Bread is a staple of many people’s diet, and in the UK alone, an estimated 12 million loaves are sold daily! However, researchers from the University of Sheffield have recently been analyzing the environmental impact of producing a loaf of bread: from growing and harvesting the wheat at the farm; milling the grain; producing the flour; baking the bread and the production of the final product, ready to be sold by retailers at shop shelves.

The verdict, published in the journal Nature Plants, is that ammonium nitrate fertiliser used in wheat cultivation contributes almost half of the greenhouse gas emissions.

How Greenhouse Gases Are Released During Production

The study shows that the use of ammonium nitrate fertilizer used in wheat cultivation contributes an estimated 43 % of the greenhouse gas emissions.

Dr Liam Goucher, from the University of Sheffield who carried out the study, said, “Consumers are usually unaware of the environmental impacts embodied in the products they purchase – particularly in the case of food, where the main concerns are usually over health or animal welfare. There is perhaps awareness of pollution caused by plastic packaging, but many people will be surprised at the wider environmental impacts revealed in this study. We found in every loaf there is embodied global warming resulting from the fertiliser applied to farmers’ fields to increase their wheat harvest. This arises from the large amount of energy needed to make the fertilizer and from nitrous oxide gas released when it is degraded in the soil.”

Today, an estimated 60% of agricultural crops are now grown with the use of fertilizers. While they can help boast the growth of plants and vegetables (to assist the growing demand of food yields), these fertilizers consist of substances and chemicals such as methane, carbon dioxide, ammonia and nitrogen, and the emissions from these substances contribute to greenhouse gases.


Food-Security Challenge

Professor Peter Horton FRS, Chief Research Advisor to the Grantham Centre for Sustainable Futures at the University of Sheffield, said: “Our findings bring into focus a key part of the food security challenge – resolving the major conflicts embedded in the agri-food system, whose primary purpose is to make money not to provide sustainable global food security. High agricultural productivity – necessary for profit for farmers, agri-businesses and food retailers, whilst also keeping prices low for consumers – currently requires high levels of application of relatively cheap fertilizers.”

Horton went on to add that over 100 million tons of fertilizer are used globally each year to support agricultural production, with the environmental impact not costed within the system.


One of the biggest challenges of the 21st century is figuring out how to produce sufficient healthy and affordable food for the world’s growing and more demanding population, whilst protecting the environment. Solutions to reduce the impact include improved agronomic practices (i.e. organic farming, new technologies to monitor the nutritional status of soils and plants, recycling waste).

A small change could have a huge impact here! Bread for your head indeed.

Source: Sheffield University

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