Methane madness

by Stephen Shafer on August 10, 2019

 

Rising unacknowledged  emissions of methane from the natural gas supply chain  are dangerously under-estimated as  a driver  of global heating and must be ended.

Stephen Q. Shafer  MD MA MPH

 

fracking3

                               Aerial view of fracking pad in Pennsylvania  photo source Smithsonian magazine

Summary:  The  natural gas industry  is now  the largest source  of human-influenced methane releases to the air, in the form of “fugitive emissions”  leaked  from the industry’s supply chain.  Though recent measurements are lacking, annual emissions are surely  rising  worldwide as natural gas production booms  via  ” fracking.”    This paper presents a range of  possible impacts from  these fugitive emissions on the atmosphere’s quickening  ability  to trap heat radiated from earth over the next two decades.  The range uses  estimates of leakage proportions from the literature, to which a GWP20 is applied instead of the customary,  illusory GWP100.   

If  methane emissions keep going up  2019-2023,  this short-lived super-potent greenhouse gas will wreck all  hopes of keeping global  temperature rise under + 1.5 C   as of 2030.   Getting  total annual methane  emissions to stop rising  will improve chances.  Natural gas production cannot be allowed to increase year-on-year.    A worldwide ban on fracking is the best response.

           It’s no secret now to dedicated climate activists and fracktivists that the potent  greenhouse gas (GHG)  methane leaks into the atmosphere from the  natural gas supply chain.  Even those  who’ve  heard about these  fugitive emissions, however, usually  know them as a proportion of total  natural gas production, e.g. “2%”  or “7%.”   It’s better to see them as  a quantity  that can be compared on a mass  and temporo-spatial distribution basis  to other streams of atmosphere-heating GHGs such as methane from livestock or  CO2 emitted  in  air travel.  This short paper provides a GHG analysis of  natural gas  through an assessment that is not full life cycle,  but does factor in supply chain losses, not just combustion. 

            To make this  briefing  useful to non-scientists,  scientific terms and abbreviations are minimized.  An unavoidable few are listed below.  It supposes basic knowledge, e.g. that combusting fossil fuels releases carbon dioxide, or that natural gas is mostly methane.    It skips over the physics of  how greenhouse gases heat the atmosphere, which are discussed  in a longer paper elsewhere called “Insurmountable Opportunities” and a  shorter one titled  “Why We Must Control Methane Emissions Now.”

———————————————————————————————————————————————————–

cf          cubic foot   

CH4    methane

cm        cubic meter in this context cubic meter, not centimeter 

CO2      carbon dioxide

CO2-e          CO2 equivalent, which   measures  the efficiency of a specified mass of a GHG at trapping heat in the atmosphere     relative to that of an equal mass of CO2 released  at the same time.  CO2-e has units of mass, e.g. metric tons.  To find CO2-e multiply the  mass of  a  GHG emission  by that gas’s  global warming potential  (GWP).

fugitive  refers to gaseous emissions to air that are neither intended   nor  readily detectable or measurable

GHG     greenhouse gas

Gt          gigaton = billion metric tons = 1 petagram (Pg)

GWP      global warming potential expresses the average efficiency of  a  GHG  at trapping  heat in the atmosphere over a specified time span relative to  that  of  CO2  at the same time.  GWP  has  no mass units, but as noted, does have a time dimension,  often called the “horizon.”  A 100 year horizon is most common. For short-lived atmospheric pollutants like methane a shorter horizon such as 10 or 20 years   is warranted,  though  not adopted  by the Intergovernmental Panel on Climate Change.

mt          metric ton

mmt     million metric tons = 1 Tg = 1 teragram = 1 megaton    Tg used for methane and mmt  for CO2 and CO2-e

NG       natural gas  

tcf         trillion cubic feet

Tg         teragram = 1 mmt

———————————————————————————————————————————————————-

Part 1.  Why “natural gas” may not be better for the atmosphere than coal.    This discussion starts by comparing  the GHG emissions in metric tons  CO2  due to combusting a quantity of   natural gas (which is ~ 95%  methane)  to the emissions  as CO2-e associated with  losses of methane from moving that same quantity thought the natural  gas supply chain  from in-ground  to end -user before combustion.

            Combustion  of  41,900 metric tons of NG  (~ = 2.16 trillion btu ~= 2.12 bcf  ~ = 60 million cm  )  releases 115,000 metric tons of CO2 [ @ 0.053 metric tons CO2 per million btu].    

Important aside on measurement units:  The quantity 41,900 mt  used here  has no special significance .  It has roughly the same  heat energy value that is contained  in  100,000 cubic meters of liquefied natural gas carried by a large LNG tanker.  Natural gas is not usually measured by mass.  It  is not seen as a greenhouse gas   but as a commercial material  of  very low density that is theoretically 100% contained until combustion.  Thus,  production of it  is counted  in volume (e.g.  cubic feet)   or heat value (e.g.  btu or tonnes of oil equivalent),  not in mass.   GHGs like methane, emphatically not contained,   are measured by mass.  This paper is unconventional, but not wrong, to  measure NG by mass.  As cubic feet in the pipe,  natural gas  is “clean, ” a “bridge fuel.”  As metric tons outside  the pipes it  is methane, the bane of vegans and fracktivists alike,   a GHG  86 to 104 times more efficient at trapping heat  in its ten years of life in the atmosphere than is CO2.

            A fairly conservative estimate for the proportion of natural gas  lost as unacknowledged, or fugitive,  emissions  of methane is 2.3%.  Raimi and  Aldana https://www.resourcesmag.org/common-resources/understanding-a-new-study-on-oil-and-gas-methane-emissions/  tabulated  29 reports, all after 2011.  The point estimate in nine of these  was 4% or higher, in four, it was   >2% and <4%.  In the other sixteen, less than 2%.

            Applying  five  hypothetical  supply-chain loss proportions (2%, 2.5%, 3%, 3.2%  and 4%) to the 41,900 metric tons (~= 2.16 trillion btu) of NG  in the example gives supply-chain methane losses in metric tons as 840, 1040, 1260, 1341 and 1670,  respectively.  All five proportions  are  in the lower 55% of the range given by Raimi and Aldana, 

            The  Global Warming Potential  (GWP20)  of methane for a 20 year time horizon is 86,  higher than the GWP100,  cited in most recent places as 25  to  34.   The strong  case for GWP20  for methane is presented elsewhere.   Applying GWP20 to a  loss proportion of  3.2%,  then, fugitive emissions of methane  related to marketing  41,900 mt of NG amount to  115,000 mt CO2–e, equal to  the release from combustion alone

 total emiss graph

Graph 1.  GHG emissions in thousand metric tons CO2-e  for life cycle of 2.16 trillion btu  (~=41,900 mt )natural gas, from below-ground  through  combustion,  by  proportion of natural gas  lost as methane in supply chain and type of gas emitted,  CO2 vs. CH4     GWP20 of 86 used for methane. Total emissions = sum of the blue and red bars. For 3.2% losses, that is 230,000 mt CO2-e.

            Graph 1 displays CO2-e emission from  the life cycle of 2.16 trillion btu  (~41,900 metric tons) of  natural gas.   The size relationships between combustion emissions of CO2 and CO2 equivalents of fugitive emissions of methane will be the same for each loss proportion regardless of the quantity of NG.  With a  supply-chain loss proportion of  just  3.2%,  for example,  fugitive emissions of methane from natural gas are 1341 mt.   By  GWP20, this converts  to  115,000 mt CO2-e,  equal to  the mass of CO2 released from combustion of 41,900 mt NG.  Thus, marketing and burning any quantity  of natural gas doubles the mass of CO2-e when the loss proportion is as low as   3.2%.

            Note well.  Technically, the figure for mass of natural  gas  combusted  might  be lowered by deducting the supply-chain loss not combusted; otherwise,  the  amount lost  is  double-counted, both as methane and as CO2.    Not  making  the adjustment biases the comparison slightly  against the point I make,   that emissions from methane  lost  in the supply chain above a certain  low proportion  double or more than double  total emissions of  GHG from use of natural gas.  The imprecision, even with losses as high as 10%,  is acceptable.

            Parties promoting the expansion of natural gas use declare  it’s cleaner than coal.  The assertion is based only on CO2 released from combustion.   Combusting 2.16  trillion  btu of  bituminous coal at 206 lb CO2 / million btu does  emit 202,000  mt CO2,  much more than the 115,000 mt CO2 from combusting 2.16  trillion  btu  of NG.   Nonetheless, with  a supply-chain methane loss proportion of only 2.5 % added to the combustion emissions, natural gas (115,000 mt CO2 from combustion plus 89,000 mt CO2-e from fugitive emissions = 204 mt CO2-e)  looks worse than coal.   That comparison, however,  is also biased.

            The 202,000  mt CO2-e figure for coal does not account for other GHG releases in the life cycle of coal from extraction to end-use,  such as  mining operations, washing, transportation and methane releases from underground mining.  Nor does it incorporate black carbon,  a short-lived aerosol enormously more efficient than CO2 at trapping heat in the atmosphere.    I can’t do the math on black carbon, can only say that comparing bituminous coal to NG on a life cycle basis might show that   natural gas even with  (say) 4%  supply-chain loss would  look better for atmospheric heating  than coal,  btu for  btu.  I don’t have the needed figures.

           Yet the question of which is “better” is irrelevant.  Humankind cannot afford  to  not  rapidly zero out  CO2 emissions and  to  not start cutting methane emissions from all sources beginning 2019.  The best way to reduce  methane emissions from all human-influenced sources is to go after the biggest single stream: methane losses from  the natural gas supply chain.

This will not be done by promising  to  reduce the loss proportion by upgrading pipes and tightening compressor stations.  It  must be done by ending the growth of  natural gas production before 2021,  then starting  a steady trend downward in production. It is not proposed, not necessary,   to end the use of natural gas  in this  short  time, only to turn the corner from going up to flattening then starting down.

Part 2  Global and domestic trends in natural gas marketing,  and  how they relate to trends in methane emissions        

            Figures for annual emissions of methane worldwide are probably not very accurate.  There  is much disagreement among different sources. A respected source is the multinational Emissions Database for Global Atmospheric Research (EDGAR).  I could not  find  EDGAR  figures beyond  2012 in the public domain.  For a perspective on world emissions to that time, Graph 2 below  shows stable, even slightly lessening emissions from 1990 through 2002 then a 16% rise over the next decade.

 graph2

  Graph 2.  Annual human-influenced methane emissions worldwide by year 1990-2012 in Tg (million metric tons)  Data source EDGAR  graph by Shafer  On the x axis,  92 is 1992,  102 is 2002 and so forth.

            Worldwide  production of  natural  gas  has increased much more than have methane emissions recorded by EDGAR. over the same epoch,   by about 70%  1990-2012, as seen in Figure 1 below. 

 worldNG since1990

Figure 1.   World production natural gas 1990-2018 by region and year in billion cubic meters https://yearbook.enerdata.net/natural-gas/world-natural-gas-production-statistics.html

            Figure  2  below,  from the Global Gas Report     graphs later years 2010-2016   in the above series.  It shows that all the considerable step-up  in NG  “production” since 2010 (and undoubtedly for  a couple of years before that )  is “unconventional.”  

 natgasprod world

Figure 1. World natural gas/fossil gas  production by year 2010-2016 and by method of production in billion cubic meters.  Link to source

            Extending the series in Figure 1 with   a 2017 (3768 bcm)  datum from another source, world  production of  NG  rose by 507 bcm/yr between 2010 and 2017, an average of  +  72 bcm/yr .   That is an increase of about 48.1 million metric tons (Tg)  NG   per year during the current boom in   “unconventional”   production,  better known as  fracking.   If we apply to the annual world production figures through 2017 three loss proportions within the range of estimates given above  by Raimi and Aldana ,  a steady rise in fugitive methane emissions from the natural gas supply chain is predicted..  Graph 3 below presents this.

 Tg methane emitted

 Graph 3.  Imputed methane losses in Tg  from natural gas supply chain worldwide by estimate of  %  total production presumed  lost in supply chain and  year    Data source for NG  production: p. 14 of https://www.igu.org/sites/default/files/nodenews_itemfip.ofeld_file/2018_Global_Gas_Report.pdf

            Before speculating further about how much  methane escapes annually from supply-chain losses, a salient question regarding the worldwide trends above  must be addressed.  “If methane losses from the natural gas supply system are an appreciable fraction  of  production,  why have methane emissions risen  by only about 20% in the same epoch during  which natural  gas production went up 70% ? “ A related,  harder,  question applies to  the  USA.   “Why are recorded annual methane emissions flat or falling in this country (Graph 4 below)  while  natural  gas production has climbed rapidly in the same epoch (Graph 5)?”

            There is not a solid answer to  either question,  yet the divergence between natural gas production growth and  official CH4 emission figures does not  lessen the significance of supply-chain losses as a major source of methane.   The emission figures for USA and  the  world are very likely under-estimated.   We know that atmospheric methane levels are rising apace since about 2006 (see Appendix),  and no one denies  that at least some methane is lost from the supply chain.  It is  a safe assumption that if natural gas production is trending up steeply over time, then methane emissions from that stream are as well. 

 Ch4 by yr USA

 Graph 4  Methane emissions Tg/yr USA by year 2002-2017.  Emissions in CO2-e from  source https://cfpub.epa.gov/ghgdata/inventoryexplorer/#allsectors/allgas/gas/all were divided by GWP100 figure of 25 to convert to Tg  methane.

 

 natgas usa by yr

Graph 5.  Natural gas marketed production  by year 2006-2018 USA in trillion cubic feet  data source  https://www.eia.gov/dnav/ng/hist/n9050us2a.htm      

Part 3.  Projecting the amount of methane fugitive emissions and their contribution to atmospheric heating-up        

            Returning to graph 3  above,   the 4% figure for 2017 is 99.2 Tg/yr.  4%  is slightly above the median value for loss % among the twenty-nine  reports tabulated by Raimi and Aldana  mentioned above.  99 Tg/yr is less than the 157 Tg/yr   for a recent year attributed to the oil and gas sector  by Howarth in a 2019 lecture,  but  close to  the 96 Tg ascribed by Saunois et al to “fossil fuels” for 2012.  99.2 Tg  CH4 adjusted by GWP20 means 8.5 billion metric tons CO2-e  of  methane worldwide for one calendar year from NG alone.   Whatever one sets as an acceptable carbon budget  for  up  to  whatever future year one chooses, 8.5 billion metric tons  CO2-e  in  one calendar year from just one of several sources of the second-most important GHG  is intolerable.

            Non-CO2  GHGs  (methane, nitrous oxide and F-gases) and aerosols are not counted in most carbon budgets, in which  aggressive mitigation is [prayerfully] assumed.  If they were, the budgets for molecular CO2 itself  would have to be smaller than those proffered,   and very much smaller when   GWP20 of 86   is used for methane,  (as it should be  for any epoch  less than twenty years).        

            Some idea of the role  of  methane in a hypothetical all-GHG accounting (as opposed to  one for  CO2 only)  can come from  USA data; comparable figures  for the world are hard to find.  From a recent  EPA inventory through 2017,  Tg of methane  emitted from all human-influenced sources for each chosen year were calculated by  dividing the  CO2-e  listed in mmt  by 25, the  GWP100  for methane often used by EPA.   Multiplying that imputed  CH4  annual release in Tg (mmt)  by GWP20  of 86 returned a much higher value for methane emissions in CO2-e  than is shown  in the EPA table.    The results appear in graph 6 .   For each of the four years included 2002-2017,  there are two columns.  The  CO2-e ascribed to  each gas in the original EPA table is shown in column a,  while column b shows the CO2-e when methane has a GWP20 of 86.  On the average, the grand total in column b is about 24% higher than that in column a and the share of total  due to methane almost three times higher.

 graph6

 Graph 6.  GHG emissions USA in four separate years in million metric tons CO2-e, by gas (CO2 vs CH4 vs  “all other”  (N2O + F-gases)).  For each year the a column uses GWP100 for methane and the b column GWP20

            Graph 6  is most disturbing.   It shows that when methane is given a GWP20,   total US GHG emissions as CO2-e have been, are being or will be  under-counted by about 24% , approximately 1.6  Gt  CO2-e (1.6 billion metric tons CO2-e).  1.6 Gt CO2-e  is  more  than the emissions (1.4 Gt CO2-e)  of the entire industrial sector of the USA  in 2015. Fugitive emissions from fossil fuels  (largely natural gas) make up, conservatively, 40% of that 1.6 Gt CO2-e or 640  mmt  CO2-e .  This is  more than the 582 mmt CO2-e attributed (using GWP100  of 25 )  to agriculture for all GHGs in 2017.

            No matter what GWP is used ,  the fact remains  that,  because of methane’s  short lifetime in the atmosphere,   emissions rising at any rate add to atmospheric heating-up.  Level annual emissions contribute to atmospheric heating without adding to it, while falling total emissions cause relative cooling.  If humankind wants a fighting chance of keeping global average surface temperature less than 1.5 degrees centigrade higher in 2030  than it was in the pre-industrial baseline, natural gas withdrawals must stop rising year-on-year  in 2020.   This turnaround is  the only  avenue for significant course correction on  GHG management over  the next ten years that can have a discernible effect in that time. 

          As Figure 1 showed, all the annual increment in natural gas production  worldwide in the last decade  is due to “unconventional methods” i.e. fracking.  A worldwide ban on fracking  must be enacted in 2019.  The US should lead.

              Thanks to Ken Dolsky for  his  meticulous help with  line-editing   All remaining  errors of orthography or clarity or fact are  on my head.

             Permission is hereby granted  to  reproduce this blog  elsewhere in whole or in part as long as the permalink is cited . http://www.anchorageromneys.com/2019/08/methane-madness/

 

Appendix  on trends in atmospheric methane levels

Global atmospheric methane levels have risen enormously in the last 150 years.  Click on the link to see a graph  too faint to reproduce here.   Since about 2006  there has been a decided upsurge after a brief plateau

global ch4 levels

For speculative commentary from Climate Nexus click here.

 

 

Over-heaters Anonymous:the Methane Diet

by Stephen Shafer on June 24, 2019

                        flooded streets                    

                                                       Why We Must Control  Methane Emissions Now!

Note:  the title of this post has been changed to that immediately  above,  because the original title was a weak pun about a serious topic.  I have not changed the permalink,, since that is in  circulation already.  http://www.anchorageromneys.com/2019/06/over-heaters-a…e-methane-diet

Summary:  This picture-essay   explains  why methane  must be considered very differently from  carbon dioxide as a “greenhouse gas” that powers “global warming.”     It  opens with a brief explanation of global warming, then compares how methane and carbon dioxide differently affect  the capacity  of the atmosphere to trap heat over time.  Humanity has a chance to modify over the next ten years  how methane will influence  near-future global  warming.  To change it for the better is possible.   We don’t have that potential with carbon dioxide.  Therefore, we must act on methane immediately.    The best place to start  is by ending the growth of the natural gas supply system in the United States. 

            A windows-up car in winter sun is very warm inside.  The sunlight  that went  through the glass has been  repacked  inside to  another form of  energy (infra-red) that can’t get out  through glass as readily  as  the light came in; so, some   stays a while, warming the  inside.   Greenhouses work  this way,  too,  trapping heat. 

            Earth’s  atmosphere acts like  glass  because “greenhouse gases”  in it let through solar energy but  restrict the return to space of  infra-red, heating  the atmosphere.    For thousands of years the atmosphere acted   like a well-run greenhouse, with carbon dioxide ( the main greenhouse gas)  recycled  to earth so it did not build up in the atmosphere.  In the 1800s,  mounting  releases  of greenhouse gases   (mostly carbon dioxide from burning fossil fuels for heat and power)  overloaded the atmosphere’s pre-industrial ability to handle them.   Each year, less incoming energy escaped back into space.  This trend has sped up greatly in the last fifty years.  The needed,   beneficial “greenhouse effect”  that fostered  plant and animal life is  out of control.  This raises the  average  temperature at Earth’s surface.  It   causes “climate change”  featuring  rising sea levels,  warmer and acidifying oceans, deadly heat waves, droughts , mass extinctions, melting glaciers,    record-breaking rains and floods.

            Carbon dioxide from burning coal, oil and natural gas accounts for more than half  of  the  heat now stuck  in the atmosphere.  Any carbon dioxide  beyond what  can be recycled to earth via photosynthesis in plants  or (with ill effects) dissolved  in oceans builds up  in the atmosphere, where it  will last  for  centuries.  Another greenhouse gas, methane,  is scarcer but so much  stronger  per molecule at stopping  outward-bound energy that methane causes almost  a third as much heat-trapping as carbon dioxide.     Methane is short-lived.  It survives  in the atmosphere only about ten years before it’s  broken up   by “scrubber” chemicals.  This gives  humans potential to get  more control on   global over-heating  than we now have,  if and only if we take steps that are big but not impossible.. 

            How methane and carbon dioxide differ as atmospheric heat-trappers is  shown in a series of  eight pictures below.  The first four  represent the atmospheric warming effect of  just methane alone; the next four,  the atmospheric warming effect of  just carbon dioxide alone.  In real life the two gases are combined  in the atmosphere, with their combined warming effect being that of carbon dioxide PLUS that of methane.

            The atmospheric warming effect of  methane alone  in 2019  is represented in figure 1 by two  blankets on the doll. Imagine she’s a real person who’s comfortable under two. 

 two blankets

Fig. 1  Warming effect of methane in 2019.  Two blankets

          If global methane emissions stayed the same per year for the next ten years,   each unit entering  the atmosphere after 2029  would replace one that had been scrubbed out.  This would sustain global heating by methane  at  2019  levels but not make it worse.  The 2029 situation is represented in figure 2 .   The doll still has two blankets.

 

two blankets Fig 2. Warming effect of methane in 2029 if  amount emitted each year since 2019 has not changed

        If  global methane emissions began to go down year by year, there would be cooling in 2029,   because not all the  heat-trapping methane molecules that had been scrubbed out would be replaced by new ones.  The doll in figure 3 is “sleeping cooler”   with now only one  blanket, not  two.

 one blanket

 Fig. 3.  Warming effect of methane 2029 after 10 yrs of emissions going down every year ,  not to zero

            On the other hand –worst case – if methane emissions keep rising worldwide,  methane  will add  to global over-heating at an extreme rate.  You can imagine that  the  doll in Figure 4 below will be very hot  under four blankets.

 4 blankets

 Figure 4 .  Warming effect of  methane in 2029 after ten years of rising emissions.

            Someone  might say “Duh, obviously when emissions are going up the  heating effect is stronger, like more blankets.  Everybody knows that.”  OK,  but what  everybody does  not  know is that  the heat content of the atmosphere will respond quickly to changes in how fast  methane is entering  it,   because methane is short-lived.   It doesn’t work that way with  long-lived carbon dioxide.   The response is delayed, blunted.  With  either  gas, emissions going up year after year  will increase atmospheric heat content (add blankets) and raise the doll’s temperature.  BUT, carbon dioxide’s contribution to  atmospheric heat content,  unlike methane’s, will keep rising for decades  even if emissions are flat, even if they  are falling. 

            Figure 5 represents the warming effect of carbon dioxide in 2019: six blankets

 6 blankets

  Figure 5.  Warming effect of carbon dioxide alone  in 2019 represented by 6 blankets

 

         Figure 6 shows the situation in 2029 assuming that carbon dioxide emissions have been exactly the same amount per year since 2019.  Eight blankets, not six. All the heat-trapping gas emitted in those ten years has been added to what was already there in 2019.

8 blankets

  Fig, 6  Warming effect of carbon dioxide alone in  2029 if emissions each year   are unchanged: 8 blankets

           

            If carbon dioxide emissions got to be  less each year than the year before, the situation in 2029 would look like figure 7.   There are seven  blankets, not six  and not eight.  The total added in ten years is less than what it would have been if the amount each year had stayed the same, but it’s still a big extra load.

 seven blankets

   Figure 7. Warming effect of carbon dioxide in 2029 after 10 years of falling emissions

            If  each year’s emissions of carbon dioxide were higher than those the year before,  the scene in 2029 would be like Figure 8, with nine blankets piled on,

 9 blankets

   Fig. 8  Warming effect of carbon dioxide in 2029 after 10 years of rising emissions: 9 blankets

            The table below  summarizes the eight pictures by counting the number of blankets in each situation. For example, two blankets for methane in 2019 (Figure 1) and seven for carbon dioxide in 2029 after ten years of declining emissions.(Figure 7).    The take-home message is that the future heat trapped (number of blankets) due to carbon dioxide will always be higher than that of today for many decades to come,  no matter whether the amounts released per year stay the same, go up or go down.  Methane is different.  Future heat-trapping  due to methane will not necessarily be higher; it could be the same or even lower if humankind takes ambitious steps. 

 

Methane

Fig no.

Carbon dioxide

Fig no.

2019 “baseline”

2

1

6

5

 2029 emissions same each year

2

2

8

6

2029 emissions falling each year

1

3

7

7

2029 emissions rising each year

4

4

9

8

 

            To put things another way,  humanity can apply the brakes to methane’s role in adding heat to  the atmosphere.  There are no brakes on carbon dioxide that will work anywhere near as soon.

            Even cutting   global methane emissions to zero  (impossible, since  almost half are  from sources outside human influence like wetlands and  lakes) would not halt  the runaway  greenhouse effect we see now.  To turn the corner on over-heating, carbon dioxide emissions must end and  much of  it  now in the atmosphere  must  be moved into soil for good.  The point about methane, however, is that  letting  its yearly emissions grow will add hugely  to global over-heating .  but  holding them steady will not.   Cutting them year after year will actually remove heat. 

            To be clear: neither holding total methane emissions steady over the next few years  nor sharply reducing them will necessarily keep the average temperature on the globe’s surface from hitting  dangerous new heights towards  which it is headed.  The other side of that statement is that letting methane emissions continue to go up in the near future guarantees that the danger point will be reached, and sooner.

            How to get yearly methane emissions down ?  The major sources under human influence are, in order of amount : fossil fuel extraction and distribution; livestock  that release methane in digestion; paddy rice cultivation,  landfills and waste handling; biomass burning.

 pie Howarth jpg

  Figure 9. Global human-influenced methane emissions in million tonnes/yr, by source.  Data:  Howarth, 2019

            The major  source – fossil fuels — is also the only one that on good evidence is getting bigger each year.  This is due  largely  to  leakage of methane from the natural gas withdrawal   and distribution system (natural gas is mostly methane) .   In the USA, natural gas withdrawal rose by 69% between 2006 and 2018, spurred by “fracking.”  The more natural gas is pumped from the earth,  the  more methane leaks   into the atmosphere.  A quick end to  growth  of the natural gas industry  in the  USA could put the world on course to steadily  flat or falling methane emissions, not adding further  to atmospheric heat , maybe even lessening it over time .  Continued expansion of  leaky natural gas systems, in terrible contrast, would cause yet more  heat to be trapped our atmosphere,  already too warm.

            A “quick end” to growth does not mean that everyone who now uses natural gas will have it turned off.   It  does  mean that no new projects to withdraw and use it can be tolerated if we want a decent  chance for a livable world for our children and grandchildren.  In short,

  • No new gas wells, fracked or conventional
  • No new gas pipelines, long or short
  • No new gas-fired power plants
  • No new gas storage facilities
  • No new buildings hooked up to natural gas
  • No exports of liquefied natural gas for  fuel or plastics
  • Start closing  “fracked”  wells
  • Carbon fee (and dividend)  on natural gas (with agricultural exemption)
  • Top priority for renewable energy sources like wind and solar
  • No federal subsidies for natural gas systems

            That’s a tall order, but to get from current rate of growth/yr  in methane emissions to no growth could almost be done by rolling  US natural gas withdrawals back  to where they were around 2006 and  making sure that methane from livestock holds steady. 

 

Further reading

http://www.eeb.cornell.edu/howarth/documents/Howarth_methane-Biogeo-lecture_2019-0301.pdf

https://foodsource.org.uk/building-blocks/agricultural-methane-and-its-role-greenhouse-gas

Stephen Q. Shafer MD MA MPH  Saugerties NY 12477   sqs1@columbia.edu

 Any errors of fact or interpretation are entirely mine as an individual. as are all opinions expressed.  Permission is hereby given to copy or circulate  the above piece in whole or part as long as the permalink is cited.

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