The stub­born task of sav­ing the world from cli­mate change

Daily Trust - - IT WORLD -

For the past fif­teen or so years, there have been con­certed global ef­forts to re­duce the con­cen­tra­tions in the at­mos­phere of the so-called green­house gases, since they con­trib­ute to the green­house ef­fect by ab­sorb­ing so­lar ra­di­a­tion that have bounced off the earth’s sur­face and emit­ting this back to earth, lead­ing to rel­a­tive global warm­ing. With­out this, ra­di­a­tion in­ci­dent on the earth sur­face would es­cape into space. Ex­am­ples of green­house gases in­clude wa­ter va­por, car­bon diox­ide, meth­ane, ni­trous ox­ide, ozone, chlo­roflu­o­ro­car­bons (CFCs), and hy­droflu­o­ro­car­bons (such as HCFCs and HFCs).

The rel­a­tive amount of the emis­sion of the gases by the US in 2016 is as fol­lows: car­bon diox­ide (81%), meth­ane (10%), ni­trous ox­ide (6%) and flu­o­ri­nated gases (3%). (Note that al­though wa­ter va­por is more abun­dant than these other species, it is not in­tro­duced into the at­mos­phere by hu­mans.) Also note that with­out green­house gases the av­er­age tem­per­a­ture of the sur­face of the earth would be ap­prox­i­mately equal to ™18°C (0°F), as op­posed to the nor­mal av­er­age of 15°C (59°F).

Car­bon diox­ide en­ters the at­mos­phere through the burn­ing of fos­sil fu­els such as coal, nat­u­ral gas, and oil; as well as from solid waste, trees and wood prod­ucts, and also as a re­sult of cer­tain chem­i­cal re­ac­tions (e.g., man­u­fac­ture of ce­ment). Car­bon diox­ide is re­moved from the at­mos­phere when it is con­sumed by plants as part of pho­to­syn­the­sis. Meth­ane is also emit­ted dur­ing the pro­duc­tion of coal, nat­u­ral gas, and oil. In ad­di­tion, meth­ane emis­sions re­sult from live­stock and other agri­cul­tural prac­tices and by the de­cay of or­ganic waste in mu­nic­i­pal solid waste land­fills. Ni­trous ox­ide is emit­ted dur­ing agri­cul­tural and in­dus­trial ac­tiv­i­ties, and dur­ing the com­bus­tion of fos­sil fu­els and solid waste. Hy­droflu­o­ro­car­bons, per­flu­o­ro­car­bons, sul­fur hex­aflu­o­ride, and ni­tro­gen tri­flu­o­ride are syn­thetic, pow­er­ful green­house gases that are emit­ted from a va­ri­ety of in­dus­trial pro­cesses.

Ac­cord­ing to a Wikipedia en­try, hu­man ac­tiv­i­ties since the be­gin­ning of the In­dus­trial Rev­o­lu­tion (around 1750) have pro­duced a 40% in­crease in the at­mo­spheric con­cen­tra­tion of car­bon diox­ide, from 280 parts per mil­lion (ppm) in 1750 to 406 ppm in early 2017. This in­crease has oc­curred de­spite the up­take of more than half of the emis­sions by var­i­ous nat­u­ral "sinks" in­volved in the car­bon cy­cle. The vast ma­jor­ity of car­bon diox­ide emis­sions come from the com­bus­tion of fos­sil fu­els, with ad­di­tional con­tri­bu­tions com­ing from de­for­esta­tion, changes in land use, soil ero­sion and agri­cul­ture (in­clud­ing live­stock).

What is im­por­tant in this ar­ti­cle is to note that the fail­ure to keep the con­cen­tra­tion of car­bon diox­ide in the at­mos­phere in check will lead to ever in­creas­ing global tem­per­a­tures, which will threaten the ex­is­tence of life on earth. So, it is im­per­a­tive for us to con­trol not just the in­crease of the con­cen­tra­tion of car­bon diox­ide in the at­mos­phere, but to also re­move a sig­nif­i­cant por­tion of what is al­ready present.

The Paris Agree­ment of 2015 - signed by 175 coun­tries in New York in 2016 - aims to strengthen the global re­sponse to the threat of cli­mate change by keep­ing a global tem­per­a­ture rise this cen­tury to well below 2 de­grees Cel­sius above pre-in­dus­trial lev­els and to pur­sue ef­forts to limit the tem­per­a­ture in­crease even fur­ther to 1.5 de­grees Cel­sius. How­ever, at cur­rent car­bon diox­ide emis­sion rates, ex­perts have re­cently re­ported that tem­per­a­tures could in­crease be­yond 2 °C, which the United Na­tions' In­ter­gov­ern­men­tal Panel on Cli­mate Change (IPCC) des­ig­nated as the up­per limit to avoid dan­ger­ous lev­els by 2036.

Rchard Con­niff in the Jan­uary 2019 is­sue of the Sci­en­tific Amer­i­can mag­a­zine goes into some de­tails on the costs and ef­fec­tive­ness of the var­i­ous strate­gies that are be­ing in­ves­ti­gated for car­bon cap­tur­ing. These tech­niques in­clude bioen­ergy car­bon cap­ture and stor­age, biochar, en­hanced weath­er­ing, di­rect air cap­ture, ocean fer­til­iza­tion, and soil car­bon se­ques­tra­tion. To il­lus­trate two of these tech­niques, di­rect air cap­ture uses ma­chines to pull in am­bi­ent air, chem­i­cally sep­a­rat­ing out car­bon diox­ide and pump­ing it un­der­ground for per­ma­nent stor­age. In en­hanced weath­er­ing, rock is pul­ver­ized into dust, which can draw car­bon diox­ide from the air to fer­til­ize soil when spread on fields. When the dust is sprin­kled on the ocean, it re­acts with sea­wa­ter to con­vert car­bon diox­ide into car­bon­ates which set­tle on the ocean floor.

No sat­is­fac­tory so­lu­tions have yet been found among the seven car­bon diox­ide cap­tur­ing tech­niques dis­cussed. In par­tic­u­lar, the po­ten­tial car­bon diox­ide that can be re­moved sub­stan­tially falls short of the cost of re­moval. For ex­am­ple, it could be that a par­tic­u­lar tech­nique re­quires too much (green) so­lar or wind power, suf­fi­cient to be put on a grid and en­abling the turn­ing off of a coal plant! More­over, nu­mer­ous neg­a­tive side ef­fects have been iden­ti­fied, such as air pol­lu­tion, bio­di­ver­sity, food se­cu­rity, ground and wa­ter pol­lu­tion, soil qual­ity prob­lems, po­ten­tial car­bon diox­ide leak­age, and so on. Also, be­cause some of the meth­ods dis­cussed com­pete for the same re­sources, you can­not just add up the po­ten­tial of the meth­ods.

In gen­eral, cor­po­ra­tions have been re­luc­tant to in­vest in car­bon diox­ide re­moval tech­nolo­gies since they see no clear busi­ness case. That is, they see the whole idea as pub­lic (so­cial) ben­e­fit.

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