Dou­ble trou­ble

Over­looked but po­tent, ni­trous ox­ide is a risk to the ozone layer and the global cli­mate.

The Star Malaysia - Star2 - - ECOWATCH -

EMIS­SIONS of ni­trous ox­ide (N2O), an of­ten over­looked yet po­tent gas, could nearly dou­ble by 2050 and thus po­ten­tially un­der­mine gains in the ozone layer re­cov­ery and ex­ac­er­bate cli­mate change.

Draw­ing Down N2O To Pro­tect Cli­mate And

The Ozone Layer, a new re­port by the UN En­vi­ron­ment Pro­gramme (UNEP), warns that ni­trous ox­ide is now the most im­por­tant ozone-de­plet­ing emis­sion and the third most po­tent green­house gas re­leased into the at­mos­phere. While N2O ex­ists nat­u­rally in the at­mos­phere in trace amounts, hu­man ac­tiv­i­ties have in­creased its con­cen­tra­tions since the in­dus­trial rev­o­lu­tion.

The UNEP re­port, pro­duced in con­junc­tion with sci­en­tists and ex­perts from more than 35 or­gan­i­sa­tions, points out that re­duc­ing N2O emis­sions has ma­jor cost ben­e­fits since emis­sions are con­nected to di­verse eco­nomic sec­tors from agri­cul­ture, chem­i­cal man­u­fac­tur­ing and elec­tric­ity pro­duc­tion to waste man­age­ment, trans­porta­tion and fish pro­duc­tion. Gains from emis­sions re­duc­tion will in­clude in­creased crop and live­stock pro­duc­tiv­ity, poverty al­le­vi­a­tion, im­proved hu­man health and re­duced en­vi­ron­men­tal degra­da­tion.

An ear­lier study quoted by the re­port in­di­cated that an across-the-board im­prove­ment in ni­tro­gen use ef­fi­ciency of 20% would cost around US$12bil (RM36­bil) an­nu­ally, but would save around US$23bil (RM69­bil) in an­nual fer­tiliser costs alone. Ad­di­tional en­vi­ron­men­tal, cli­mate and hu­man ben­e­fits could be worth an es­ti­mated US$160bil (RM480­bil) per an­num.

“Al­though not as preva­lent in the at­mos­phere as CO2 in terms of mass, N2O, com­monly known to many as ‘ laugh­ing gas’, is far from a laugh­ing mat­ter with re­spect to cli­mate and ozone dam­age, as it has a dis­pro­por­tion­ate im­pact on global warm­ing be­cause of its ra­dia­tive prop­er­ties and long life­time in the at­mos­phere, which is 120 years on av­er­age. Ac­tion on th­ese emis­sions of­fer yet another op­por­tu­nity to keep the world un­der a 2°C tem­per­a­ture rise,” said UNEP ex­ec­u­tive di­rec­tor Achim Steiner.

Most of the de­ple­tion of the strato­spheric ozone layer up to now has been due to the in­fa­mous chlo­roflu­o­ro­car­bons (CFCs) and other halo­genated (chlo­rine- and brominecon­tain­ing) chem­i­cals. How­ever, th­ese chem­i­cals – un­like N2O – are now widely con­trolled by the Mon­treal Pro­to­col, an in­ter­na­tional treaty de­signed to pro­tect the ozone layer.

Main sources

Agri­cul­ture is by far the largest source of hu­man-in­duced N2O emis­sions, ac­count­ing for two-thirds of th­ese emis­sions. Mean­while, other im­por­tant sources of N2O in­clude in­dus­try and fos­sil fuel com­bus­tion, biomass burn­ing and waste­water. The re­port lists spe­cific, ac­tion­able mea­sures that can be taken in each of th­ese ar­eas:

> Agri­cul­tural emis­sions: Emis­sions can be re­duced by boost­ing the ef­fi­ciency of ni­tro­gen use in agri­cul­ture. This means im­prov­ing the abil­ity of crops and live­stock to bet­ter utilise ni­tro­gen, and min­imis­ing the loss of ni­tro­gen to the en­vi­ron­ment that oc­curs dur­ing crop cul­ti­va­tion and an­i­mal pro­duc­tion. Re­duc­ing food waste and loss, as well as con­sum­ing less meat – the pro­duc­tion of an­i­mal pro­tein leads to higher N2O emis­sions than plant pro­tein – are other op­tions for re­duc­ing agri­cul­tural emis­sions of N2O.

> In­dus­trial emis­sions: The re­port sug­gests that sig­nif­i­cant gains can be achieved by con­trol­ling emis­sions from just two chem­i­cal in­dus­tries – adipic acid and ni­tric acid – which ac­count for about 5% of global N2O emis­sions. Such re­duc­tions can be achieved

by in­stalling emis­sions con­trol equip­ment in fa­cil­i­ties pro­duc­ing such chem­i­cals.

> Emis­sions from biomass burn­ing: The re­port notes that N2O emis­sions from land­scape fires can be achieved by re­duc­ing the use of fires for for­est clear­ing and im­ple­ment­ing pre­scribed burn­ing to re­duce the amount of burn­able veg­e­ta­tion in nat­u­ral fires. Im­prov­ing the fuel and com­bus­tion ef­fi­ciency of stoves can re­duce emis­sions from biomass­burn­ing in house­hold stoves.

> Emis­sions from waste­water and aqua­cul­ture: Proper col­lec­tion and treat­ment of waste­water can re­duce N2O emis­sions to the at­mos­phere. Th­ese in­clude im­proved waste-

wa­ter treat­ment, re­duc­ing waste­water leak­age from sewage pip­ing, and re­cy­cling nu­tri­ents in waste­water as fer­tiliser. Emis­sions from aqua­cul­ture can be low­ered by boost­ing over­all ni­tro­gen use ef­fi­ciency, and by im­ple­ment­ing fish farm­ing sys­tems that re­duce the amount of waste gen­er­ated, or by treat­ing ef­flu­ents from fish ponds.

Over­com­ing bar­ri­ers

Cost, ca­pac­ity build­ing, tech­nol­ogy trans­fer, and the lack of know-how are among the bar­ri­ers to im­ple­ment­ing N2O re­duc­tion strate­gies at a global scale.

Pos­si­ble ac­tions to over­come such bar­ri­ers in­clude: re­mov­ing sub­si­dies that en­cour­age the overuse or mis­use of ni­tro­gen fer­tiliser while pro­vid­ing in­cen­tives for adopt­ing best man­age­ment prac­tices that would im­prove ni­tro­gen use ef­fi­ciency; putting a price tag on ni­tro­gen pol­lu­tion through ap­pro­pri­ate levies, in­cen­tives and trad­able per­mits; en­cour­ag­ing re­search and de­vel­op­ment in tech­niques that en­hance ni­tro­gen use ef­fi­ciency and crop pro­duc­tiv­ity; sup­port­ing good nu­tri­ent man­age­ment prac­tices in crop and live­stock op­er­a­tions; and set­ting tar­gets for N2O emis­sion re­duc­tions and putting in place strate­gies for track­ing progress.

Re­duc­ing N2O emis­sions will also help pro­tect the ozone layer. Ris­ing lev­els of N2O may un­der­mine the gains in ozone layer re­cov­ery achieved by draw­ing down CFC and other ozone-de­plet­ing sub­stances. Re­duc­ing emis­sions will help avoid the con­tin­ued de­ple­tion of the ozone layer and se­cure the gains made by the Mon­treal Pro­to­col. – UNEP

Down­load the re­port at http://www.unep. org/pub­li­ca­tions/ebooks/UNEPN2Ore­port/.

Harm­ful emis­sions: a farmer har­vest­ing cab­bage in a farm in the out­skirts of Hanoi, Viet­nam. Use of fer­tiliser in agri­cul­ture re­leases ni­trous ox­ide, both an ozone-de­plet­ing and green­house gas.

Sewage is pro­cessed in an aer­a­tion tank in the Shatin Sewage Treat­ment Works in the new Ter­ri­to­ries, Hong Kong’s largest sewage treat­ment fa­cil­ity. Thor­ough pro­cess­ing of waste­water will pre­vent emis­sions of ni­trous ox­ide.

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