The CO₂ associated with natural gas supply reported by local distribution companies (LDCs) varies due to fluctuations in weather, the relative price of natural gas compared to other fuels and the prevailing economic conditions. The annual CO₂ reported for natural gas supplied by LDCs has ranged between a low of 709.5 .   For suppliers of natural gas liquids (NGLs), the reported CO₂ associated with NGLs supplied to the U.S. economy (i.e., ethane, propane, butane, isobutane and pentanes plus) has gradually increased from 211.4 million metric tons (MMT) in 2012 and a high of 826.2 MMT in 2022 and is directly proportional to the quantity of natural gas supplied. The total volume of natural gas supplied increased by 10.2% in 2018 and by 0.6% in 2019. In 2020, natural gas supplied decreased by 5.8% percent, but rebounded slightly in 2021. However, the CO₂ reported in 2021 was 31.6 MMT lower than the 2019 high of 822.5 MMT. The increase in natural gas supplied in 2018 and 2019 was primarily due to economic growth, relatively low natural gas prices resulting from high levels of natural gas production, and greater reliance on natural gas to fuel power plants. [1, 2, 3] The lower annual CO₂ emissions reported for 2020 is due to a reduction in demand by residential, commercial (which includes restaurants, hotels, and schools), and industrial consumers. Natural gas supplied to residential, commercial, and industrial customers in 2020 decreased by 6.7 percent, 10.1 percent and 5.9 percent, respectively, compared with 2019, despite the lower natural gas prices. [3] The decrease in natural gas consumption by residential users is likely due to milder winter weather in January - March 2020 and November – December 2020, while the lower consumption in the commercial and industrial sectors is likely caused by plant closures caused by the COVID-19 pandemic. [4] Natural gas consumption by the electric power sector increased by 4 percent in 2020. In 2022, natural gas consumption increased across all sectors, with the largest increases occurring in the commercial and residential sectors, where consumption increased by 6.7% and 5.2% respectively. [8]  Increases 2011 to 465.0 MMT in 2022. Except for a small decrease in 2013, the supply of NGLs has increased steadily every year with ethane and propane making up 70.9% by volume of the NGLs supplied each year by U.S. fractionators. [1]

The increase in reported NGL supply is due to increased production of natural gas in areas that are high in natural gas liquids, increased U.S. demand for NGL products, and increased exports. [2, 3, 4] Production capacity, however, decreased due to fewer fractionation plants reporting to GHGRP (114 plants in 2022 compared with 116 in 2011). The ratio of CO₂ to number of plants reporting has, therefore, increased from 1.85 MMT CO₂/plant in 2011 to 4.1 MMT CO₂ /plant in 2022. Although the number of plants reporting in 2022 decreased from a high of 124 in 2020 to 114, the CO₂ per plant increased from 3.5 MMT CO₂/plant in 2020 to 4.1 MMT CO₂ /plant in 2022. The year-over-year increases in the CO₂ emissions associated with NGLs were 11.7% for 2018 and 2019, 8.2% for 2020, 5.8% for 2021, and 1.5% for 2022. Domestic consumption of NGLs increased by 49.3% from 2.25 million barrels per day in 2011 to 3.36 million barrels per day in 2022. [4] Increases in ethane supply between 2017 and 2022 are in part a response to the completion of new petrochemical facilities in the U.S. that use ethane as a feedstock. [5] However, the increase in annual NGL production reported in recent years is driven primarily by increases in exports due to high international demand and expansion of U.S. export facilities through the construction of new pipelines and export terminals. [2, 3, 4]. The U.S. currently produces more NGLs than it consumes on an annual basis. Exports of NGL products increased from 0.25 million barrels a day in 2011 to 2.41 million barrels per day in 2022 (864% increase). [4] Although exports of all NGLs have increased over the decade, exports of propane have increased the most and make up the largest share of total NGL exports. Exports of propane increased from 0.30 million barrels per day in 2013 to 1.40 million barrels per day in 2022 driven by strong market demand in Asia. [3, 4] in the residential and electricity sectors in 2022 were 5.2% and 7.9% respectively. [8] The average natural gas price for residential customers increased from $12.18 per thousand cubic feet in 2021 to $14.75 in 2022. [5] Natural gas consumption in the electricity sector has increased each year since 2018 and is due in part to low gas prices and the retirement of coal-fired power plants. Although natural gas consumption by the electricity sector decreased slightly in 2021.[8]. Natural gas consumption by the electricity sector grew by 19.3 million cubic feet in 2021 from the 49.7 million cubic feet consumed in 2020 and may be due to higher natural gas prices in 2021. The average natural gas price paid by power plants in 2021 was double the price in 2020. [2, 3, 5, 6, 7].

The reported CO₂ for 2011 and 2012 are also affected by changes in the default emission factors. The default emission factor for natural gas supplied was revised in 2013 to a value about 1% less than For suppliers of natural gas liquids, the default emission factor used in years prior to 2013. For an LDC that uses the default emission factors, the total CO₂ value reported in 2013 and subsequent years is 1% lower than what would have been reported if the emission factor had not been updated. Since many LDCs use emission factors developed using their own data, the overall impact on CO₂ for the sector is small. However, the total CO₂ for the sector is lower for 2013 and subsequent years factors used for calculating the CO₂ for ethane, propane, butane and isobutene were revised in 2013. The default emission factors for propane, butane and isobutane were increased by a few percentage points over the factors used prior to 2013, while the default emission factor for ethane  decreased by over 30 percent. The impact these changes had on the total CO₂ reported by an NGL fractionator depends on the mixture of products the plant supplies and whether the fractionator used the default value or a measured value. Since most NGL fractionators supply ethane, the reported CO₂ across the industry was lower beginning in 2013 than would have been reported if the emission factor had remained unchangedfactors had not been updated.

[1]          U.S. Department of Energy, Today in Energy Information Administration, U. S. Energy Information Administration/Petroleum Supply Annual 2022, Volume 1, Table 15. Natural Gas Plant Net Production , Consumption, and Exports Set New Records in 2019, October 5, 2020and Stocks of Petroleum Products by PAD and Refining Districts, 2022, January 26, 2024. Available at: https://www.eia.gov/todayinenergy/detail.php?id=45377/petroleum/supply/annual/volume1/pdf/table15.pdf.

[2]          U.S. Department of Energy, Energy Information Administration, Today This Week in EnergyPetroleum, In 2019, the United States Produced and Consumed Record Volumes of Natural Gas, July 102020, Increased Propane, Other HGL Exports Contribute to Continued Strong Product Exports Despite Reductions in Major Transport Fuels, September 23, 2020. Available at: https://www.eia.gov/todayinenergy/detail.php?id=44336petroleum/weekly/archive/2020/200923/includes/analysis_print.php.

[3]     U.S. Department of Energy, Today in Energy , In 2020, U.S. Natural Gas Prices were the Lowest in Decades, January 7Information Administration, The United States Exported More Propane than Distillate in 2020, March 8, 2021. Available at: https://www.eia.gov/todayinenergy/detail.php?id=4637647036

[4]     U.S. Department of Energy, Today in Energy , U.S. Natural Gas Consumption was Lower in 2020 in All Sectors Except Electric Power, March 10, 2021. https://www.eia.gov/todayinenergy/detail.php?id=47076[5]     U.S. Department of Energy, U.S. Energy Information Administration, Monthly and Annual Natural Gas Prices. Available at https://www.eia.gov/dnav/ng/ng_pri_sum_dcu_nus_a.htm.[6]     U.S. Department of Energy, Today in Energy, More than 100 Coal-fired Plants have been Replaced or Converted to Natural Gas Since 2011, August 5, 2020 Hydrocarbon Gas Liquids Explained: Imports and Exports of Hydrocarbon Gas Liquids, December 26, 2023. Available at: https://www.eia.gov/todayinenergy/detail.php?id=44636.

[7]     U.S. Department of Energy, Today in Energy, In the past 20 years, natural gas has displaced most coal-burning generation in Pennsylvania, January 26, 2023. Available at https://www.eia.gov/todayinenergy/detail.php?id=55319

[8] U.S. Department of Energy, U.S. Energy Information Administration, Natural Gas Consumption by End Use. Available at https://www.eia.gov/dnav/ng/ng_cons_sum_dcu_nus_a.htm/energyexplained/hydrocarbon-gas-liquids/imports-and-exports-of-hydrocarbon-gas-liquids.php.

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