What's the Environmental Impact of a Loaf of Bread?

Researchers were shocked to discover what part of the bread-making process generates most emissions.

Bread has existed in every culture for millennia. Ever since the magical combination of grains plus water and heat was discovered, variations of bread have appeared everywhere, from Middle Eastern pita and Central American tortillas to Ethiopian injera and Canadian bannock. Bread is, quite literally, the staff of life, a staple for the global diet.

That is why researchers at the University of Sheffield in England thought that measuring the carbon footprint of bread would be an effective and interesting exercise. Most analyses of carbon footprints focus on practices like driving cars, heating office buildings, and homes, or even eating meat – but bread? Nobody really talks about it (except in the context of Wheat Belly), but it’s a perfect example of what study author Dr. Liam Goucher describes as a “real-world supply chain.”

Published in Nature Plants, the study focused on every aspect of a loaf of bread’s life cycle, from growing, harvesting, and transporting grain to be milled, to producing flour, shipping to a bakery, baking loaves and packaging them.

Fertilizing a Hefty Amount of Greenhouse Gas

In their life cycle analysis, the researchers found that a loaf of bread emits about a half-kilo of carbon dioxide. Forty-three percent of bread’s greenhouse gas emissions can be attributed to the fertilizers used to grow wheat. Of that percentage, two-thirds of the emissions come from actual fertilizer production, which relies heavily on natural gas.

Goucher, who described the 43-percent figure as “quite a shock,” explained:

“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... 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.”

Other processes, such as tilling the soil, irrigating, harvesting, and using electricity to power mills and bakeries, were also energy-intensive, but they did not amount to nearly as much as fertilizing.

“Farmers typically use more fertilizers than they need to, and not all nitrogen in the fertilizers is used up by plants. Some of the nitrogen goes back into the atmosphere as nitrous oxide, a potent greenhouse gas.” (via NPR)

Agribusiness Needs to Make Changes

It is clear that nitrogen use needs to be reduced significantly – and it can be, through simple strategies like applying nitrogen at specific times in the growing season when plants need it most – but agribusinesses are unwilling to change their practices.

Study co-author, Prof. Peter Horton, weighs in on the dilemma:

“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... With over 100 million tonnes of fertiliser used globally each year to support agricultural production this is a massive problem, but environmental impact is not costed within the system and so there are currently no real incentives to reduce our reliance on fertiliser.”

Is organic the answer?

New Scientist doesn’t think so, arguing that organic farms use far more land per loaf than conventional farming and that this additional land could, in theory, be “set aside for wildlife or used for biomass energy.” Also, when farmers grow nitrogen-capturing legumes and spread them on fields as green fertilizer, the process still releases nitrous oxide.

It would have been interesting to see an analysis of waste added to the study since the UK wastes up to 24 million slices of bread per day. So maybe the solution is less complicated than it seems: We all need to start using up those stale crusts.