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ממדינה שכמעט גמרה את רזרבות הגז ארה"ב הפכה למעצמת גז מחדש ודבר מאפשר שימוש קטן יותר בפחם. אבל הגז מופק באמצעות סידוק הידראולי hydraulic fracturing או הידרופרקינג hydrofracking טכנולוגיה שבה מוזרקים לקידוח מים עם כל מיניי חמרים בתוספת חול בלחץ גבוה. התוצאה היא שמיתן ועוד כל מיני חמרים מגיעים לאן שהם לא רצויים ואז ברז המים במטבח הופך לגירסה מוקטנת של המזרקה של אגם אם מקרבים אליו גפרור בוער. לפי הערכה אחת דליפות המיתן בטכנולוגיה הזאת עלולות לבטל את היתרון שיש לגז טבעי על פחם מבחינת שינויי האקלים.
בארץ הוקרן הסרט התעודי Gas Land
כיום אין שימוש בארץ בטכנולוגיה הזאת אבל אם היזמים של הוכנית להוציא נפט מסלעי השפלה יגיעו למסקנה שכך אפשר יהיה להוציא יותר נפט יותר מהר מהסלעים האטומים יחסית.....
PNAS 2011- Osborn Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing - pdf
A Fresh Scientific Defense of the Merits of Moving from Coal to Shale Gas - NYTimes.com
Climatic Change DOI 10.1007/s10584-011-0061-5
LETTER
Methane and the greenhouse-gas footprint of natural gas from shale formations
Howarth et al .Accepted: 13 March 2011 © The Author(s)
This article is published with open access at Springerlink.com
Abstract We evaluate the greenhouse gas footprint of natural gas obtained by high- volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life- time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.
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Fig. 1 Comparison of greenhouse gas emissions from shale gas with low and high estimates of fugitive methane emissions, conventional natural gas with low and high estimates of fugitive methane emissions, surface-mined coal, deep-mined coal, and diesel oil. a is for a 20-year time horizon, and b is for a 100-year time horizon. Estimates include direct emissions of CO2 during combustion (blue bars), indirect emissions of CO2 necessary to develop and use the energy source (red bars), and fugitive emissions of methane, converted to equivalent value of CO2 as described in the text (pink bars). Emissions are normalized to the quantity of energy released at the time of combustion. The conversion of methane to CO2 equivalents is based on global warming potentials from Shindell et al. (2009) that include both direct and indirect influences of methane on aerosols. Mean values from Shindell et al. (2009) are used here. Shindell et al. (2009) present an uncertainty in these mean values of plus or minus 23%, which is not included in this figure
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