Weekend Post (South Africa)

Bread’s hidden costs to climate


NEARLY half the environmen­tal impact of a loaf of bread comes from the “unsustaina­ble use” of fertiliser­s on wheat crops, researcher­s said this week.

Synthetic fertiliser­s boost yields, but they contain or generate chemicals – ammonia, nitrates, methane and carbon dioxide – that drive global warming, they reported in the journal Nature Plants.

“This arises from the large amount of energy needed to make the fertiliser, and from nitrous oxide gas released when it is degraded in the soil,” said author Liam Goucher, a scientist at the University of Sheffield in England. Nitrate-rich runoff from industrial-scale agricultur­e also damages lakes, rivers and coastal waters around the world, in some cases creating “dead zones”.

The study highlights a double challenge in the decades ahead: how to grow enough food to feed the world’s population – set to increase to 11 billion from seven billion – in a way that does not poison the planet.

Food production and consumptio­n are responsibl­e for about a third of total greenhouse gas emissions. Cereals such as corn, rice and wheat – usually grown with huge amounts of chemical fertiliser – account for half of the calories consumed by humanity. In 2016 Europeans consumed, on average, about 63kg of bread per person, while Americans eat about half that.

They found that ammonium nitrate fertiliser contribute­s 43% of the greenhouse gas emissions in a loaf’s life cycle, a level they described as “unsustaina­ble”.

In agricultur­e, more than 100 million tons of chemical fertiliser is used every year, applied to about 60% of all agricultur­al crops. – AFP

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