Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Scientists Uncover the True Cost of a Loaf of Bread

Scientists Uncover the True Cost of a Loaf of Bread

By Lucy Goodchild van Hilten

Bread has recently been labeled a bad guy, with millions of people opting to ditch the dough and eat a gluten-free diet to stay trim and healthy. But it turns out there's another reason to steer clear of bread: it's having a massive impact on the environment.

Scientists in the UK have worked out the greenhouse gas emissions produced by making a standard loaf of bread, pinpointing the emissions hotspots in the process. With GHG emissions equivalent to about half a kilo (1.3 pounds) of carbon dioxide per loaf, bread accounts for half a percent of the UK's total emissions. That may not seem like a lot, but considering that the nation's entire agriculture industry accounts for 10 percent of total emissions, it's clear that bread, as a single food product, has a pretty huge impact.

The good news is there's now a clear target to reduce the impact: Nearly half of the emissions (0.589kg, or 13.7oz) come from fertilizer used to grow the wheat. Writing in Nature Plants, Peter Horton and his colleagues from the University of Sheffield analyzed the whole manufacturing process, from planting the seed to putting the bread on the shelf. They found the bulk of the greenhouse gases come from the farm.

"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," commented Horton, who is chief research advisor to the University of Sheffield's Grantham Center for Sustainable Futures.

Bread: the bad guy?

Despite getting bad press for its gluten content (which scientists now say we actually need), bread is still one of the most widely eaten foods; the average American eats bread 77 times a year and almost 160 million Americans eat one loaf a week (and more than 11 million eat more than five loaves).

Bread has four main ingredients: flour, yeast, salt and water. The wheat is first grown and harvested, then the grains milled to make the flour—all this before the ingredient is processed, packaged and ready to bake. A standard loaf of bread contains about 16 ounces of flour, and this is what has the biggest impact on the environment, according to the new research.

The researchers looked at every aspect of bread manufacturing, analyzing the whole life cycle of a loaf, from growing the wheat to packaging the bread and transporting it to the shop. They found that nearly 66 percent of the emissions came from growing the wheat: tilling the soil, harvesting and irrigation all require emissions-producing machinery. But a whopping 43 percent of the greenhouse gases produced came from using fertilizer to grow the crops.

"We found in every loaf there is embodied global warming resulting from the fertilizer applied to farmers' fields to increase their wheat harvest," said Liam Goucher, the study's lead author.

A system reliant on fertilizer

For the calculations in their new study, the team focused on one particular farm in Lincoln in the UK, but the significant emissions from the fertilizer are not unique to that farm—or the crop. In fact, food is responsible for about one-third of all our greenhouse gas emissions, and a lot of this is down to fertilizer use. An estimated 60 percent of agricultural crops depend on fertilizer; wheat farmers use ammonium nitrate fertilizer to grow their crops. It boosts growth by providing nitrogen, but it also contains and releases a multitude of substances with a potential impact on climate, including ammonia, carbon dioxide and methane.

"If you want to reduce the climate impact of food production, we need to think of fertilizer manufacturing and fertilizer application as one place where we have big leverage to reduce climate impact," said Navin Ramankutty of the University of British Columbia, Vancouver, who was not involved in the study.

The emissions related to fertilizer use stretch back into its own production—a lot of energy is needed to make the fertilizer in the first place. Then when it's used and breaks down in the soil, it releases nitrous oxide. This gas accounts for nearly two-thirds of agricultural emissions—as a food-related greenhouse gas, it's second only to carbon dioxide. What's more, it has 298 times the global warming potential of carbon dioxide, making fertilizer a serious problem for climate change.

"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," said Horton. "With over 100 million tons of fertilizer 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 fertilizer."

Taking responsibility as a team

So we've got a problem in the system, but who's going to fix it? According to the researchers, it's something that needs to be addressed by everyone involved, from the farmer who plants the seeds to the consumer who takes a bite out of a sandwich.

We know plenty of ways to reduce the impact of using fertilizer, such as using it at key points during the season rather than continuously, and using different cropping systems—by planting vegetables between crop cycles (decreasing "fallow frequency"), farmers can keep the land in use and improve the ability of the soil to hold carbon.

The biggest challenge will be implementing these changes in places where farmers rely on fertilizer to protect their income; after all, it's a surefire way to make sure the crop grows, regardless of the impact it has on the environment.

Yet the responsibility doesn't end with the farmer, said Lenny Koh, who came up with the method for analyzing bread in the new study: "The findings raise a very important issue—whose responsibility is it to bring about the implementation of these interventions: the fertilizer manufacturer, the farmer, the retailer or the consumer?

"There is a growing recognition for a range of industrial processes of the notion of extended producer responsibility—the producer being responsible for downstream impact, expanded to the idea of shared producer and consumer responsibility. The consumer is key, whether being persuaded to pay more for a greener product or by applying pressure for a change in practice."

The obvious choice we can make is organic—given the proportion of emissions that come from fertilizer, making sure the bread we're eating is organic can make an immediate and significant difference. Less obvious is where we eat: researchers in China found that dining out has nearly double the carbon emissions of eating at home.

While the jury may still be out on whether bread is the bad guy for our health, it's clear that the slice of toast we eat in the morning or that lunchtime sub has just as much of an effect on the environment as it does on our waistlines. The agricultural industry has plenty of work to do to reduce the impact of the wheat that ends up in our sandwiches. But in the meantime, when it comes to cutting the carbon from our food, the decisions we make as consumers can help, too.

Reposted with permission from our media associate AlterNet.

EcoWatch Daily Newsletter

A large patch of leaked oil and the vessel MV Wakashio near Blue Bay Marine Park off the coast of southeast Mauritius on Aug. 6, 2020. AFP via Getty Images

The environmental disaster that Mauritius is facing is starting to appear as its pristine waters turn black, its fish wash up dead, and its sea birds are unable to take flight, as they are limp under the weight of the fuel covering them. For all the damage to the centuries-old coral that surrounds the tiny island nation in the Indian Ocean, scientists are realizing that the damage could have been much worse and there are broad lessons for the shipping industry, according to Al Jazeera.

Read More Show Less
A quality engineer examines new solar panels in a factory. alvarez / Getty Images

Transitioning to renewable energy can help reduce global warming, and Jennie Stephens of Northeastern University says it can also drive social change.

For example, she says that locally owned businesses can lead the local clean energy economy and create new jobs in underserved communities.

"We really need to think about … connecting climate and energy with other issues that people wake up every day really worried about," she says, "whether it be jobs, housing, transportation, health and well-being."

To maximize that potential, she says the energy sector must have more women and people of color in positions of influence. Research shows that leadership in the solar industry, for example, is currently dominated by white men.

"I think that a more inclusive, diverse leadership is essential to be able to effectively make these connections," Stephens says. "Diversity is not just about who people are and their identity, but the ideas and the priorities and the approaches and the lens that they bring to the world."

So she says by elevating diverse voices, organizations can better connect the climate benefits of clean energy with social and economic transformation.

Reposted with permission from Yale Climate Connections.

The frozen meat section at a supermarket in Hong Kong, China, in February. Chukrut Budrul / SOPA Images / LightRocket via Getty Images

Imported frozen food in three Chinese cities has tested positive for the new coronavirus, but public health experts say you still shouldn't worry too much about catching the virus from food or packaging.

Read More Show Less
This image of the Santa Monica Mountains in California shows how a north-facing slope (left) can be covered in white-blooming hoaryleaf ceanothus (Ceanothus crassifolius), while the south-facing slope (right) is much less sparsely covered in a completely different plant. Noah Elhardt / Wikimedia Commons / CC by 2.5

By Mark Mancini

If weather is your mood, climate is your personality. That's an analogy some scientists use to help explain the difference between two words people often get mixed up.

Read More Show Less
Flames from the Lake Fire burn on a hillside near a fire truck and other vehicles on Aug. 12, 2020 in Lake Hughes, California. Mario Tama / Getty Images

An "explosive" wildfire ignited in Los Angeles county Wednesday, growing to 10,000 acres in a little less than three hours.

Read More Show Less
Although heat waves rarely get the attention that hurricanes do, they kill far more people per year in the U.S. and abroad. greenaperture / Getty Images

By Jeff Berardelli

Note: This story was originally published on August 6, 2020

If asked to recall a hurricane, odds are you'd immediately invoke memorable names like Sandy, Katrina or Harvey. You'd probably even remember something specific about the impact of the storm. But if asked to recall a heat wave, a vague recollection that it was hot during your last summer vacation may be about as specific as you can get.

Read More Show Less


A film by Felix Nuhr.

Thailand has a total population of 5,000 elephants. But of that number, 3,000 live in captivity, carrying tourists on their backs and offering photo opportunities made for social media.

Read More Show Less