A Look at Nitrogen, Near and Far

By Willy Carleton

Driving along I-10, between Las Cruces and the Texas border, you might find yourself holding your breath as you press your foot a little more firmly on the accelerator. The stretch of highway known as Dairy Row, which I’ll return to later, has inspired a handful of online reviews that confirm that your eyes and nose are working just fine: “THE STENCH IS TERRIBLE,” “Looks very inhumane,” and “disgusting and sad,” read three separate reviews of one of the nine dairies along the row. It’s such a relief when you’re past that stretch of highway and your nostrils no longer burn that you might quickly banish the experience from your memory. But what exactly is in that foul smell, and where does it go? These questions, which even small children might pose to their unsure parents along the highway, lead to an even bigger one: What is the relationship between our food and the sky above us?

As the deep connection between food production and climate change has grown clearer in recent years, the conversation on climate and food has focused, for very good reason, on carbon and agriculture’s ability to capture it in the soil to help offset fossil fuel emissions and mitigate global warming. But recently, a growing number of scientists and policymakers have been making the case that nitrogen, which is essential to agricultural production, also plays a significant role in global warming and, unlike carbon dioxide, ozone depletion. As atmospheric carbon remains an imperative standard of measure for combating climate change, the upcoming decade, one group of scientists says, must also be the Nitrogen Decade.

The Nitrogen Decade follows on the heels of a century defined by this exceedingly common but often-overlooked element. At the turn of the twentieth century, as soils were being depleted globally from centuries of overuse, and as traditional nitrogen reserves such as guano were becoming scarcer, concern began to grow among Western scientists and policymakers that the world would not be able to feed itself. Thomas Malthus had published a seminal text on overpopulation a century earlier, and one of the most compelling reasons for late nineteenth-century scientists to take his thesis to heart was the argument that there would simply be too many mouths and too little nitrogen in the soils to feed them.

Then, almost miraculously it seemed, a German chemical-warfare engineer named Fritz Haber developed a solution that seemed too good to be true: a process to turn the abundant and inert nitrogen that is found in air into a form of nitrogen—ammonia—that could be used as fertilizer. With the help of Carl Bosch, Haber invented the Haber-Bosch process that produced the world’s first synthetic fertilizer and enabled tired soils to produce prodigious yields. Haber earned a Nobel Prize in 1918 for the invention, widely believed, both then and now, to have prevented wide-scale famine. In fact, over
40 percent of the world’s population today would not be alive if not for that invention. In other words, as Thomas Hager explains in The Alchemy of the Air, if every inch of arable soil were farmed with today’s best available agricultural methods, but without synthetic fertilizer, the world would only be able to provide about 4.5 billion people an adequate, vegetarian diet. The remaining 3.3 billion presumably would starve, and far more if current rates of meat consumption remained constant. Synthetic fertilizer seemed, at first at least, to be as close as we might hope to get to a free lunch.

It was also a Faustian bargain, and the true cost of the proverbial lunch is only growing. The root of the problem is that once inert (or nonreactive) nitrogen, which is the common form of nitrogen found in the air, is changed from its inert state to a reactive state, such as the ammonia in synthetic fertilizer and the ammonia formed by nitrogen-fixing bacteria in legumes, it can relatively easily continue to change states to become a lasting form of nitrogen pollution. (So, to answer the initial question in the intro: the foul stench of cows contains gases including ammonia, some of which eventually becomes nitrates and nitrous oxide.) Whereas nitrogen pollution from natural sources such as legumes or manure has always occurred to some extent with agriculture, the sheer scale of synthetic fertilizer created from previously unavailable nitrogen in the air has created unprecedented levels of nitrogen pollution. As a result, the past century has not only witnessed a twice-doubled population fueled largely by abundant and relatively cheap synthetic fertilizer—it has also quietly witnessed a host of growing nitrogen pollution problems, ranging from nitrate-induced oceanic dead zones to nitrate-contaminated drinking wells, including here in New Mexico, to the even less visible atmospheric warming and stratospheric ozone depletion caused by nitrous oxide.

Nitrous oxide, also known as laughing gas, is in reality a form of pollution worth taking very seriously. It is three hundred times more potent as a greenhouse gas than carbon dioxide and it also depletes stratospheric ozone, which all surface life depends on. It remains in the atmosphere for over one hundred years. Though we have made strides in curbing stratospheric ozone loss by banning chemicals such as CFCs and HFCs—a relatively rare and important example of how international agreements can successfully address environmental issues—nitrous oxide emissions could threaten this critical protection layer above us that humans and all other animals utterly depend on for immune system health and plant vitality. As Pieter Tans, a senior scientist at the NOAA Earth System Research Laboratory, put it to me: when it comes to stratospheric ozone depletion, “We are not out of the woods yet.”

Enter Dr. Mark Sutton, an environmental physicist and honorary professor at the University of Edinburgh, who is a lead advocate for the Nitrogen Decade and who has been working with the United Nations (UN) on a global framework to tackle nitrogen pollution. To meet the challenge of nitrogen pollution, in 2019, member states of the UN met in Colombo, Sri Lanka, and adopted the most ambitious global target to date for nitrogen pollution. Adoptees of the Colombo Declaration aim to halve global nitrogen waste by 2030, a target that Sutton has called “frighteningly ambitious.”

But such ambitious goals, he explained to me, are desperately needed. Sutton and I spoke via video, while he was in his office in Edinburgh. He began by repeating a common mantra among nitrogen scientists that nitrogen is “everywhere and invisible,” explaining that for this reason, its reach, ironically, can be easily overlooked. “If you’re going to try to fix the climate, and ignore nitrogen, you’re not going to meet your goals,” he continued. “We breathe in nitrogen seventy-eight percent of every breath we take. We completely ignore it because it doesn’t do much in the atmosphere, but equally if you start thinking about all those nitrogen pollution forms—air pollution, water pollution, nitrous oxide—because it’s all fragmented between different people’s issues, it all gets forgotten.”

Much of Sutton’s work aims to get the public to understand how nitrogen is a common thread in many of the planet’s most pressing environmental issues. “So nitrogen is quite complicated, and you could say, ‘Oh, don’t put it in front of the public, it’s too complicated to put it there.’ And I think that would be wrong. And part of the reason that’s wrong is that in a democracy, you only get action when the people are shouting about something. If there’s nobody shouting for it, it’s not in the public domain, it’s not in the international agreements, so you really struggle to make progress. My contention is that the public is not stupid, and the public actually loves complexity if they decide it’s going to be interesting to them.”

Throughout the conversation, he discussed three interconnected levels of approaches to curbing nitrogen pollution by increasing nitrogen-use efficiency. The first level is passing robust international agreements; the second comes through agricultural reform on farms; and the third comes through consumer action and choices, specifically through voting for climate-concerned officials and being aware of one’s nitrogen footprint and eating less meat and dairy as a result.

On the international level, Sutton explained that the UN has been increasing its work addressing nitrogen pollution, and global engagement, especially from the world’s four biggest nitrogen polluters—the United States, China, India, and Brazil—is critical. The goal of these international agreements, ultimately, is to halve global nitrogen pollution by 2030 by encouraging nitrogen-use efficiency. I asked him specifically what the role of the United States should be in this effort. “The US has a massive opportunity now to have the halve-nitrogen-waste discussion, because it’s an amazingly ambitious goal,” he explained. “If you said, ‘could the world as a whole halve nitrogen waste, while India, China, the US, and Brazil didn’t bother,’ it’s clear that the goal would not be met. Brazil has aligned already with the Colombo Declaration. Clearly, the US, China, and India have got to come too.”

International agreements, Sutton made clear, are critical. Atmospheric pollutants cross borders and require cooperation at the highest levels to control. But the sources of these pollutants are local in nature too. Agriculture is by far the largest contributor of nitrogen pollution, so changing agricultural practices at all scales is an extremely important part of the conversation. Because livestock often feed on agricultural products grown with synthetic fertilizer, such as corn, and because their manure is also a source of various forms of nitrogen pollution, halving meat and dairy consumption in the global diet would significantly reduce nitrogen pollution. While not all meat and dairy carry the same nitrogen footprint, and sourcing meat from local ranchers and farmers who practice regenerative agriculture can help reduce the carbon and nitrogen footprints of the products, there is room for improvement in all agricultural systems, and reducing meat intake across the board will reduce nitrogen pollution.

“When you engage with farmers, they will often say, ‘Oh leave me alone, I have too many pressures, it would cost me to take action.’ But if you add up the value of all the air/land/water losses as a wasted form of nitrogen, you get this two hundred billion dollars a year. So halve nitrogen waste, save a hundred billion. It’s clear that there is actually an opportunity for profit in it if you’re smart, so it’s about learning to be smart and mobilizing the circular economy.”

I asked Sutton about the role of regenerative agriculture. While industrial farming is by far a larger contributor of nitrogen pollution, and thus a far more pressing concern in terms of nitrogen, he was quick to note that it is not only large-scale farmers and ranchers that need to pay attention to nitrogen pollution. “Whether you are an intensive-style farmer or a regenerative or organic farmer, there is something that you can do better in the system that you’ve got,” he began. The ways small-scale farmers and ranchers can improve are often highly technical, but the bottom line for Sutton is that tracking and managing any form of reactive nitrogen—whether it’s ammonia from synthetic fertilizer or from leguminous cover crops and in animal manure—will improve all types of farming systems. “One thing regenerative farmers will often tell you is that they don’t make pollution because they don’t have fertilizers, which is incorrect because if you, let’s say, make a green cover crop with legumes, and you want to have it as part of a good rotation to build the carbon and nitrogen in your soil, the moment you take a legume that has fixed the nitrogen out of the atmosphere with its roots and plow it into the soil, suddenly you’re going to get a big pulse of mineralization and you risk nitrous oxide emissions and nitrate leaching.” In other words, while regenerative farming represents a positive and important step away from widespread overuse of synthetic fertilizers, even many farmers practicing forms of regenerative agriculture can often improve their yields and further reduce their nitrogen footprint by paying close attention to how nitrogen enters and leaves their fields.   

Agriculture is driven in part by consumer choices, and so consumers play a large role, as well. For Sutton, this starts with education about nitrogen pollution in all its forms:

“Seventy percent of your nitrogen footprint is probably due to the food system and your food choices. The other thirty percent is due to transport and energy. For ordinary citizens, the food system is the number-one thing in their personal nitrogen footprint. We’ve met peak engagement on nitrogen and food in Europe now, because they’ve got used to the conversation, whereas my guess is you’re still  at the edge in the US with this extremely sensitive discussion, liable for polarization. But that is a massive opportunity for getting the message out. . . . The very sensitivity of the topic in the US means it’s still got plenty of media mileage.”

Reflecting on these issues, I turned my eye back toward what is likely one of the biggest sources of nitrogen pollution in the state: dairies. New Mexico is home to more than 130 dairies that ship their products out of state; in 2018, they produced more than eight billion pounds of milk. For nearly two decades, New Mexico dairies have had the largest average herd size in the country; a recent agricultural census tallied the average to be 3,187 cows per dairy. Most of these dairies are in the southern and eastern parts of the state, and perhaps the epicenter is along that short stretch of I-10 known as Dairy Row.

New Mexico’s dairies have long been a source of jobs and a known source of nitrate-caused water pollution—and hence conflict. For many who live near the dairies, well water cannot be used safely for drinking or bathing, and groups such as the New Mexico Citizens Dairy Coalition (NMCDC) have challenged the dairies to provide more oversight, monitoring, and remediation of groundwater pollution. It is a critical public health issue for those living nearby.

Given the immediate dangers of contaminated drinking water, it is little wonder that other forms of nitrogen pollution, both here in New Mexico and throughout the world, receive less attention in the localities hit hardest by nitrates.

Despite the lack of attention, New Mexico’s dairies are very likely contributing to atmospheric pollution. Manure management alone led to 5 percent of total nitrous oxide emissions in the United States in 2017. Large dairies also contribute to nitrous oxide emissions through their reliance on industrial corn to feed cows; fertilizer use and soil management accounts for 74 percent of total nitrous oxide emissions in the country. As Dan Lorimier of the NMCDC told me, “There is no sense of what the [local] dairy industry’s contribution to air pollution is here because we don’t monitor that at all.” But Lorimier has little doubt that the dairies, combined with methane flaring in our state’s oil fields, have contributed to global atmospheric pollution. How much is an open question. “I think that would be a great direction, to try to get public awareness of the dairy industry’s contributions to greenhouse and other air pollutants on the menu of things to be looking at.”

New Mexico’s dairies are just one of many ways that local agriculture affects our atmosphere. Farmers and ranchers of all scales can better incorporate nitrogen efficiency into their systems, reducing the nitrogen footprint of the food we rely on. Using tools such as N-Calculator at n-print.org, institutions and individual consumers can learn about and prioritize their footprint more.

But there are limits to local solutions. This is not a problem that can be solved simply by buying food from co-ops and farmers markets; it is also a global problem that requires engaging in global conversations and working toward international-level solutions. So while eating less meat, supporting regenerative ranching for the meat we do purchase, and prioritizing food with lower nitrogen footprints all play an important part of grappling with this issue, so too will more-than-local actions like urging elected officials to join critical international pacts to curb nitrogen waste. When it comes to stratospheric food problems, solutions must come in all links of the food chain. 

Editor at Edible New Mexico and The Bite | + other stories

Willy Carleton is a co-editor of edible New Mexico and The Bite. He is the author of Fruit, Fiber, and Fire: A History of Modern Agriculture in New Mexico, which explores the cultural and environmental history of apples, cotton, and chiles in our region.