Methane and CO 2 emissions from the natural gas supply chain: an evidence assessment

Transcription

1 Methane and CO 2 emissions from the natural gas supply chain: an evidence assessment October 2015 Paul Balcombe Sustainable Gas Institute p.balcombe@imperial.ac.uk #SGI_London Download at: sustainablegasinstitute.org/white-paper-1

2 CONTENTS Background o Greenhouse gas emissions o The supply chain o Previous studies Aims and Scope Methodology Results summary Key findings

3 GREENHOUSE GAS EMISSIONS Natural gas combustion produces half the carbon dioxide emissions compared to coal But this is not the full story 1. Supply chain emissions 2. Methane Strong greenhouse gas Combustion emissions (g CO 2 / MJ) Source: EIA 2015

4 THE SUPPLY CHAIN Methane emissions Vents Leaks Carbon dioxide emissions Fuel combustion Flaring

5 PREVIOUS STUDIES Motivation: US shale gas production increase In 2011, 1 st estimate of greenhouse gas of shale: Natural gas may be worse than coal Prompted greater investigation Different conclusions and estimation methods We need clarity Plus many more

6 AIMS Conduct a comprehensive and transparent review of studies on methane and CO 2 emissions across the whole natural gas supply chain 1. What is the range of estimated CO 2 and methane emissions? 2. What are the reasons for the different estimates? a) Different estimation methods b) Lack of data, or difference in assumptions made c) Different natural gas extraction points, processes, transport and storage steps etc. Provides an evidence base for industry to help address the issues

7 SCOPE Including: All stages from pre-production to delivery to the consumer Onshore/ Offshore Conventional Shale Tight sands Coal bed methane Liquefied Natural Gas (LNG) Excluding: Associated gas End-use combustion sustainablegasinstitute.org/white-paper-1

8 METHODOLOGY

9 OUR EXPERT PANEL David Allen, University of Texas Jim Watson UKERC Lisa Walker BG Group Laurence Stamford Manchester University Djamila Amimer Shell Adam Brandt Stanford University

10 METHODOLOGY

11 RESULTS 424 papers collected Over 250 selected for analysis Government NGO Academic Industry Engineering calculations Life cycle assessments Reviews US Primary measurement Europe Global Asia

12 KEY FINDINGS 1. The reported range of greenhouse gas emissions is vast 2. Evidence of super emitters all across the supply chain 3. Key emission sources 4. Revised estimate of emissions for supply chains using modern equipment and effective operation and maintenance procedures 5. Significant methodological differences 6. Lack of data 7. Further research needs sustainablegasinstitute.org/white-paper-1

13 1. OVERALL GHG EMISSIONS Greenhouse gas emissions: g CO 2 eq./ MJ Greenhouse gas emissions (g CO 2 eq./ MJ HHV) g CO 2 eq. Carbon dioxide plus methane (methane = 34 x CO 2 ) / MJ Energy content of the gas delivered to consumer White paper: Section 3.1, page 19

14 1. OVERALL GHG EMISSIONS Coal combustion emissions Greenhouse gas emissions (g CO 2 eq./ MJ HHV) Gas combustion emissions 1. The range of reported estimates is vast White paper: Section 3.1, page 19

15 OVERALL GHG EMISSIONS Greenhouse gas emissions (g CO 2 eq./ MJ HHV) White paper: Section 3.1, page 19

16 1. OVERALL GHG EMISSIONS Greenhouse gas emissions (g CO 2 eq./ MJ HHV) 1. The range of reported estimates is vast 2. Some secondary data less robust 3. Potential super emitters White paper: Section 3.1, page 19

17 2. OVERALL METHANE EMISSIONS White paper: Section 3.1, page 20

18 3. KEY EMISSION SOURCES

19 4. REVISED EMISSIONS ESTIMATE Raw literature Remove primary measurements for non-modern equipment/ practices Remove less robust/ transparent/ over-conservative secondary estimates Best available technique (B.A.T.) estimate, using modern equipment and effective operation and maintenance procedures.

20 4. REVISED EMISSIONS ESTIMATE Ranges are reduced significantly White paper: Section 4.1, page 38

21 4. REVISED EMISSIONS ESTIMATE Methane only (% vol/vol of extracted methane) Research need: identify further reductions, how much can emissions be reduced to? White paper: Section 4.1, page 41

22 4. REVISED EMISSIONS ESTIMATE Methane dominates emissions During extraction and transmission, storage and distribution stages T,S&D emissions will be highly variable White paper: Section 4.1, page 42

23 5. METHODOLOGICAL DIFFERENCES Variety of methods used to estimate and measure methane emissions For example, use of different global warming potential values: White paper: Section 4.4, page 57

24 6. DATA We have entered a new phase of primary data collection This must continue: Across regions Well types More challenging stages, e.g. T,S&D Offshore

25 CONCLUSIONS Comprehensive review of supply chain GHG emissions Extremely large range in supply chain GHG emissions. Overall estimates: 2-42 g CO 2 eq./ MJ HHV Key emission sources from the literature are Well completions (unconventional) Liquids unloading Pneumatics Compressors The presence of a few super emitters skew average emissions significantly There remains a lack of representative data with respect to Different regions other than the US Some key emission sources, in particular liquids unloading

26 THANK YOU Paul Balcombe #SGI_London Download the full paper at: sustainablegasinstitute.org/white-paper-1