Food production generates more than a third of manmade greenhouse gas emissions – a new framework tells us how much comes from crops, countries and regions

A farmer walks through a rice paddy in India’s northeastern state of Assam. Buu Boro /AFP via Getty Images

by Xiaoming Xu and Atul Jain (University of Illinois at Urbana-Champaign)

Producing enough food for a growing world population is an urgent global challenge. And it’s complicated by the fact that climate change is warming the Earth and making farming harder in many places.

Food production is a big contributor to climate change, so it’s critically important to be able to measure greenhouse gas emissions from the food sector accurately. In a new study, we show that the food system generates about 35% of total global man-made greenhouse gas emissions.

Breaking down this share, production of animal-based foods – meat, poultry and dairy products, including growing crops to feed livestock and pastures for grazing – contributes 57% of emissions linked to the food system. Raising plant-based foods for human consumption contributes 29%. The other 14% of agricultural emissions come from products not used as food or feed, such as cotton and rubber.

We are atmospheric scientists who study the effects of agriculture and other human activities on Earth’s climate. It’s well known that producing animal-based foods generates more greenhouse gas emissions than plant-based foods, which is why shifting toward a more plant-based diet is recognized as an option for curbing greenhouse gas emissions and climate change.

But to quantify the potential impact of such a shift, we saw a need for better tools to estimate emissions from individual plant- and animal-based food items, with more details about how emissions are calculated and covering all food-related sub-sectors, such as land use change and actions beyond the farm gate.

Current methods rely on sparse data and simplified representations of many key factors, such as emissions from farmland management. They don’t treat different sub-sectors consistently or calculate emissions for producing many specific commodities.

To fill those gaps, we have developed a comprehensive framework that combines modeling and various databases. It enables us to estimate average yearly global emissions of the greenhouse gases carbon dioxide, methane and nitrous oxide from the production and consumption of plant- and animal-based human food. Currently, our study covers the years 2007-2013. Here are some of the insights it offers, using data that represents an average of those years.

Hunger and food insecurity are urgent global challenges. Climate change is one contributing factor.

Greenhouse gases from food production

We considered four major sub-sectors of emissions from plant- and animal-based food production. Overall, we calculated that the food system produces emissions that are equivalent to approximately 17.3 billion metric tons (17.318 teragrams) of carbon dioxide yearly.

Land use change – clearing forests for farms and ranches, which reduces carbon storage in trees and soils – accounts for 29% of total food production greenhouse gas emissions. Another 38% comes from farmland management activities, such as plowing fields, which reduces soil carbon storage, and treating crops with nitrogen fertilizer. Farmers also burn a lot of fossil fuel to run their tractors and harvesters.

Raising livestock generates 21% of greenhouse gas emissions from food production. It includes methane belched by grazing animals, as well as methane and nitrous oxide released from livestock manure. The remaining 11% comes from activities that occur beyond farm gates, such as mining, manufacturing and transporting fertilizers and pesticides, as well as energy use in food processing.

Graphic of agricultural greenhouse gas sources and sinks.
Many agricultural activities release carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) to the atmosphere. Some store carbon in plants and soil. CRS

Which foods generate the most greenhouse gas emissions?

Our framework makes it possible to compare how different food products and food-producing regions affect Earth’s climate.

Among animal-based foods, beef is the largest contributor to climate change. It generates 25% of total food emissions, followed by cow milk (8%) and pork (7%).

Rice is the largest contributor among plant-based foods, producing 12% of the total greenhouse gas emissions from the food sector, followed by wheat (5%) and sugarcane (2%). Rice stands out because it can grow in water, so many farmers flood their fields to kill weeds, creating ideal conditions for certain bacteria that emit methane.

This helps to explain why South and Southeast Asia have the greatest food-production-related emissions by region, producing 23% of the global total. This region is the only place where plant-based emissions are larger than animal-based emissions. South America is the second-largest emitter at 20%, and has the largest emissions from animal-based food, reflecting the dominance of ranching there.

Among individual countries, China, India and Indonesia have the highest emissions from plant-based food production, contributing 7%, 4%, and 2% respectively of global food-related greenhouse gas emissions. The countries with leading emissions from the production of animal-based foods are China (8%), Brazil (6%), the U.S. (5%) and India (4%).

A tractor spreads manure on a dirt field.
Injecting manure into a field as fertilizer in Lawler, Iowa. Manure management is a major source of greenhouse gas emissions from livestock. AP Photo/Charlie Neibergall

How food production affects land use

Our framework also shows that raising animal-based foods consumes six times as much land as producing plant-based foods.

Worldwide, we estimate that humans are using 18 million square miles (4.6 billion hectares) of land to produce food – about 31% of Earth’s total land area, excluding areas covered by snow and ice. Of this, 30% is cropland and 70% is various types of grazing land.

Looking at how these areas are managed, we estimate that 13% of total agricultural land is being used to produce plant-based foods. The other 77% is being used to produce animal-based foods, including croplands that are growing animal feed and grazing lands. The remaining 10% is being used to raise other products, such as cotton, rubber and tobacco.

Our study uses a consistent framework to provide a complete estimation of greenhouse gas emissions from food production and consumption, covering all food-related sub-sectors, at local, country, regional and global scales. It can help policymakers identify the plant- and animal-based food commodities that contribute the largest shares to climate change, and the higest-emitting sub-sectors at different locations.

Based on these results, governments, researchers and individuals can take actions to reduce emissions from high-emitting food commodities in different places. As U.N. leaders have stated, making food production more climate-friendly is essential to reduce hunger in a warming world.

Xiaoming Xu, Postdoctoral Research Associate in Atmospheric Sciences, University of Illinois at Urbana-Champaign and Atul Jain, Professor of Atmospheric Sciences, University of Illinois at Urbana-Champaign

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Sustainable Refrigeration Summit

Sep 27-Oct 8. 2021 (free, online)
More information and to register

The zero emissions movement is expanding rapidly at the local, state, and federal levels, expanding regulatory pressures on food retailers to address refrigerant emissions. This free virtual summit will bring together key stakeholders – including food retailers, manufacturers, service contractors, engineers, government agencies, policymakers, utilities, energy, and environmental stakeholders – to advance the solutions needed to achieve a zero emissions future for supermarket refrigeration.

Hear the latest regulatory and industry trends and learn from the food retailers, industry experts, and policymakers shaping the future of sustainable refrigeration.

Hosted over a 2-week period, the summit will feature on-demand Technology Sessions and 1-2 daily live sessions. See the schedule here.

EPA announces plans to undertake three new rulemakings on PFAS contamination

Read the full post from the National Association of Counties.

On September 8, the EPA released the Preliminary Effluent Guidelines Program Plan 15 (Preliminary Plan 15), which announces the agency’s initiation of three new rulemaking processes to reduce contaminants such as PFAS. Preliminary Plan 15 identifies existing and new industries to undergo regulatory action and provides a rulemaking schedule for such activities. Additionally, EPA will conduct studies on PFAS in wastewater discharges from landfills and other sources.

Chicago passes watered-down plastic foodware ‘ban’ that critics call greenwashing

Read the full story from WTTW.

Under a new law passed Tuesday by a 37-10 vote from the Chicago City Council, restaurants will only be allowed to provide single-use “foodware” — a broad category that includes everything from plastic utensils to ketchup packets — if the items are requested by customers with takeout and delivery orders.

Banks at bigger risk from climate than subprime mortgages, researcher says

Read the full story in The Hill.

Climate change is posing a bigger risk to bank balance sheets than the subprime mortgage crisis that contributed to the Great Recession, according to the co-author of a new study on the vulnerability of commercial loans.

The study, conducted by the sustainability nonprofit Ceres and released last week, found that up to 10 percent of the value of U.S. commercial loans at leading banks is at risk of being wiped out by the effects of floods, fires, extreme heat and hurricanes.

From ocean to table: Sardines tainted with microplastics

Read the full story from Cal State Fullerton.

In a basement laboratory, Cal State Fullerton biology graduate student Chelsea Bowers dissects Pacific sardines and blends them into a creamy “shake.”

It won’t go well with a burger and fries, but her hope is that the concoction of sardine stomach and muscle tissues will help find solutions to microplastic contamination of ocean life.

Cold chain warms to sustainable goals

Read the full story in Food Manufacture.

Temperature-controlled storage and distribution has come under considerable scrutiny, as the food industry balances a need to keep food fresh and safe with the environmental and financial cost of doing so.

Can artificially altered clouds save the Great Barrier Reef?

Read the full story in Nature.

Australian scientists are rushing to develop new technologies — such as ways to block sunlight — to help preserve corals in the face of climate change.

Hazardous chemicals, data science challenges on tap at DNTP meeting

Read the full story at Environmental Factor.

The substitution of hazardous chemicals with equally hazardous ones and the daunting accumulation of toxicological data were among the challenges covered at the Aug. 4 meeting of the National Toxicology Program Board of Scientific Counselors, held virtually.

Hurricane Ida turned into a monster thanks to a giant warm patch in the Gulf of Mexico – here’s what happened

A computer animation reflects the temperature change as eddies spin off from the Loop Current and Gulf Stream along the U.S. Coast.

by Nick Shay, (University of Miami)

As Hurricane Ida headed into the Gulf of Mexico, a team of scientists was closely watching a giant, slowly swirling pool of warm water directly ahead in its path.

That warm pool, an eddy, was a warning sign. It was around 125 miles (200 kilometers) across. And it was about to give Ida the power boost that in the span of less than 24 hours would turn it from a weak hurricane into the dangerous Category 4 storm that slammed into Louisiana just outside New Orleans on Aug. 29, 2021.

Nick Shay, an oceanographer at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, was one of those scientists. He explains how these eddies, part of what’s known as the Loop Current, help storms rapidly intensify into monster hurricanes.

How do these eddies form?

The Loop Current is a key component of a large gyre, or circular current, rotating clockwise in the North Atlantic Ocean. Its strength is related to the flow of warm water from the tropics and Caribbean Sea into the Gulf of Mexico and out again through the Florida Straits, between Florida and Cuba. From there, it forms the core of the Gulf Stream, which flows northward along the Eastern Seaboard.

In the Gulf, this current can start to shed large warm eddies when it gets north of about the latitude of Fort Myers, Florida. At any given time, there can be as many as three warm eddies in the Gulf, slowly moving westward. When these eddies form during hurricane season, their heat can spell disaster for coastal communities around the Gulf.

A computer model shows the current and eddies.
The Loop Current runs from the tropics through the Caribbean and into the Gulf of Mexico, then joins the Gulf Stream moving up the East Coast. NASA/Goddard Space Flight Center Scientific Visualization Studio

Subtropical water has a different temperature and salinity than Gulf common water, so its eddies are easy to identify. They have warm water at the surface and temperatures of 78 degrees Fahrenheit (26 C) or more in water layers extending about 400 or 500 feet deep (about 120 to 150 meters). Since the strong salinity difference inhibits mixing and cooling of these layers, the warm eddies retain a considerable amount of heat.

When heat at the ocean surface is over about 78 F (26 C), hurricanes can form and intensify. The eddy that Ida passed over had surface temperatures over 86 F (30 C).

How did you know this eddy was going to be a problem?

We monitor ocean heat content from space each day and keep an eye on the ocean dynamics, especially during the summer months. Keep in mind that warm eddies in the wintertime can also energize atmospheric frontal systems, such as the “storm of the century” that caused snowstorms across the Deep South in 1993.

To gauge the risk this heat pool posed for Hurricane Ida, we flew aircraft over the eddy and dropped measuring devices, including what are known as expendables. An expendable parachutes down to the surface and releases a probe that descends about 1,300 to 5,000 feet (400 to 1,500 meters) below the surface. It then sends back data about the temperature and salinity.

This eddy had heat down to about 480 feet (around 150 meters) below the surface. Even if the storm’s wind caused some mixing with cooler water at the surface, that deeper water wasn’t going to mix all the way down. The eddy was going to stay warm and continue to provide heat and moisture.

That meant Ida was about to get an enormous supply of fuel.

Map of surface temperatures.
Ida’s route to Louisiana passed through very warm water. The scale, in meters, shows the maximum depth at which temperatures were 78 degrees Fahrenheit (26 C) or greater. University of Miami, CC BY-ND

When warm water extends deep like that, we start to see the atmospheric pressure drop. The moisture transfers, or latent heat, from the ocean to atmosphere are sustained over the warm eddies since the eddies are not significantly cooling. As this release of latent heat continues, the central pressures continue to decrease. Eventually the surface winds will feel the larger horizontal pressure changes across the storm and begin to speed up.

That’s what we saw the day before Hurricane Ida made landfall. The storm was beginning to sense that really warm water in the eddy. As the pressure keeps going down, storms get stronger and more well defined.

When I went to bed at midnight that night, the wind speeds were about 105 miles per hour. When I woke up a few hours later and checked the National Hurricane Center’s update, it was 145 miles per hour, and Ida had become a major hurricane.

How hurricanes draw fuel from water water. Credit: NOAA

Is rapid intensification a new development?

We’ve known about this effect on hurricanes for years, but it’s taken quite a while for meteorologists to pay more attention to the upper ocean heat content and its impact on the rapid intensification of hurricanes.

In 1995, Hurricane Opal was a minimal tropical storm meandering in the Gulf. Unknown to forecasters at the time, a big warm eddy was in the center of the Gulf, moving about as fast as Miami traffic in rush hour, with warm water down to about 150 meters. All the meteorologists saw in the satellite data was the surface temperature, so when Opal rapidly intensified on its way to eventually hitting the Florida Panhandle, it caught a lot of people by surprise.

Today, meteorologists keep a closer eye on where the pools of heat are. Not every storm has all the right conditions. Too much wind shear can tear apart a storm, but when the atmospheric conditions and ocean temperatures are extremely favorable, you can get this big change.

Hurricanes Katrina and Rita, both in 2005, had pretty much the same signature as Ida. They went over a warm eddy that was just getting ready to be shed form the Loop Current.

Hurricane Michael in 2018 didn’t go over an eddy, but it went over the eddy’s filament – like a tail – as it was separating from the Loop Current. Each of these storms intensified quickly before hitting land.

Of course, these warm eddies are most common right during hurricane season. You’ll occasionally see this happen along the Atlantic Coast, too, but the Gulf of Mexico and the Northwest Caribbean are more contained, so when a storm intensifies there, someone is going to get hit. When it intensifies close to the coast, like Ida did, it can be disastrous for coastal inhabitants.

A man walks through the debris of an office with the roof torn off.
Hurricane Ida hit the coast with 150 mph winds that tore roofs off homes and buildings. Its storm surge caused widespread flooding outside the region’s levee system. AP Photo/David J. Phillip

What does climate change have to do with it?

We know global warming is occurring, and we know that surface temperatures are warming in the Gulf of Mexico and elsewhere. When it comes to rapid intensification, however, my view is that a lot of these thermodynamics are local. How great a role global warming plays remains unclear.

This is an area of fertile research. We have been monitoring the Gulf’s ocean heat content for more than two decades. By comparing the temperature measurements we took during Ida and other hurricanes with satellite and other atmospheric data, scientists can better understand the role the oceans play in the rapid intensification of storms.

Once we have these profiles, scientists can fine-tune the computer model simulations used in forecasts to provide more detailed and accurate warnings in the futures.

Nick Shay, Professor of Oceanography, University of Miami

This article is republished from The Conversation under a Creative Commons license. Read the original article.