Pol­lu­tion of a dif­fer­ent kind

Hu­man-in­duced ni­tro­gen emis­sions have sur­passed nat­u­ral emis­sions, dam­ag­ing health and the en­vi­ron­ment

Down to Earth - - CONTENTS - SHREESHAN VENKATESH | NEW DELHI

Ar­ti­fi­cial ni­tro­gen has ex­ceeded nat­u­ral emis­sions, lead­ing to alarm­ing lev­els of ni­tro­gen pol­lu­tion

Fpast 40 years, Ramesh OR THE Ku­mar, a farmer in Murthal vil­lage in Haryana’s Soni­pat dis­trict, has been ap­ply­ing 200 kg of urea in a year on ev­ery hectare (ha) of his land. Ku­mar, who grows rice and wheat, says the yield has been more or less the same ev­ery year. But he ad­mits that he can­not think of farm­ing with­out urea. “With only or­ganic ma­nure, I will grow noth­ing,” he says.

Ku­mar’s use of urea re­flects In­dia’s in­creas­ing de­pen­dence on ar­ti­fi­cial ni­tro­gen fer­tilis­ers. In­dian Fer­tiliser Sce­nario 2014, an an­nual pub­li­ca­tion of the depart­ment of fer­tilis­ers un­der the Min­istry of Chem­i­cals and Fer­tilis­ers, states that the use of urea in the coun­try has in­creased by more than 50 per cent since 2000—the per hectare con­sump­tion of ni­tro­gen is at least 100 kg in eight In­dian states, in­clud­ing Bi­har, Punjab, Haryana, Ut­tarak­hand, Ut­tar Pradesh, un­di­vided Andhra Pradesh, Tamil Nadu and Puducherry.

But In­dia is not alone. Dur­ing the past cen­tury, the global con­sump­tion of ni­tro­gen has seen a steady in­crease.In 1980,de­vel­oped coun­tries ac­counted for 70 per cent of the world’s to­tal ni­tro­gen con­sump­tion. By 2010, it was the de­vel­op­ing coun­tries which ac­counted for 70 per cent of the global ni­tro­gen con­sump­tion. In­dia is the sec­ond- high­est con­sumer of ni­tro­gen in the world af­ter China. Ac­cord­ing to the Food and Agri­cul­ture Or­ga­ni­za­tion, China’s an­nual con­sump­tion of ni­tro­gen is 44.97 mil­lion tonnes, while In­dia con­sumes 16.48 mil­lion tonnes—four times more than Brazil’s an­nual con­sump­tion of 4.25 mil­lion tonnes.

The in­creas­ing rate of ni­tro­gen use by hu­mans has led to an im­bal­ance in the ni­tro­gen con­tent in the en­vi­ron­ment. Ac­cord­ing to “Our Nu­tri­ent World”,a 2013 re­port of the United Na­tions En­vi­ron­ment Pro­gramme (unep), hu­man-in­duced ni­tro­gen in­puts or fer­tilis­ers and as­so­ci­ated emis­sions from agri­cul­ture, fos­sil fuel burn­ing, sewage and in­dus­trial waste have

di­rectly or in­di­rectly far sur­passed nat­u­ral emis­sions, caus­ing ni­tro­gen pol­lu­tion that has reached alarm­ing lev­els. A study pub­lished in the jour­nal En­vi­ron­men­tal Re­search Letters in June this year shows that the an­nual eco­nomic loss in the US due to energy wastage and dam­ages to the en­vi­ron­ment and hu­man health from ni­tro­gen pol­lu­tion is $210 bil­lion. “Our Nu­tri­ent World” es­ti­mated that the global cost of dam­age from ni­tro­gen could go up to US $2,000 bil­lion.

Sim­i­lar stud­ies are not avail­able for In­dia. The threats posed by ni­tro­gen pol­lu­tion are in­di­vid­u­ally and col­lec­tively a huge prob­lem for the global so­ci­ety to­day, says M A Sut­ton, lead au­thor of the unep re­port (see ‘We can man­age ni­tro­gen...’, p42).

From nu­tri­ent to pol­lu­tant

Ni­tro­gen, which is a vi­tal macronu­tri­ent for most plants, is the most abun­dant el­e­ment in the at­mos­phere. A lit­tle over 78 per cent of dry air on Earth is ni­tro­gen.But at­mo­spheric ni­tro­gen, or dini­tro­gen, is un­re­ac­tive and can­not be utilised by plants di­rectly. Un­til the be­gin­ning of the 20th cen­tury, farm­ers de­pended on a nat­u­ral process called ni­tro­gen fix­a­tion for the con­ver­sion of at­mo­spheric ni­tro­gen into re­ac­tive ni­tro­gen in the soil: ni­tro­gen-fix­ing bac­te­ria like rhi­zo­bia live sym­bi­ot­i­cally with legu­mi­nous plants, pro­vid­ing ni­tro­gen to the plant and soil in the form of re­ac­tive com­pounds like am­mo­nia and ni­trate.

But the nat­u­ral ni­tro­gen cy­cle was in­ad­e­quate to feed the grow­ing pop­u­la­tion. Sci­en­tists Fritz Haber and Carl Bosch

solved this prob­lem by pro­duc­ing am­mo­nia by com­bin­ing at­mo­spheric ni­tro­gen with hy­dro­gen gas at high tem­per­a­ture and pres­sure—known as the Haber-Bosch process. The Green Revo­lu­tion, which was in­stru­men­tal in es­tab­lish­ing food se­cu­rity in the de­vel­op­ing coun­tries in the 1960s, was driven by ar­ti­fi­cial ni­tro­gen-fix­a­tion. To­day, about half of the world’s pop­u­la­tion de­pends on this process for its nutri­tion.

But over 80 per cent of the ni­tro­gen in soil is not utilised by hu­mans (see ‘What goes down comes up’, p40). While over four-fifths of the ni­tro­gen is used to feed live­stock, only about six per cent reaches hu­mans in case of non-veg­e­tar­ian diet, as com­pared to the 20 per cent that reaches the plate of a veg­e­tar­ian.

Ni­tro­gen be­comes a pol­lu­tant when it es­capes into the en­vi­ron­ment and re­acts with other or­ganic com­pounds.It is ei­ther re­leased into the at­mos­phere, gets dis­solved in wa­ter sources such as rivers, lakes or ground­wa­ter, or re­mains in the soil. While it might lead to favourable growth of species that can utilise this nu­tri­ent, ni­tro­gen as a pol­lu­tant is of­ten detri­men­tal to the en­vi­ron­ment and health (see ‘Ne­far­i­ous ni­tro­gen’). Ac­cord­ing to the World Health Or­ga­ni­za­tion, ni­trate-con­tam­i­nated drink­ing wa­ter can cause re­duced blood func­tion, can­cer and en­demic goi­ters (see ‘Pol­lu­tants and ef­fects’, p40). Sur­plus in­puts of ni­tro­gen com­pounds have been found to cause soil acid­i­fi­ca­tion. The low­er­ing pH, as a re­sult of the acid­i­fi­ca­tion, can lead to nu­tri­ent dis­or­ders and in­creased tox­i­c­ity in plants. It may also af­fect nat­u­ral soil de­com­po­si­tion. Quite a few stud­ies have been con­ducted on the ef­fi­ciency of ni­tro­gen fer­tiliser and the gen­eral con­clu­sion is that its use de­creases soil fer­til­ity, says Ta­pan Ad­hya, pro­fes­sor at the School of Biotech­nol­ogy in the Kalinga In­sti­tute of In­dus­trial Tech­nol­ogy, Bhubaneswar, Odisha.

“Ni­tro­gen is cen­tral to In­dia’s food pro­duc­tion, but its use in our agri­cul­ture sys­tem has put us in a Catch-22 sit­u­a­tion. We can­not pro­duce enough food to feed the na­tion with­out ni­tro­gen, but at the same time we can­not keep in­tro­duc­ing higher quan­ti­ties of ni­tro­gen be­cause of its pol­lut­ing ef­fects,” says N Raghu­ram,

di­rec­tor of the South Asian Cen­tre of In­ter­na­tional Ni­tro­gen Ini­tia­tive, a group of sci­en­tists and re­searchers work­ing to im­prove ni­tro­gen ef­fi­ciency.

Man­age­ment is the key

The chal­lenge for the cur­rent cen­tury is to op­ti­mise the uses of nutri­tion while min­imis­ing the neg­a­tive im­pacts, notes James Gal­loway, a pro­fes­sor at the Univer­sity of Vir­ginia, the US, who is re­search­ing on the ef­fects of re­ac­tive ni­tro­gen. As the prob­lem of ni­tro­gen pol­lu­tion starts to gain global at­ten­tion, there have been in­no­va­tions aimed at im­prov­ing its ef­fi­ciency by op­ti­mis­ing us­age. Eight corn farms in Mary land, the US, have been ex­per­i­ment­ing with sen­sor tech­nol­ogy, which col­lects, in real time, data about the quan­tity of ni­tro­gen plants need.

A sim­pler method of re­duc­ing ni­tro­gen ap­pli­ca­tion is pre­ci­sion farm­ing where small quan­ti­ties of ni­tro­gen are ad­min­is­tered rou­tinely in­stead of large doses ap­plied uni­formly over the field. Sim­i­larly, tablets and coated forms of ni­tro­gen, when ap­plied at the root level, re­lease nu­tri­ents slowly. “Bangladesh has man­aged to in­crease the ef­fi­ciency of nutri­tion up­take by plants by ap­ply­ing fer­tilis­ers through tablets. A sim­i­lar at­tempt is be­ing made with neem- coated urea in In­dia,” Ad­hya says (see ‘ Neem- coated growth’, Down To Earth, July 1-15,2015).Sup­ple­mented with or­ganic fer­tilis­ers and com­bined with op­ti­mal tim­ing of ap­pli­ca­tion, sow­ing and wa­ter­ing, these meth­ods have shown marked im­prove­ment over tra­di­tional ef­fi­cien­cies of ni­tro­gen. Europe, which has used such meth­ods in its agri­cul­ture, has at­tained the high­est ni­tro­gen use ef­fi­ciency in the world, ac­cord­ing to the Or­ga­ni­za­tion for Eco­nomic Co­op­er­a­tion and De­vel­op­ment (oecd).

Raghu­ram says ni­tro­gen pol­lu­tion is an is­sue of im­proper man­age­ment rather than in­abil­ity. “The costs of abat­ing ni­tro­gen pol­lu­tion would be much less than the ben­e­fits to health and en­vi­ron­ment. A 20 per cent in­crease in the rate of ef­fi­ciency would save an es­ti­mated 20 mil­lion tonnes of re­ac­tive ni­tro­gen by 2020, which equates to an im­prove­ment in hu­man health, bio­di­ver­sity and cli­mate worth US $170 bil­lion,” Sut­ton ex­plains.

De­vel­oped re­gions such as the US and Europe have pub­lished de­tailed re­ports about ni­tro­gen us­age and pol­lu­tion. But In­dia is nowhere close to ag­gre­gat­ing some­thing sim­i­lar of its own, says Y P Abrol, founder of the non-profit In­dian Ni­tro­gen Group. “For over a decade we have been try­ing to con­vince var­i­ous min­istries deal­ing with ni­tro­gen to take up data col­lec­tion and a de­tailed plan of ac­tion. But there has been no con­certed pol­icy or reg­u­la­tion,” he adds.

VIKAS CHOUDHARY / CSE A farmer in Haryana pre­pares to

add urea to his wheat crop

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