Green hydrogen is not a silver bullet to decarbonize the fertilizer industry

Earlier this year, Yara, the world’s largest ammonia distributor, cancelled some of their green hydrogen projects citing cost concerns. This follows the trend of companies scrapping or scaling back their clean hydrogen plans, no doubt escalated by the early retirement of the 45V clean hydrogen tax credit.  

Yara planned to use this green hydrogen to produce ammonia, made by pairing hydrogen with nitrogen from the air. That ammonia would then likely be used to make fertilizers rich in nitrogen, a crucial nutrient for plant growth. While Yara still has some plans in the works for green hydrogen procurement, the slowdown of production development could cause major hurdles in the ammonia industry’s proposed decarbonization strategy.  

Even if green hydrogen could be produced as abundantly as to meet this projected demand, switching from conventional ammonia to green ammonia wouldn’t yield the robust emissions reductions the industry is hoping for. 

Decarbonizing ammonia production 

Currently, ammonia production emits 500 million metric tons of CO2 every year. These sky-high emissions stem from two aspects of production. First, the hydrogen needed during production is typically grey hydrogen, derived from fossil fuels. Second, the process of pairing this hydrogen with nitrogen to create ammonia is extremely energy intensive. Cleaning up ammonia production involves replacing grey hydrogen with green hydrogen, which is created using renewable energy, then powering the whole production process with renewables as well. 

One company, Talusag, has already begun producing ammonia from solar electricity at small pilot facilities in Iowa. Whether these projects will continue remains to be seen. Their economic viability relies heavily on the 45V clean hydrogen tax credit, which will now sunset five years earlier than it was initially slated to.   

Green ammonia isn’t inherently climate-friendly. It carries the same concerns as green hydrogen: the potential to divert renewable energy away from more beneficial uses, the extensive amounts of freshwater needed for the process, and hydrogen and ammonia gas leakage throughout the supply chain.   

Companies are using the term “clean ammonia” very broadly. Sometimes, it refers to “blue ammonia”, which is made with fossil fuels but is paired with carbon capture and storage (CCS). CCS is a dubious technology that comes with its own host of concerns.  

Other times, things are a bit more veiled.  

Just a few months ago, an investigation by The Guardian and DeSmog.org found that Yara’s only US-based ammonia plant, which they claimed was sourcing “by-product” hydrogen from a neighboring chemical facility, was actually using hydrogen created from natural gas. The use of “by-product” hydrogen was supposed to help reduce the carbon footprint of this Texas plant, but instead the natural gas used to make the hydrogen was pulled from the #1 most polluting gas production site in the world, the Permian Basin. Another one of Yara’s supposedly clean ammonia plants is powered with biomethane, an alternative fuel whose carbon neutrality is frequently questioned.   

Even if green ammonia was produced in a truly carbon-free manner with limited strain on water resources and a completely leak-proof system (a nearly impossible task), a different problem would still loom over the whole supply chain. 

Ammonia and the nitrogen cycle 

The nitrogen cycle is a combination of ecological processes that takes stable nitrogen gas (N₂) from the air and turns it into forms of nitrogen that plants can absorb, called reactive nitrogen (N_r). Nitrogen is the most important nutrient for plant growth. The N_r is eventually returned to its stable form as N₂, which makes up 80 percent of the earth’s atmosphere.  

Man-made additions to N_r levels in the past century, like the nitrogen oxides (NO_x) released when fossil fuels are burned, have thrown this naturally balanced cycle completely out of whack, doubling the amount of N_r in global circulation. This surplus has devastated ecosystems and lead to air pollution, algae growth in freshwater, ocean acidification, and biodiversity loss.  

Ammonia is a major contributor to anthropogenic nitrogen excess. Around half of ammonia emissions come from animal manure, but a significant portion of emissions also come from fertilizers. When ammonia-based fertilizers are spread across crops, less than 50 percent of the available nitrogen is absorbed by plants, leaving the rest to pollute the surrounding air, water, and soil. Some of this ammonia surplus also gets broken down and oxidized by bacteria in the soil, producing nitrous oxide (N₂O), a greenhouse gas almost 300 times more potent than carbon dioxide and another form of N_r. 

As countries consistently fall short of carbon reduction goals, nitrogen limits tell a similar story. A “nitrogen crisis” in the Netherlands caused by high-density farming saw multiple failed attempts at regulation, prompting the government to delay reduction targets by 5 years. This is despite a court ordering them to stay on track earlier this year.  

Other European countries have found more success, with ammonia strategies in England and Germany both proving more fruitful. The US lags behind, with no comprehensive strategy to reduce ammonia emissions and active attempts to stymie fertilizer efficiency strategies.  

With the slated increase in ammonia production, and the continued consolidation of farms across the world, reducing N_r levels will take a major overhaul of agricultural systems and a collaborative effort from governments and farmers alike. 

Decarbonizing food systems 

The discovery of ammonia production and the fertilizers it can make revolutionized food production and supported the rapid population growth of the 20^th century. It’s estimated that 50 percent of the world’s population relies on food made possible by ammonia. But whether to decrease ammonia emissions or continue to sustain global food production is a false dichotomy.  

Countless studies show that increased fertilizer efficiency (i.e. enabling crops to absorb more of the nitrogen in fertilizers) and alternative crop management practices can decrease nitrogen emissions while continuing to bolster crop yield. While green ammonia may play a small role in this transition, new discoveries in plant, soil, and microbe biology will help to enable farms to use less fertilizer and see improved production. 

Unfortunately, reducing the use of fertilizers won’t sit well with the close to $300-billion-dollar fertilizer industry, whose lobbyists have powerful influence on climate and agriculture policy.  

This influence means that ammonia facilities just keep proliferating, with 38 new planned ammonia facilities in the US this year, many of which also include hydrogen plants. This boom is due in part to ammonia’s presence in the nascent clean shipping fuel arena, but that’s a topic for another blog. Decarbonizing food systems must be a multi-pronged approach, and green ammonia might not be the star that the fertilizer industry is betting on.