EMIS­SIONS Ki­wis put the heat on emis­sions

With al­most half of New Zealand’s green­house gas emis­sions com­ing from the agri­cul­tural sec­tor, the re­search be­ing con­ducted in this field is vi­tal – and has global ap­pli­ca­tions.

Element - - Planet - HARRY CLARK Harry Clark is the di­rec­tor of the New Zealand Agri­cul­tural Green­house Gas Re­search Cen­tre (NZAGRC) and co-chair of the Live­stock Re­search Group of the Global Re­search Al­liance for Green­house Gases. He is a lead author for the In­ter­na­tional Pa

Green­house gases (GHG) are es­sen­tial for life on earth. Al­though they make up only a small frac­tion of our at­mos­phere, due to their “heat trap­ping” abil­ity they rep­re­sent the dif­fer­ence be­tween the world be­ing an al­most life­less planet of mi­nus 19°C and the com­par­a­tively com­fort­able one we live in to­day of about 14°C. How­ever, it is pos­si­ble to have too much of a good thing and there is now ro­bust sci­en­tific ev­i­dence that the cli­mate is chang­ing, and that most of the warm­ing ob­served over the past 50 years is due to in­creas­ing GHG con­cen­tra­tions in the at­mos­phere aris­ing from hu­man ac­tiv­i­ties.

Agri­cul­ture, in com­mon with other in­dus­tries, emits GHG in the form of CO2 aris­ing from the burn­ing of fos­sil fu­els for the run­ning of farm ve­hi­cles and ma­chin­ery and elec­tric­ity gen­er­a­tion. How­ever, agri­cul­ture’s largest source of emis­sions are in the form of meth­ane (CH4 ) and ni­trous ox­ide (N2 O) aris­ing from rais­ing live­stock and grow­ing crops. Meth­ane is emit­ted from the mouths of an­i­mals as a by-prod­uct of the di­ges­tion of feed, from the stor­age and han­dling of an­i­mal wastes and from rice pro­duc­tion. Ni­trous ox­ide is emit­ted when ni­tro­gen-con­tain­ing fer­tilis­ers and ma­nures are spread on the land and from urine patches de­posited on land by graz­ing an­i­mals. World­wide it is es­ti­mated that about 13% of all hu­man pro­duced GHG emis­sions arise from agri­cul­tural emis­sions of CH4 and N2 O.

New Zealand is in a unique po­si­tion among de­vel­oped coun­tries in that its econ­omy is still heav­ily in­flu­enced by agri­cul­ture, par­tic­u­larly pas­toral agri­cul­ture; in 2012 the value of ex­ports from the pas­toral sec­tor were $19.7 bil­lion, 42% of to­tal ex­ports. The im­por­tance of the pas­toral agri­cul­tural sec­tor to the New Zealand econ­omy is also re­flected in our GHG emis­sions. Cur­rently agri­cul­ture ac­counts for 47% of New Zealand’s to­tal car­bon diox­ide equiv­a­lent emis­sions and emis­sions have risen by ap­prox­i­mately 12% since 1990. Am­bi­tious out­put tar­gets from the dairy and meat sec­tors sug­gest that emis­sions from agri­cul­ture will con­tinue to rise in the fu­ture.

Agri­cul­tural GHG mit­i­ga­tion re­search

Re­duc­ing CH4 and N2 O from emis­sions agri­cul­ture is sci­en­tif­i­cally chal­leng­ing. They arise from nat­u­ral mi­cro­bial pro­cesses that have mul­ti­ple in­flu­ences, some of which are dif­fi­cult to con­trol. For ex­am­ple, the amount of N2 O emit­ted from urine de­posited on pas­tures by graz­ing an­i­mals is heav­ily in­flu­enced by rain­fall. In ad­di­tion, any con­trol mea­sures can­not be at the ex­pense of re­duc­ing agri­cul­tural

pro­duc­tiv­ity. Meth­ane emit­ted dur­ing the di­ges­tion of feed plays an im­por­tant role in en­sur­ing that the di­ges­tive process works ef­fi­ciently.

In the past ten years suc­ces­sive New Zealand Gov­ern­ments and the agri­cul­tural in­dus­try have in­vested in re­search to re­duce GHG emis­sions. Broadly, the re­search can be di­vided into two types, ‘in­di­rect’ and ‘di­rect’.

“New Zealand soils are high in soil car­bon (150 – 200 tonnes per hectare down to a depth of 30cm) and adding just one tonne per hectare per year would off­set all agri­cul­tural emis­sions an­nu­ally. ”

In­di­rect re­search is re­search de­signed to im­prove the ef­fi­ciency of agri­cul­tural pro­duc­tion, for ex­am­ple breed­ing cows with im­proved milk yields and sheep with bet­ter lamb­ing rates. Al­though not tar­geted at re­duc­ing GHG emis­sions, im­prove­ments in the ef­fi­ciency of pro­duc­tion do in­flu­ence emis­sions as they re­sult in more prod­uct be­ing pro­duced rel­a­tive to the amount of GHG emit­ted. Im­prove­ments in ef­fi­ciency have re­sulted in emis­sions per unit of prod­uct fall­ing by an aver­age of less than 1% per year since 1990, a sub­stan­tial achieve­ment and one that makes New Zealand one of the low­est pro­duc­ers of agri­cul­tural GHG emis­sions per unit of milk and meat pro­duced in the world.

Al­though th­ese achieve­ments are sig­nif­i­cant, they are not enough on their own to re­duce ab­so­lute GHG emis­sions given that in­dus­try tar­gets are to in­crease prod­uct out­put by close to 2% per year. This is where di­rect mit­i­ga­tion re­search comes in. Di­rect re­search aims to re­duce the amount of GHG emit­ted per kg of feed eaten or kg of ni­tro­gen ap­plied, ir­re­spec­tive of the amount of prod­uct pro­duced. Both di­rect and in­di­rect ap­proaches are needed for agri­cul­ture to con­trib­ute to re­duc­tions in ab­so­lute GHG emis­sions.

The New Zealand Agri­cul­tural Green­house Gas Re­search Cen­tre (NZAGRC) fo­cusses its re­search on di­rect emis­sions re­duc­tion. In part­ner­ship with an­other govern­ment in­dus­try en­tity, the Pas­toral Green­house Gas Re­search Con­sor­tium (PGgRc), we fo­cus on re­duc­ing emis­sions of CH4 and N O2 and also on ex­plor­ing whether it is pos­si­ble to off­set th­ese emis­sions by tak­ing CO2 from the at­mos­phere and stor­ing it as sta­ble car­bon in soils.

In the CH4 area our main ef­fort has been in try­ing to re­duce emis­sions aris­ing from the di­ges­tion of feed in ru­mi­nants. The type of feed eaten in­flu­ences the amount of CH4 pro­duced, for ex­am­ple bras­si­cas pro­duce 20% less CH4 than grasses, and an at­trac­tive method of re­duc­ing emis­sions is to change the feed. How­ever, this is not sim­ple in prac­tice in New Zealand when many an­i­mals graze out­doors all year. A more prac­ti­cal ap­proach is to try to sup­press the or­gan­isms that are re­spon­si­ble for pro­duc­ing meth­ane in the an­i­mal. One method be­ing re­searched is to vac­ci­nate an­i­mals so they pro­duce com­pounds in their saliva that can sup­press the growth of the meth­ane pro­duc­ing or­gan­isms. An­other promis­ing area is dis­cov­er­ing safe and ef­fec­tive com­pounds that can be fed in slow-re­lease form to di­rectly re­duce the ac­tiv­ity of th­ese meth­ane emit­ting or­gan­isms. Both of th­ese ap­proaches have pro­gressed through the lab­o­ra­tory stage and are be­ing tested on small num­bers of an­i­mals un­der highly con­trolled con­di­tions.

Ni­trous ox­ide emis­sions from urine patches and ni­tro­gen fer­tiliser ap­pli­ca­tions can be re­duced by the ap­pli­ca­tion of a group of com­pounds called nitri­fi­ca­tion in­hibitors. Var­i­ous types of in­hibitor have been tested and the re­sults are highly promis­ing. Com­bined with man­age­ments de­signed to re­duce the quan­tity of ni­tro­gen ap­plied to soils, es­pe­cially in wet con­di­tions, they of­fer a good tech­ni­cal so­lu­tion. How­ever, for wide­spread up­take their cost needs to come down and they will need to go through the ap­pro­pri­ate prod­uct safety and reg­u­la­tory pro­cesses.

Stor­ing more car­bon in soils is ap­peal­ing as a mit­i­ga­tion ap­proach. New Zealand soils are high in soil car­bon (150 – 200 tonnes per hectare down to a depth of 30cm) and adding just one tonne per hectare per year would off­set all agri­cul­tural emis­sions an­nu­ally. How­ever, al­though the gen­eral prin­ci­ples of how to store more car­bon are known (put more car­bon rich ma­te­rial into the soil), trans­lat­ing this into car­bon that is stored in a sta­ble form is more dif­fi­cult, and cur­rent ev­i­dence sug­gests that some of our highly pro­duc­tive land is ac­tu­ally los­ing soil car­bon. The NZAGRC is un­der­tak­ing a ma­jor on-farm study in the Waikato to ex­plore ways of prac­ti­cally in­creas­ing soil car­bon and early re­sults sug­gest that us­ing plant species that put more car­bon into their roots can in­crease the to­tal amount of soil car­bon stored.

Cli­mate change is a long-term is­sue and ad­dress­ing the driv­ers of cli­mate change, GHG emis­sions, also has to be viewed in the same way. Al­though it is ap­peal­ing to think that a ‘sil­ver bul­let’ so­lu­tion is just around the cor­ner, it is per­haps more re­al­is­tic to think in terms of in­cre­men­tal progress in a num­ber of ar­eas com­bined into ‘bas­kets’ of ap­proaches that can bring about sub­stan­tial re­duc­tions in the long term.

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