Magical thought on fertilizers and climate change

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Opinion

CAMBRIDGE, November 9, 2021 (IPS) – As world leaders wrap up the United Nations Climate Summit in Glasgow, new scientific research shows that there is still a great deal of magical thinking about the contribution of fertilizers to global warming.

Philanthropist Bill Gates nurtured the science retreat in his book How to avoid a climate catastrophe earlier this year. “For me, fertilizer is magic, he admits, nitrogen fertilizer in particular. Under a photo of Gates beaming at a fertilizer distribution warehouse in Yara, Tanzania, he explains that “to grow crops you want tons of nitrogen – far more than you would ever find in a natural environment. [sic]…. But nitrogen makes climate change worse.

That last part, at least, is true, and new research suggests that the climate impacts of excessive nitrogen fertilizer use are much worse than previously estimated. Researchers estimate that the N fertilizer supply chain contributes more than six times the greenhouse gases (GHGs) produced by the entire commercial aviation sector.

Nitrogen: a growing climate problem

By all accounts, food and agriculture are barely on the agenda of the United Nations climate summit, even though food systems contribute about a third of GHGs. Direct emissions from food production account for about a third of this, with the main source being livestock, mainly methane and manure emissions.

But about 10% of direct emissions come from synthetic nitrogen fertilizers applied to crops. Only part of the applied fertilizer is absorbed by the plants. Some of it is transformed into nitrous oxide by microorganisms in the soil. Some escape from the ground or volatilize into gas when applied. The cumulative effect is the release of nitrous oxide, a GHG 265 times more potent than carbon dioxide.

Three scientists in collaboration with Greenpeace, the Institute for Agriculture and Trade Policy and GRAIN carried out the first comprehensive life cycle analysis of N fertilizer emissions. They used improved data on direct emissions in the field and incorporated emissions from the manufacture and transport of nitrogenous fertilizers. Manufacturing, which is heavily dependent on natural gas, accounts for 35% of total nitrogen fertilizer GHGs.

The new estimates, which are preliminary because they are subject to peer review, are 20% higher than those previously used by the United Nations. Unsurprisingly, the biggest emitters are the biggest agricultural producers: China, India, North America and Europe. On a per capita basis, however, the biggest emitters are the major agricultural exporters: the United States, Canada, Brazil, Argentina, Australia, New Zealand and Europe.

Take Africa in the wrong direction

Africa is still not a heavy user of fertilizer, with low application rates – around 15 kg / ha – but increasing rapidly with recent Green Revolution campaigns. As Gates essentially dismisses the climate impacts of fertilizers as a necessary evil to achieve the greater good of food security, it is increasingly evident that the Green Revolution approach is failing on its own terms. My research showed that in AGRA’s 13 target countries, yields were not increasing significantly and the number of undernourished people increased by 31%.

The greatest good promised by AGRA has not been very good.

AGRA is taking Africa in the wrong direction, according to new fertilizer research. Globally, nitrogen fertilizer use is expected to increase by 50 to 138% by 2050. Africa is expected to experience an increase of at least 300% over the next 30 years. It will be much bigger if Gates succeeds.

The climatic implications of this development path are worrying. A 300% increase means 2.7 million tonnes (Mt) more N fertilizer in Africa. With field emissions estimated at 2.65 tonnes of GHGs per tonne of nitrogen and an additional 4.35 tonnes from production and transportation, the total emissions are more like 7 tonnes of GHGs per tonne of nitrogen fertilizer.

By 2050, a 300% increase in fertilizer use in Africa would mean adding about 19 Mt of more GHGs per year than it emits currently. As GHGs accumulate in the atmosphere and nitrous oxide persists for over 100 years, Africa will have contributed an additional 284 Mt of GHGs by 2050 if fertilizer use increases by 300% . If Gates and AGRA are successful and Africa approaches the current global averages of 137 kg / ha of N fertilizer, Africa would contribute 800% more, 50 Mt more in 2050, which is equivalent to emissions from deforestation of half a million hectares of Amazon rainforest (approximately 1.2 million acres). Cumulative GHGs would be 750 Mt by 2050.

This is almost equal to the annual emissions of the entire commercial aviation sector.

“Stupid agriculture for the climate”

Bill Gates is simply wrong when he says that the only way to grow food is to use synthetic fertilizers. Crops need nitrogen and in many areas they can get most or all of what they need through improved agroecological agriculture. Globally, with better nutrient management practices, there could be a 48% reduction in synthetic fertilizer use without reducing grain yields, according to a Nature article.

The scientists who wrote the new report make three recommendations for reducing GHGs associated with the use of nitrogen fertilizers. All question Gates’ green revolution model for Africa:

    • Choose an agricultural model that does not depend on synthetic fertilizers; Intercropping with nitrogen fixing crops has been shown to increase yields and improve soils.
    • Reintegrate livestock into agriculture so that more of the nutrients in manure are returned to the land; less than half are now.
    • Limit the growth of industrial animal production and consumption. Three quarters of nitrogen fertilizers in the world are used to produce animal feed.

The science is clear: African farmers are right when they call the Green Revolution “climate dumb agriculture”.

Timothy A. Sage is Senior Advisor at the Institute for Agriculture and Trade Policy and Senior Researcher at the Global Development and Environment Institute at Tufts University.

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