Agricultural producers face many pressures and challenges. With a growing population that will demand more food, and a strained climate that requires attention and adjustment of practices, it is difficult to know right from wrong and fact from fiction. 

“The pork industry has taken this topic by the horns,” said Dr. Frank Mitloehner, CLEAR Center Director. “They’ve been ahead of the curve on what needs to be done. Their focus on sustainability was not just on animal welfare or animal housing, but issues like environmental sustainability. They looked at sustainability and identified it as containing many things, which became the We Care Principles. This work was all done in the early 2000s, laying a strong foundation.”

The National Pork Board’s (NPB) We Care^® Ethical Principles offer a roadmap for the industry. These principles acknowledge pork producers’ responsibility to build and maintain the trust of customers through ethical practices and high-quality products. This includes safeguarding natural resources in all pork production practices.

Agriculture products, such as pork, provide affordable, nutrient-rich and sustainable food options for consumers. Pork is one of the most economical meat options and is one of the most consumed meat products on the market. Producers, researchers and industry professionals are working together to create efficiencies and minimize emissions to continue providing safe, healthy and responsibly produced food for generations to come. 

What are greenhouse gases?

To understand pork production’s impact on the environment begins with an understanding of greenhouse gases — the chemicals causing environmental warming and changes, according to the Unites States Environmental Protection Agency. 

Greenhouse gases trap heat in the atmosphere. The sun radiates solar beams to the surface of the earth. In an emissions-free world, these gases are reflected back into space. Greenhouse gases create a blanket that hovers in the atmosphere. The thicker this layer becomes, the more heat is retained in the atmosphere, contributing to climate change. The most well-known of these gases are carbon dioxide, methane and nitrous oxide. 

Methane is a greenhouse gas that is more than 28 times as potent and heat-wrapping than carbon dioxide per molecule. It is produced in agriculture from animal waste, fossil fuel production, biomass burning and natural sources such as wetlands. Methane is notably short-lived compared to carbon dioxide; methane stays in the atmosphere for about 10 years, compared to carbon dioxide’s 1,000. Mitloehner emphasizes that because of its lifespan, reducing methane emissions in livestock operations is paramount to reducing overall greenhouse gas emissions. 

“If we can reduce methane enough, we can reduce warming,” said Mitloehner. “This is why there is so much attention on animal agriculture, because it has an opportunity to be a climate solution. And while swine production is small part of livestock emissions, we’ve seen the sector strive to make improvements where possible.”

Total emissions from the agriculture sector 

According to the EPA, the agriculture sector — which includes crop and livestock production —accounts for 11% of the total direct greenhouse gas emissions. Agriculture soil management, cattle enteric emissions and manure management make up the industry’s footprint. Soil management accounts for just over half of the greenhouse gases in industry. 

Livestock emissions differ between ruminant and monogastric animals. Ruminants are animals with multiple-chambered stomachs, such as cattle, goats and sheep. Swine and poultry are monogastric animals and have one, simple stomach. The difference in these animals’ physiological makeups has varying effects on the industry’s footprint. As ruminants digest food, they are prone to enteric emissions, meaning they belch methane.

Mitloehner sees the swine industry as the envy of many around the world — swine are naturally less problematic than other livestock because they do not produce enteric emissions.

How are greenhouse gases emitted in pork production?  

Carbon dioxide, methane and nitrous oxide are all produced in the swine life cycle. Fossil fuels and livestock production emit carbon differently. Animals produce carbon through a biogenic carbon cycle. This means that atmospheric carbon dioxide, produced during photosynthesis, is taken out of the air and absorbed into plants and the soil. As animals eat and process plants in their feed or organically, they emit carbon back into the cycle through manure or belches. When there is a surplus of carbon in the cycle, it is emitted into the atmosphere instead of being pulled back into the cycle.

Alternatively, fossil fuels access carbon from animals and plants that have died, decayed and fossilized underground. Carbon is pulled from underground and burned for fuel. As carbon burns, it’s added directly into the atmosphere as carbon dioxide. 

Pigs consume and excrete compounds through manure. In pig feed, carbon is primarily found in carbohydrates, while nitrogen is found in proteins, often sourced from grains and other feed ingredients. When animals digest the feed, they convert these compounds to animal proteins digestible by humans.

Land application of manure helps continue the nitrogen cycle and the carbon cycle, both of which circulate elements in the natural forms they are found. 

Improved manure management cannot be undervalued 

As carbon in manure is broken down, it becomes methane. Manure that is uncovered, for example in lagoons or open pits, leeks methane into the atmosphere. Conversely, covered manure storage systems, such as anaerobic digesters, trap methane and process it into an energy source. 

Mitloehner says there are many valid ways to manage manure on swine farms, but believes in anaerobic digesters’ potential to reduce emissions through manure storage and processing.

“Anaerobic digesters are good options to manage manure because they optimize the production of methane,” Mitloehner said. “The methane doesn’t go into the air; it’s trapped and processed. It’s used to power vehicles or converted to power homes. If you want to reduce methane, you need to reduce volatile solids. Digesters are the best way to do that.”

Traditionally, manure is stored in open lagoons or uncovered pits. Capping manure in digesters traps the methane gas and converts it to a usable source of power. Because manure is a volatile solid, meaning it is converted to carbon dioxide and methane, separating and processing manure is crucial. Additionally, the organic materials that are left after digesting are land-applied as fertilizer with a much lower odor than untreated manure while emitting fewer greenhouse gases. 

Mitloehner brings attention to the “Pathways towards lower emissions report,” published in 2023, and centers the conversation on reducing emissions on the report’s researched predictions. The biggest opportunity to reduce the environmental impacts in pork production lies in improved manure management, although manure management is the least-effective total emission reduction strategy in livestock overall, according to the report. Notably, the report also highlights that decreasing the volume of meat consumed in human diets is one of the least effective in combatting greenhouse gas emissions. 

Looking to the future

Progress has been made across the industry’s environmental footprint. According to We Care’s 2021 Sustainability Report, producers have reduced their environmental impact in the past 50 years by using 75.9% less land, 25.1% less water and 7% less energy. Overall, the carbon emissions per pound of pork are 7.7% lower than they were 50 years ago. 

There is more work to be done, and scientists around the world are working and connecting tirelessly to address these issues. Mitloehner is confident the industry will continue to develop to address these issues to meet the challenge of creating more food while being stewards of the environment. 

“Over the last few decades, we’ve learned to breed more efficient animals that are directly related to the environmental footprint of livestock,” Mitloehner said. “We’ve seen great progress in breeding efficiencies in dairy cows to reduce methane, now we have to figure out breeding parameters for pigs. I believe research will lead to efficiencies to predict potential methane emission in pigs.” 

The CLEAR Center receives support from the Pork Checkoff, through the National Pork Board.