions vary by state and time of the year. Oil and gas production increases from 2011 to 2030 corresponding to increased demand, hence NOx and VOC emissions from oil and gas production increase by 5% and 58%, respectively, despite the emissions reductions from regulations imposed on the oil and gas sector. The net tradeoffs in these emissions trends lead to reductions in the summer MDA8 ozone as high as 8 ppb from 2011 to 2030, especially downwind of power plants and oil and gas basins in the 4 km CAMx domain. However, elevated ozone persists in urban areas such as Denver and Salt Lake City during peak time periods. The reduction in ozone from 2011 to 2030 is estimated to result in 303 to 360 reductions in premature deaths per year in the 4 km CAMx domain, in addition to reductions of morbidities associated with ozone.

Between scenarios, electricity generation from natural gas displaces some coal generation in the cheap gas scenario compared to the 2030 baseline scenario, while renewable energy capacity expansion, particularly wind energy, displaces generation from coal and natural gas in the costly gas and the GHG fees scenarios. A similar trend is observed in the oil and gas production with production increasing in the cheap gas scenario and decreasing in the costly gas and the GHG fees scenarios. In the western U.S, total annual NOx emissions from electricity generation decrease in all scenarios from the baseline scenario by 7% to 40% while NOx emissions from oil and gas production increase 27% in the cheap gas scenario and decrease 21% and 16% in the costly gas and the GHG fees scenarios, respectively. Changes in the annual total VOC emissions are a 37% increase with the cheap gas scenario and reductions of 25% and 22% in the costly gas and GHG fees scenarios, respectively. For the 4 km CAMx domain, these trends in emissions lead to a modest overall spring and summer MDA8 ozone increase from the baseline to the cheap gas scenario with a maximum increase of 1.5 ppb. In contrast, ozone decreases from the baseline to the GHG fees scenario, with a maximum decrease in MDA8 ozone of 2 ppb. Correspondingly, health effects benefits are estimated from the GHG fees scenario with premature deaths decreasing by 27 to 32 per year compared to the 2030 baseline. The cheap gas scenario offsets some of the health benefits gained in the 2030 baseline scenario.

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