The underrated enemy of the climate crisis

Whenever we talk about dangerous greenhouse gases, our minds almost automatically go to carbon dioxide and methane. However, there is one more type of pollution that is arguably one of the most intractable environmental problems of our time: nitrogen pollution.

Human activity affects the nitrogen (N) cycle more severely than the carbon (C) cycle. In fact, the N cycle is perhaps the most affected of all the world’s major biogeochemical cycles, with serious implications for human health, biodiversity, and air and water quality.

Ammonia and nitrogen oxides, which play a significant role in climate change, contribute to the creation of particulates and acid rain that cause respiratory problems and cancer in humans, as well as widespread damage to forests and buildings. In particular, nitrous oxide is a particularly potent greenhouse gas, exhibiting approximately 300 times more heat-trapping capacity in the atmosphere than carbon dioxide.

The climate crisis amplifies the adverse effects of N, but also vice versa. According to a study in the journal Science, the climate crisis is expected to increase the amount of nitrogen ending up in US rivers and other waterways by 19% on average by the end of the century, and more in more affected. , especially in the Mississippi River (24% increase) and Northeast (28% increase), not including potential increases in nitrogen inputs from agricultural intensification or human population growth.

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Unfortunately, a painful realization of our time is that the means we rely on to make our lives more comfortable can also kill us. We depend on nitrogen and the fertilizers that feed us, and now it seems that the combination of climate change and nitrogen pollution is multiplying the chances that we will see serious disasters in the world around us in the coming years.

But somehow we need to grow more food to feed the world’s growing population while minimizing the problems associated with the use of nitrogen fertilizers.

The necessary ingredient

Nitrogen is an essential building block for amino acids, proteins, and cellular DNA. It is an element of great importance for life and the environment, and plants have a fundamental dependence on it, since it is the nutrient they need in the greatest quantity to carry out their biological processes. Animals and humans take the necessary nitrogen from food of plant and animal origin.

Nitrogen gas (N₂) makes up 78% of the air we breathe, but cannot be used directly by plants. “Nitrogen is taken up by plants in the desired form through fertilizers made by mixing atmospheric nitrogen with gaseous hydrogen under enormous pressure (200 times atmospheric pressure). This is the pressure we would feel if we were submerged to 2,000 meters (2,000 meters).∼6,500 feet) under the sea, a distance greater than 6 Eiffel Towers stacked on top of each other! It is estimated that more than 150 million tons of synthetic fertilizers are added to the soil worldwide each year to control nitrogen deficiency that affects plant growth and vigor. And to think that in 1961 the use of nitrogenous fertilizers was limited to 11 million tons worldwide! describes the Assistant Professor of Environmental Microbiology at the University of Thessaly, Ms. Evangelia Papadopoulou.

In fact, nitrogen from fertilizers now accounts for more than half of the protein in the human diet. However, about 50% of the nitrogen applied to fields is lost to the environment by volatilization in the form of ammonia (3-21%) or by leaching into groundwater (nitrification) in the form of nitrate ions (13% ), either ending up in the atmosphere as nitrous oxide (12%).

With increasing use of nitrogenous fertilizers over time, these losses also increase. Nitrogen loss causes damage on a large scale and will cause even more damage if its losses are not controlled. Lost nitrogen also hurts farmers, which can reduce crop yields or lead to wasted fertilizer. The damage is most severe for small farmers in developing countries, where nitrogen fertilizers often absorb the highest costs of agriculture. Reduced production from nitrogen loss can account for up to 25% of household income.

With a growing population and a changing climate, we need more than ever to optimize nitrogen use and minimize losses. The solution to the nitrogen challenge will have to come from a combination of technological innovation, policy and consumer action, scientists say.

back to the farm

One process that significantly contributes to nitrogen losses and therefore climate change and damage to ecosystems is nitrification (conversion of ammonia to nitrate ions). For this, researchers and farmers now aim to reduce nitrogen losses through nitrification management.

“The losses of applied nitrogen fertilizers are mainly due to the action of a specific group of unicellular microorganisms (bacteria and archaea) called nitrifiers, which convert ammonium nitrogen into nitrate. If these microbial conversions are slowed down, more efficient management of nitrogen in the soil will be achieved and the environmental footprint of synthetic fertilizers will be reduced.” explains Ms. Papadopoulou.

This retardation can be achieved through the use of a series of chemical compounds called nitrification inhibitors that are used in conjunction with nitrogen fertilizers. These are a small number of compounds that present large variations in their effectiveness (depending on the soil to which they are applied). However, little is known about its mechanism of action, its environmental fate, and its potential toxic effects in the environment.

Nitrification inhibitors are being put under the microscope by researchers at the University of Thessaly Department of Biochemistry and Biotechnology and Department of Environment, who are developing innovative and environmentally friendly strategies to increase the efficiency of nitrogen fertilizers. and limit your environmental footprint.

“There have been fascinating observations of the root systems of some plants inhibiting nitrification. This opened up a management option to reduce nitrofication rates in the environment using genetic approaches. The use of biological nitrification inhibitors that plants produce through their roots is a promising practice to slow down the nitrogen cycle and mitigate climate change.” says Professor of Environmental Microbiology and Biotechnology of the Department of Biochemistry and Biotechnology of the University of Thessaly, Mr. Dimitrios Karpouzas, adding that the specific research group is looking for new innovative synthetic and biological nitrification inhibitors with the prospect of direct use in modern agricultural practice.

The Professor of Environmental Microbiology and Biotechnology of the Department of Biochemistry and Biotechnology of the University of Thessaly Mr. Dimitrios Karpouzas

The team has already discovered a new synthetic nitrification inhibitor with specific activity against nitrifying archaea and, in collaboration with other research groups from Austria, France and Canada, is studying its mechanism of action at the biochemical level. At the same time, it is collaborating with private entities to develop new fertilizers that will contain mixtures of nitrogen inhibitors or new biological nitrogen inhibitors with the aim of maximizing the use of nitrogenous fertilization in agriculture and limiting its environmental footprint.

These research actions are coordinated by the University of Thessaly and funded by the EU through the ACTIONr program with a total budget of 1.5 million euros, but also through private bodies such as the Grantham Foundation, USA ( $1.1 million) that invests in this effort and in general in the development of new tools and innovative strategies to mitigate climate change.

“What is worth mentioning is that our research group has one of the richest collections of nitrifying microorganisms in the world. Based on this collection, it has developed a series of innovative tools and services for the evaluation of new nitrification inhibitors but also for the ecotoxicity analysis of new biocidal compounds such as agricultural and veterinary drugs.concludes Professor Karpouzas