Report: Fertilizer responsible for more than 20 percent of total agricultural emissions

As the UN Climate Change Conference (COP26) gets underway in Glasgow, a new report finds that synthetic nitrogen fertilizers are responsible for more greenhouse gas emissions than previously thought, outpacing even the commercial aviation industry. The report, from the Institute for Agriculture and Trade Policy, Greenpeace and GRAIN, urges a swift transition toward more sustainable food production in order to avert the most catastrophic effects of climate change.

Synthetic nitrogen fertilizers are widely used in conventional agriculture to boost productivity. But their production and use takes a huge toll on the environment, emitting carbon dioxide and methane as well as nitrous oxide — an often overlooked but highly potent greenhouse gas that has 265 times more global warming potential than carbon dioxide. The amount of synthetic nitrogen fertilizers used worldwide has grown 800 percent since the 1960s, according to the Intergovernmental Panel on Climate Change. That volume is expected to increase another 50 percent by 2050, the Food and Agriculture Organization of the United Nations (FAO) estimates.

The report is based on new research that has not yet been published but is available as a pre-print. The research team amassed what it says is the most comprehensive data set to date on emissions created by the synthetic nitrogen fertilizer sector. Using data from individual countries, the FAO, and other sources, researchers calculated emissions all along the production chain, from manufacturing to transport to application and even runoff of fertilizer into waterways. Taken together, these emissions amounted to the equivalent of 1,250 million tonnes of CO2 in 2018—more than a fifth of total estimated direct emissions from agriculture worldwide. In comparison, the commercial aviation industry—whose contributions to global warming are well recognized — emitted around 900 million tonnes of greenhouse gasses in 2018.

According to the new analysis, synthetic nitrogen fertilizers alone are responsible for about 2.4 percent of global emissions, which is slightly higher than a previous FAO estimate which attributed about 2.1 percent of total emissions to the sector. Researchers also found that 60 percent of emissions from synthetic nitrogen fertilizers were generated after the products were applied to soil. The rest came from manufacturing — which uses fossil fuels and emits methane — and transportation, which other estimates haven’t always taken into account.

The amount of fertilizer-related emissions likely varies by country. For example, a 2013 paper that assessed emissions from the entire supply chain of synthetic nitrogen fertilizers in China found that these fertilizers account for about 7 percent of all of China’s greenhouse gas emissions, in part because China primarily uses coal in producing nitrogen fertilizers instead of natural gas, which is used elsewhere.

“Clearly, if you account for the entire supply chain of synthetic fertilizer production, it is significant contribution to global emissions, and it needs to be part of the discussion around around meeting global climate targets,” said David Kanter, who is an environmental studies professor at New York University and vice chair of the International Nitrogen Initiative, which aims to optimize the use of nitrogen in food and energy production while minimizing harms to the environment. He was not involved in the research, but said its methodology appeared sound.

Fertilizers also are linked to a host of other environmental ills, including air and water pollution that occurs when the fertilizers aren’t fully used by crops, dead zones and algal blooms in ocean and freshwater ecosystems, and depletion of the ozone layer.

Hanqin Tian, a professor at Auburn University and director of the International Center for Climate and Global Change Research, reviewed the IATP report and said the life-cycle approach taken by the researchers appears to add value to the literature. “It is important to consider the whole picture,” he said.

One of the outcomes of the COP26 negotiations is likely to be some guidance for how countries can cut agricultural emissions as part of their overall emission-reduction pledges, says Shefali Sharma, director of the European office of the Institute for Agriculture and Trade Policy. The summit began on Oct. 31 and is scheduled to end Nov. 12.

Starting in the 1960s with the Green Revolution, governments and intergovernmental organizations like the World Bank have pushed to boost agricultural productivity by increasing the use of fertilizers and pesticides. “That aid could have gone into promoting agroecology or promoting diversified [agricultural] systems,” Sharma said. Instead, she says, it promoted a food system dominated by monocultures and oriented toward exports, exploiting comparative advantages and big yields.

If government policies have led to the current crisis, Sharma says, they could help shape the solution by promoting agro-ecological practices, diversified farming, and other methods that help build healthy soils.

A promising example is the European Union’s Farm to Fork Strategy — a blueprint for a more sustainable food system designed to help the EU meet its goal of becoming climate-neutral by 2050. The strategy calls for a 20-percent reduction of fertilizer use by 2030; it also would increase the area of EU land farmed organically to 25 percent, up from 8.5 percent currently.

The European approach stands in stark contrast to the U.S.’s vision for cutting emissions from the agricultural sector, which relies on high-tech fixes and data-driven “precision agriculture,” which would help farmers apply fertilizers more efficiently but doesn’t set targets for reducing their use. The U.S. strategy does not promote organic farming, which precludes the use of synthetic fertilizers. Less than 1 percent of U.S. farmland is farmed organically.

Both Tian and Kanter said that while it’s essential to reduce synthetic nitrogen fertilizers emissions, any suggestion that they could be entirely phased out is simplistic and could exacerbate food insecurity and habitat loss. Tian said efforts in Europe to reduce fertilizer use, and use it more efficiently, have also reduced the bloc’s nitrous oxide emissions, which offers a promising model for how to address global warming while maintaining agricultural productivity. Instead of across the board cuts, Tian urged a regional approach that takes into account different countries’ agricultural systems and emissions footprints.

Rich countries like Canada and the U.S. have the responsibility to take the lead in cutting their consumption of synthetic fertilizers, Sharma said. “They can do this,” she said. And poorer countries with less productive food systems also need to think about how to transition off of nitrogen fertilizers.

But agribusiness is deeply influential in government and policy circles, she notes. By publishing this report, Sharma hopes to ramp up pressure on governments and regulators to hold the fertilizer industry accountable for its emissions. “We need to put these guys out in the spotlight and get much more focus on them as some of the big contributors to climate change like we have for the fossil fuel companies,” she said.