The Econmist - USA (2021-10-30)

The Economist October 30th 2021 Special report Stabilising the climate 25

erhasbeenaroundfordecades.Theunfcccaskedtheipcctopro­
ducea reportonthetechnology 20 yearsago.Yetthereisstillnota
singlelargegas­orcoal­firedpowerstationthatiscapturingand
storingitsemissions.
Oneproblemisthatfossil­fuelindustriesandgovernments
thatvaluethemhaveaninterestinsayingtheyarepursuingccs,
becauseitseemstoprovidea futureforsomefossilfuels,butno
pressingreasontomakeitanimplementedreality.Thetechnolo­
gymakesplantsmoreexpensiveandlessefficient,andintheab­
senceofa highcarbonpricethatisa penaltynobodywantstopay.
Whatismore,manypeople—sometimestermed“numbies”,for
“notundermybackyard”—disliketheideaofindustrialwastebe­
ingsquirted into aquifers and gasfieldsanywhere near their
homes.HencetheattractionofshippingittoIcelandwhereitcan
beturnedintosolidrock.
Givenallthis,itisa problemthatthetechnologiesonwhich
ccsreliesarenowcentraltoclimateaction,thankstothespreadof
net­zeropledges.It isnotjustthattheserequiredecarbonisingce­
ment­making(forwhichccslookscrucial),orthattheyhavea role
forhydrogen(which,ifmadefromfossilfuels,needsccstobe
clean).ItisthatatsomepointtheyneedCO 2 tobedrawndown
fromthethinbutthickeningairandstoredaway.

Takebackwhathurtyou
Next to Carbfix’s operation at Hellisheiði is Orca, a facility built in
partnership with Climeworks, a Swiss company. Fed with air from
a bank of 96 industrial fans, Climeworks’s technology filters out
atmospheric CO 2 so it can be fed into the geothermal plant’s waste­
water for disposal at depth. Orca, which opened in September, is
the world’s largest “direct­air capture” (dac) facility. Its 11 tonnes of
carbon  captured  each  day  are  the  forerunner  of  an  enterprise
which, if models are right and pledges are adhered to, will grow a

millionfold in the next half­century. 

The  negative  emissions  dac is  held  to

offer  play  two  roles  in  climate  stabilisa­

tion.  One  might  be  seen  as  balancing  the

current  carbon  account.  Although  most

emissions  can  theoretically  be  eliminated

using  technologies  that  exist  now,  avia­

tion,  shipping  and  some  industrial  pro­

cesses  remain  hard  to  decarbonise.  Some

agricultural  greenhouse­gas  emissions

look  as  if  they  will  prove  recalcitrant.  As

long as emissions of long­lived greenhouse

gases  persist,  stabilisation  will  require

negative emissions.

The  other  role  for  dacis  getting  rid  of

historical  excess.  As  we  have  seen,  the

cumulative  CO 2 ­emissions  budget  consis­

tent with a 50­50 chance of meeting the 2°C

goal is 3.7trn tonnes. The budget for 1.5°C is

just  2.9trn  tonnes.  With  2.4trn  tonnes  al­

ready emitted, that leaves a decade of emis­

sions  at  today's  rates  for  1.5°C,  maybe  25

years for 2°C. 

Those  constraints  could  be  eased  if

some  of  what  has  already  been  “spent”

were repaid—that is, if CO 2 were pulled out

of the atmosphere faster than it were being

put in, producing net­negative emissions.

Removing a billion tonnes of carbon diox­

ide in 2050 is not quite the same as not hav­

ing  emitted  it  in  1950,  but  it  is  close.  And

this  remains  true  even  if  the  removal

comes  after  the  budget  has  been  broken.

Carbon budgets can be overshot, at least for a while.

This  offers  rich  countries  that  benefited  disproportionately

from 20th­century emissions a way to create room in the budget

for poor ones which were left out. But to do this on an appreciable

scale they need to draw down huge amounts of carbon. Some sce­

narios have negative emissions of well over 10gt a year—a global

fossil­fuel  industry  running  in  reverse.  Done  through  dacthat

would require huge capital investment and use up a great deal of

clean, renewable but still not free energy in the process.

This would not have to be done entirely through dac. Nature

takes  half  the  carbon  dioxide  that  humans  put  into  the  atmo­

sphere back out, through either photosynthesis or geochemistry.

Both processes could be ramped up.

For  photosynthesis,  more  trees  are  the  obvious  option.  They

can  be  grown  in  plantations,  including  commercial  ones  where

new trees replace each year’s harvest; or they can be encouraged in

regenerated forests. The second option is much better. A study in

2019  found  that  over  80  years  restoring  natural  forests  stores  an

average  of  40  times  more  carbon  per  hectare  than  new  planta­

tions.  Restoration  also  scores  better  in  preserving  biodiversity.

But  plantations  make  money  in  an  easily  understood  way.  The

same  study  found  that  45%  of  commitments  made  under  the

Bonn  Challenge,  a  voluntary  ngo­led  initiative  to  boost  forests,

involved planting poor­quality commercial plantations.

Another option is to raise the amount of carbon stored in agri­

cultural land and forests that are already commercially exploited.

So­called “nature­based solutions” along these lines are staples of

the market for voluntary carbon offsets, where vendors promise to

do things like growing trees, or stopping them being cut down, to

absolve clients’ sins of emission.

Offsetting schemes seem able to deliver negative emissions at

a reasonable price. When Microsoft and Stripe, a fintech company,