half the environmental impact of a loaf of bread comes from the
"unsustainable use" of fertilisers on wheat crops,researchers said.
fertilisers boost yields, but they contain or generate chemicals --
ammonia, nitrates, methane and carbon dioxide, among others -- that
drive global warming, they reported in the journal Nature Plants.
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 lead 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 so-called "dead zones"
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
key part of this challenge is resolving the major conflict embedded
in an agri-food system whose primary purpose is to make money, not to
provide sustainable global food security," (our emphasis) the study said.
production and consumption are responsible for about one-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. To better assess the
environmental cost of wheat production, researchers led by Goucher
broke down the supply chain of a typical 800-gram (28-ounce) loaf of
bread from "seed to feed". In 2016, Europeans consumed, on
average, about 63 kilos of bread per person, while Americans eat
about half that amount. They found that ammonium nitrate fertiliser
contributes 43 percent of the greenhouse gas emissions in a loaf's
life cycle, a level they described as "unsustainable." In
agriculture, more than 100 million tonnes of chemical fertiliser is
used globally every year, applied to about 60 percent of all
is a massive problem," said the study's senior author, Peter
Horton, chief research advisor to the Grantham Centre for Sustainable
Futures. "But environmental impact is not costed within the
system, so there are currently no real incentives to reduce our
reliance on fertiliser."
How to achieve sustainable global food security is not only a technical question but a political and economic one, (our emphasis) the researchers added.