Bread: rich in vitamins, minerals – and carbon dioxide

A team of scientists from the University of Sheffield in the UK has earned its dough by tracing the process of bread manufacturing from start to finish, finding that every 800 gram wholegrain loaf produced in the UK produces 0.589 kilograms of carbon dioxide.

Published in Nature Plants, the study shows that over 40% of the environmental impact of the bread production process comes solely from the use of ammonium nitrate fertilisers.

With food production and consumption accounting for one-third of the planet’s total greenhouse gas emissions, the study highlights the dependence of the bread market on unsustainable fertiliser use. It indicates that if we hope to achieve sustainable food production for our future population projection of 10 billion all actors in the supply chain need to assume responsibility.  

The scientists say the study “exposes an unresolved grand challenge for the twenty-first century: how to produce more food but with lower pollution”.

The team, led by Liam Goucher of the university’s Advanced Resource Efficiency Centre, needed to first breakdown the bread-making process in order to assess which components were having the largest environmental impact.

Breaking research bread with commercial bakers, flour producers, and an agronomy services provider, the scientists monitored the bread making process from beginning to end.

Three distinct stages of the supply chain – wheat cultivation, milling, and baking – were subdivided into 14 designated processes, and each measured for its material and energy flow.

Global warming potential was measured via the calculated emission of green-house gases, while capacity for water pollution and potential human health consequences were also considered.

In all three categories, wheat cultivation was shown to be the major culprit – accounting for over half of the negative environmental impact – with fertiliser use the largest single process contributing to environmental harm.

The researchers pointed to some positive changes that have been made in the industry, noting that a switch to low-density polyethylene wrapping.

The use of fertilisers in bread-making represents a catch-22. Without them, there is lower wheat yield, meaning the price of bread rises; with them, negative environmental impacts increase.

The most immediate solution, according to the researchers, is a combination of improved agricultural practice and crop plant physiology.

The team recommends at the very least a more selective application of fertilisers, adding that “more radical is a shift away from chemical fertiliser altogether towards a biological approach”.

The researchers also recommend crop rotations with nitrogen-fixing legumes, and the development of new wheat varieties with an increased ability to take up nitrogen from the soil.