By Gabriella Sotelo for Sentient.
Broadcast version by Judith Ruiz-Branch for Illinois News Connection reporting for the Sentient-Public News Service Collaboration

Nitrous oxide (N₂O) emissions from agriculture are not only coming from soil. They’re also flowing through the streams that run alongside farms, a recent study finds. Researchers at the University of Minnesota and University of Illinois discovered more than one-third of regional nitrous oxide emissions were measured from streams.

While often overshadowed by the more widely known greenhouse gases like carbon dioxide and methane, nitrous oxide is the third-largest contributor to greenhouse gas emissions. Nitrous oxide also has an EPA-rated “Global Warming Potential” 273 times that of carbon dioxide (over a 100-year timescale), and is a significant contributor to ozone depletion. This means that even small amounts of nitrous oxide emissions can have a disproportionately large impact on global warming. And the flip side is also true: taking some action, including better manure management and eating less meat, can have a big climate impact for the better.

The discovery highlights a previously overlooked pathway for nitrous oxide to enter the atmosphere: as agricultural soils undergo the process of nitrification and produce nitrous oxide, the gas is transported via runoff into nearby streams. During the nitrification process, bacteria in soils break down ammonia — in this case from fertilizers — into nitrates that can produce nitrous oxide gas. While this gas may be released immediately from the soil, it can also become trapped in the soil or dissolve in water, only to be carried into streams during rainfall or snowmelt.

 “What we basically found is there [are] other pathways, and this stream emission could be important,” Zhongjie Yu, hydrologist and researcher in the study, tells Sentient.

Traditionally, when researchers consider nitrous oxide emissions from agriculture, they focus on soil. Excess nitrogen from fertilizers accumulates in agricultural soil, where it can be transformed into nitrous oxide, and released directly into the atmosphere. However, this new study suggests that emissions from streams — carrying runoff from agricultural fields — can be just as important, if not more so, in certain regions. Factory farms can be a major driver of this issue, as these operations produce large amounts of waste, composed partly of nitrogen.

When researchers consider initial nitrous oxide emissions, it’s often in the context of fertilizer input to soil. This excess nitrogen accumulates in agricultural soil, and can then lead to the direct release of nitrous oxide into the atmosphere.

Though the study used only the University of Minnesota’s Tall Tower Trace Gas Observator to sample air emissions, Yu and his research team are confident about the data.

“We found that N₂O is emitted from streams, but we believe it’s originally from fertilizer nitrogen. It is just carried by water, and gets emitted from those aquatic systems. It’s not saying it’s a natural source, but it’s still related to fertilizer nitrogen. But it just provides another pathway that N₂O gets lost from some land to the atmosphere.”

Yu also emphasized that agriculture is the dominant source of human-caused nitrous oxide emissions. This study not only challenges the conventional understanding of agricultural emissions, but also underscores a broader issue: agricultural runoff is not just a water quality problem — it is also a major contributor to climate change.

Nitrous Oxide: the Lesser Known Climate Threat

Human activities are significant contributors to nitrous oxide emissions. While other natural sources, such as the ocean, also release nitrous oxide, agricultural practices — particularly fertilizer application — are by far the largest contributor of anthropogenic emissions.

This gas is primarily produced when nitrogen-based fertilizers and manure are applied to agricultural soils. Microbes in the soil convert this nitrogen into nitrous oxide through processes such as nitrification and denitrification. The situation is made worse by the practices of industrial farming, which rely heavily on the use of synthetic fertilizers and animal waste.

Around 12 million tons of nitrogen are applied to crops each year in the United States. An EPA report found that agricultural soil management — like fertilizer use and other practices that boost nitrogen levels in the soil — accounts for nearly 75 percent of the United States’ nitrous oxide emissions. Within the agricultural sector itself, it makes up almost half of all emissions.

These soil management practices are primarily intended to optimize crop production, but much of the land is used for growing farm animal feed and biofuel crops. In 2020, only a small fraction of corn grown in the U.S. — less than two percent — was used for direct human food. Around 31 percent was dedicated to biofuels such as ethanol, while the majority, around 35 percent, went toward feeding livestock. With global meat consumption steadily rising, the demand for animal feed is expected to increase, further driving the need for feed crops like corn — along with higher fertilizer use and a corresponding rise in nitrous oxide emissions.

And now, the source of these emissions isn’t just the soil. Stream emissions can contribute to a much larger portion of annual nitrous oxide emissions than researchers previously thought.

“The high contribution of stream emissions suggests that soil emissions may have been overestimated in current regional nitrous oxide budgets,” Yu writes.

Yu points out that the link between agricultural runoff and stream emissions has often been overlooked in past research. Traditional methods use soil chambers to measure nitrous oxide emissions, a method that places a closed chamber over the soil, in order to capture any gases emitted from it. This approach primarily measures how much nitrous oxide is released directly from the soil, but misses the nitrogen that leaches out of the soil and flows into water systems, where it can then be converted into nitrous oxide and emitted to streams.

The Bottom Line

The source of nitrous oxide emissions from agriculture is more complex than scientists once thought. While traditional efforts to reduce nitrous oxide emissions have focused mainly on fertilizer management and improving soil efficiency, this new discovery emphasizes the importance of looking at the entire agricultural system, including runoff into streams. If the number of factory farms continue to rise, there is likely to be a rise in nitrous oxide pollution, particularly in streams, due to greater fertilizer use and runoff.

Yu mentions that improving water and nutrient management not only benefits water quality, but can also be a crucial tool in reducing greenhouse gas emissions. Fertilizer and manure runoff, especially from factory farms, can carry large quantities of nitrogen into waterways, which may then be converted into nitrous oxide — further complicating efforts to mitigate emissions from agriculture.

“We need to be a little bit careful here, because that water gets leached from surface soil and can end up in streams and rivers, carrying a lot of that greenhouse gas to those systems and having an impact there,” Yu says.


Gabriella Sotelo wrote this article for Sentient.


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Warmer winters and prolonged drought have turned Colorado forests into a budworm and beetle buffet, according to a new report from Colorado State University, and the thousands of acres of dead and dying trees left in their wake pose wildfire risks.

Dan West, entomologist for the Colorado State Forest Service, said four of the last five years have seen below-average precipitation, which is a problem because trees need water to produce resin, which they use to fight off insects.

"When we have significantly below or below-average precipitation, you couple that with warmer than average temperatures, it's really hard to be a tree in Colorado," West explained. "A lot of these bark beetles are just taking advantage of that."

Between 2023 and 2024, western spruce budworms increased their feasting grounds to 217,000 acres, up 15,000 acres from the previous year. The mountain pine beetle population continues to grow along the Front Range, in Gunnison County and in the southwest corner of the state. Bark beetles, the state's deadliest because they kill entire trees, have devoured 27,000 acres in places such as Rocky Mountain National Park and the San Juan and San Isabel national forests.

Warmer winters due to the burning of fossil fuels have taken away a key tree defense: deep freezes. West noted Colorado has not seen below-average winter temperatures in more than three decades.

"Maybe in my parents' generation or grandparents' generation, we used to calculate in overwinter mortality of bark beetles," West pointed out. "We pretty much don't do that anymore. The temperatures really never reach that overwintering cold temperature that can cause bark beetle mortality."

West added trees and insects naturally coexist in ecosystems and bark beetles act as sanitizers of the forest by recycling nutrients but with entire forests weakened, trees become low-hanging fruit.

"As these outbreaks continue over a number of years, we've got a lot of standing dead trees," West observed. "A cigarette, a campfire, a lightning strike -- whatever the spark may be -- that then has a lot of fuel to be able to burn through."

The Comanche 3 coal-fired power plant in Pueblo, Colo., is set to close in just six years -- and community leaders, regulators, and Xcel are considering plans to replace the unit's energy and economic contributions.

A new Energy Innovation report suggests that an industrial-scale energy park that harnesses wind, solar, and battery storage would check all the boxes.

Michelle Solomon, electricity policy manager with the nonpartisan think tank Energy Innovation, said the energy park would create some 300 permanent, high-paying jobs in plant operations, engineering, and more.

"The energy park could generate up to $40 million in annual tax revenue for Pueblo," said Solomon, "which is really important because they depend on this tax revenue that they're getting from Comanche right now -- for things like schools and libraries, things that the community can't afford to lose."

Comanche's connection to the power grid would allow the energy park to meet rising demand locally and in places like Colorado Springs and Denver.

A separate proposal calls for replacing Comanche with a small modular nuclear reactor, an energy source that does not emit carbon but remains controversial.

Tribal lands have been repeatedly targeted as radioactive waste dumps, and many still remember nuclear disasters at Three Mile Island, Chernobyl, and Fukushima.

Wind and solar are now the cheapest source for electricity - and Solomon said unlike nuclear-reactor or natural-gas plant projects, ratepayers would share startup costs with onsite manufacturers, who get guaranteed low-cost energy to produce fertilizer, hydrogen, and more.

"That could be used at any type of industry that's using heat," said Solomon. "So, that could be a steel plant, a cement plant, anything that's using heat for manufacturing."

Solomon said speed is also important for getting economic benefits flowing back into the community. The energy park could break ground before 2030, years earlier than other options.

"They are also the types of resources that can come online more quickly," said Solomon. "When the coal plant retires, the community can't wait a decade for a new resource to come online."

Trenton is set to become home to the region's largest battery storage facility but federal policy changes might change how it's funded.

The DTE Trenton Channel Energy Center would use clean energy tax credits from the Inflation Reduction Act but proposed federal cuts threaten the tax credits.

The plant is expected to store enough energy to power 40,000 homes for a day, create union jobs and help offset the area's economic loss from the 2022 closure of the Trenton Channel Power Plant.

James Harrison, director of renewable energies for the Utility Workers Union of America, said he has three generations of family history at the Trenton plant and is concerned about the potential effects of the proposed cuts.

"They're going to probably move forward with projects," Harrison explained. "The difference is going to be whether or not ratepayers are going to be on the hook to pay for that, or whether or not there's an opportunity to utilize tax credits to offset the cost to ratepayers."

In Michigan alone, more than 100 utility-scale projects are in development which could use the tax incentives. Those who want to eliminate the tax credits said the energy sector should compete without federal aid, arguing tax breaks add to the national debt and unfairly favor certain industries.

The Trenton facility is expected to start operations in mid-2026. The battery storage facility is also expected to generate more tax revenue than the former coal plant, which would benefit schools and public services in the Trenton/Wayne County area.

Harrison shared how his family history at the plant site colors his personal feelings about the new facility.

"I've been in the power industry almost 50 years," Harrison noted. "It's nice to see that the very first power plant that I worked at is being repurposed with modern technology to do the very same kind of job that original plant had provided to the community."

Some Republican lawmakers support keeping certain clean energy tax credits, citing their benefits for jobs and local economies. The Trenton project is also expected to contribute to Michigan's efforts to meet its renewable energy targets of using 60% clean energy by 2030, and 100% by 2040.


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