Methane Emissions in the Natural Gas Life Cycle and Implications for Power Generation: Update on Emission Studies

Transcription

1 Methane Emissions in the Natural Gas Life Cycle and Implications for Power Generation: Update on Emission Studies Presentation for the Western Interstate Energy Board March 17, 2015 Tom Curry

2 Key Takeaways Recent bottom-up studies of emissions from natural gas systems have reinforced the idea of a fat-tail issue where a small percentage of sources are responsible for a large percentage of emissions EPA continues to refine the GHG Inventory to reflect reported data and recent studies, while source contributions have changed, total emission estimates have remained fairly steady across recent inventories Recent top-down studies highlight significant regional variability which could contribute to the disparity between bottom-up approaches and earlier top-down studies Natural gas combined cycle power plants have about half the life cycle greenhouse gas emissions of coal-fired power plants 2

3 Estimating Fugitive and Vented Methane Emissions Top-down Studies Measurements of emissions at facility to national scales, typically take at a location remote from individual pieces of equipment Bottom-up Studies Direct measurements of emissions at the device or facility level are used to develop emission factors Inventories based on emission factors and activity data Life cycle assessments based on inventories and measurements Photo Source: EPA Gas STAR ( Photo Source: CIRES/NOAA ( 3

4 NOAA-led Top-down Methane Measurement Studies Bakken Upper Green Valley Uintah Denver- Julesburg Fayetteville Marcellus Haynesville Study Completed Study Planned Eagle Ford Source: EIA, MJB&A Analysis 4

5 Emission Rate (%) Top-down Study Estimated Emission Rates 12 Published Pre-2015 Published Denver-Julesburg (2008) Denver-Julesburg (2012) Uinta (2012) Fayetteville (2013) Haynesville (2013) Marcellus (2013) 5

6 Emission Rate (%) Production Rate (10 7 cubic meters/day) Basin Emission and Production Rates 12 Published Pre-2015 Published Denver-Julesburg Denver-Julesburg (2008) (2012) Uinta (2012) Fayetteville (2013) Haynesville (2013) Marcellus (2013) 0 6

7 Natural Gas System Emission Sources by Segment Methane Emissions Rate: Million metric tons CH EPA GHG Inventory Implied 2012 Methane Emissions Rate (CH 4 /NG Produced): 1.18% % 0.2% 0.4% Production and Gathering Processing Transmission and Storage % Distribution Source: MJB&A analysis, EPA 2014 GHG Inventory, EIA Total U.S. Gross Natural Gas Withdrawals 0.0 7

8 Continued Progress on Bottom-Up Studies Segment Component/Activity Direct Emissions Measurements Scaled to National Emissions Notes Well completions and Allen et al. Phase I workovers Pumps and other Allen et al. Phase I equipment leaks Production & Gathering Pneumatic controllers Allen et al. Phase I & II Liquids Unloading Allen et al. Phase I & II Gathering facilities National estimate comparison in review Processing Processing plants National estimate comparison in review Transmission & Storage Compressors National estimate comparison in review Distribution Distribution networks City mapping data released, direct measurements forthcoming = Study published 8

9 Consistent Themes from Bottom-Up Studies Emission factors used by EPA and others should be updated Some should be adjusted up, others down Despite changes in specific emission factors, overall inventory appears to be consistent with released studies Site-level emission rates are skewed, with a small number of sources contributing a large percentage of overall emissions Findings of superemitters across the studies Evidence of regional variability with sources emitting at different rates in different regions Accuracy of EPA s GHG Reporting Program could be improved by increasing direct measurement 9

10 Recent Production Studies Compared to Inventory Emissions Source UT Austin Studies 2014 GHG Inventory 2015 GHG Inventory (Draft) Flowback from Hydraulically Fractured Wells 2012 Production Emissions Across Inventories (thousand metric tons CH 4 ) Chemical Pumps Pneumatic Devices Liquids Unloading Other Sources 1,218 1, Total EPA Production Emissions Leak Rate (CH 4 / NG produced) 2,185 1,992 2, % 0.35% 0.37% 10

11 Natural Gas System Emission Sources by Segment 2014 EPA GHG Inventory Implied 2012 Methane Emissions Rate (CH 4 /NG Produced): 1.18% 2015 EPA GHG Inventory Implied 2012 Methane Emissions Rate (CH 4 /NG Produced): 1.20% Million metric tons CH Production and Gathering 2015 Draft Processing Transmission and Storage Distribution Source: MJB&A analysis, EPA 2014 GHG Inventory, EIA Total U.S. Gross Natural Gas Withdrawals

12 MJB&A Life Cycle Assessment Estimated Life Cycle Emissions for Natural Gas- and Coalbased Electricity Generation (100-year GWP) lb CO 2 e/ MWh NGCC Coal Upstream fugitive and vented CH Natural Gas, 2015 Inv (NGCC) Fuel (Combustion Technology) Coal (Fleet Average Boiler) Other Upstream GHGs CO 2 from electricity generation Assumed Combustion Efficiency: NGCC: 51% Avg Coal: 34% GWP=34; Natural Gas, 2014 Inv based on 2014 EPA GHG Inventory less distribution segment emissions. 12

13 Life Cycle Emissions at Different Emission Rates 100-year GWP lb CO 2 e/ MWh Estimated Life Cycle Emissions for Natural Gas- and Coal-based Electricity Generation (GWP = 34) Avg Coal Boiler Total Emissions Avg Coal: 2331 lb CO 2 e/mwh Difference between NGCC and Coal NGCC Upstream fugitive and vented CH 4 Other Upstream GHGs CO 2 from electricity generation 0 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16% Vented and Fugitive Methane Rate for Natural Gas (production through transmission) 13

14 Life Cycle Emissions at Different Emission Rates 100-year GWP lb CO 2 e/ MWh Estimated Life Cycle Emissions for Natural Gas- and Coal-based Electricity Generation (GWP = 34) Technology (Efficiency) Avg Coal Boiler (34%) Supercritical Coal Boiler (39%) Avg NGCC (51%) Avg Coal: 2331 lb CO 2 e/mwh (34%) SC Coal: 2019 lb CO 2 e/mwh (39%) NGCC Upstream fugitive and vented CH 4 Other Upstream GHGs % 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16% Vented and Fugitive Methane Rate for Natural Gas (production through transmission) CO 2 from electricity generation 14

15 Life Cycle Emissions at Different Emission Rates 100-year GWP (Comparison of Power Plant Efficiency) lb CO 2 e/ MWh Estimated Life Cycle Emissions for Natural Gas- and Coal-based Electricity Generation (GWP = 34) Technology (Efficiency) Avg Coal Boiler (34%) Supercritical Coal Boiler (39%) Avg NGCC (51%) Avg Coal SC Coal Range for NGCC (45% to 60%) Range for Simple Cycle (30% to 40%) % 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16% Vented and Fugitive Methane Rate for Natural Gas (production through transmission) 15

16 Ongoing Research and Emerging Issues Upcoming bottom-up and top-down studies will provide better understanding of emissions from individual sources and gas production regions Better account for regional emissions variations and activity data Airborne emissions measurements over western U.S. shale gas and tight oil basin Will also measure emissions from surface coalmines, oil pipelines, coal and gas power plants, and biofuel refineries Updating Inventory methodologies Regional data from direct measurements to play larger role in estimating national emissions Revisions to the GHG Reporting Program Apportionment studies assigning methane to natural gas production or petroleum production 16