Food has a climate problem: nitrous oxide emissions accelerate with growing demand

At the heart of this challenge is the prodigious use of fertilizers and the growing demand for meat from a growing global population.

As Earth, climate and atmospheric scientists, we track global greenhouse gas emissions and have just released the most comprehensive assessment to date of a powerful greenhouse gas from of food production: nitrous oxide, or N₂O.

After carbon dioxide and methane, N₂O is the most important greenhouse gas released by humans into the atmosphere. Although there is less N₂O than carbon dioxide in the atmosphere, it is 300 times more powerful at warming the planet and stays in the atmosphere, trapping heat, for more than a century. Today, atmospheric levels of N₂O are about 25% higher than before the industrial revolution, and they continue to increase at an accelerating rate.

The atmospheric concentration of N₂O remained fairly stable until the 1800s, when it began to increase rapidly. Measured in Antarctic ice cores (green) and by modern measurements (red). BoM/CSIRO/AAD

We found that globally, fertilizers and livestock manure management are driving increased N₂O emissions and their rapid accumulation in the atmosphere. It’s more than a climate problem. N₂O also depletes the ozone layer, which protects humans from harmful solar radiation. And nitrogen runoff from fields pollutes waterways, increasing harmful algae blooms and creating oxygen-depleted dead zones.

The increase in N₂O emissions is alarming, but people today have the knowledge and many technologies to reverse the trend.

Where do N₂O emissions come from?

Before the Industrial Revolution, natural sources of N₂O from microbes living in forest soils and oceans were roughly equal to natural sinks that consumed N₂O in the air, so atmospheric concentrations of N₂O were relatively constant .

However, the human population and its demand for food have increased rapidly, upsetting this natural balance.

We found that human activities alone have increased N₂O emissions by 40% over the past four decades, with agriculture contributing about 74% of total anthropogenic N₂O emissions.

The largest human sources of N₂O are agriculture, industry, and the burning of forests or agricultural waste.

Sources of annual N₂O emissions and evolution during the decade 2010-2019. Measured in millions of metric tons. Global Carbon ProjectCC BY

Nitrogen fertilizers, widely used in agriculture, are one of the main contributors. Fertilizers are responsible for 70% of total agricultural N₂O emissions worldwide. Animal waste from intensive livestock farming contributes around 30%. Aquaculture, like fish farming, is a smaller but rapidly growing source, particularly in China where it has increased twenty-five-fold over the past 40 years.

Besides agriculture, industrial processes such as the production of nylon, explosives and fertilizers, as well as the combustion of fossil fuels also contribute to N₂O emissions, but to a lesser extent than agriculture.

N₂O emissions by country

Emissions vary considerably between countries for a number of social, economic, agricultural and political reasons.

Emerging economies, such as China and India, have experienced a sharp increase in N₂O over the past four decades, as they have increased agricultural productivity to meet the growing food demand of their populations.

China is the largest producer and user of chemical fertilizers. Its Action Plan for Zero Growth in Fertilizer Use by 2020, published in 2015, helped reduce these N₂O emissions. However, its industrial N₂O emissions continued to increase.

In Brazil and Indonesia, the felling and burning of forests to make way for crops and livestock, combined with increasingly intensive agricultural practices, have exacerbated nitrogen losses from natural sources and amplified carbon emissions. greenhouse gas.

Africa has the opportunity to increase its food production without increasing nitrogen fertilization. However, North African countries have more than tripled their emissions growth over the past two decades, mainly due to substantial growth in livestock in Africa.

However, some regions have managed to reduce some of their N₂O emissions through more sustainable practices.

The European Union, Japan and South Korea have all successfully reduced their anthropogenic N₂O emissions over the past 40 years, although they remain significant emitters globally; reductions came largely from the chemical industry in the 1990s. Their use of nitrogen in agriculture also became more efficient; however, they still have work to do. Their emissions from direct application of fertilizers and manure have only slightly decreased and have recently stabilized.

In the United States, agricultural emissions continue to increase, while industrial emissions have decreased slightly, leaving overall emissions rather stable.

How to reduce N₂O emissions

Meeting the challenge of reducing N₂O emissions requires a combination of policy interventions, technological innovation and individual actions. For example:

• Policies can encourage farmers to adopt nitrogen-saving practices, optimize fertilizer use, and reduce N₂O emissions and other forms of nitrogen pollution through various incentive programs.

• Precision agriculture techniques, including the use of remote sensing and satellite GPS-guided equipment, can help farmers vary the rate of fertilizer applied to optimize nutrient management and minimize nitrogen losses , thus reducing N₂O emissions.

• The development and adoption of nitrogen-efficient fertilizers, such as controlled-release formulations and nitrification inhibitors, also offer promising ways to reduce nitrogen runoff and curb N₂O emissions from agricultural soils.

• Likewise, innovations in livestock management, such as feed supplements and improved waste management practices, can reduce the amount of N₂O coming from livestock.

• Industries, particularly nylon and fertilizer production, can install existing, affordable technologies to reduce almost all of their N₂O emissions. It’s an easy win for implementation and climate. Most of the world has already done so, leaving China and the United States responsible for most of the remaining industrial N₂O emissions.

• Consumers can also incorporate more plant-based foods into their diet. You don’t need to go vegan unless you want to, but reducing the frequency and portion size of meat and dairy consumption can be healthy for you and the environment. Eco-friendly practices like composting food waste and reducing fertilizer use on lawns also help.

Overall, a comprehensive approach combining policy, technology and individual actions is needed to tackle N₂O emissions and combat climate change. As governments, industries and citizens all work towards a sustainable future, these strategies can help ensure food security and environmental sustainability for future generations.

Hanqin Tian, ​​Director and Institute Professor, Center for Earth System Science and Global Sustainability, Schiller Institute for Integrated Science and Society, Boston College; Éric Davidson, professor, University of Maryland, Baltimore; Pep Canadell, Chief Research Scientist, CSIRO Environment; Executive Director, Global Carbon Project, CSIROand Rona Louise Thompson, Senior Scientist, Norwegian Air Research Institute

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