New research shows promise in reducing the carbon emissions of fertilisers

Nitrogen fertiliser is considered one of the most important inventions of the 20th century. But production is dirty, and expensive. A group of scientists think they can change that. Tom Bawden discusses in an article on the inews website.

 

Carbon footprint of gardening slashed after breakthrough in fertiliser emissions

Fruit and vegetables could become cheaper and greener to grow after scientists developed a new method to produce the world’s most common fertiliser.

Nitrogen fertiliser is considered one of the most important inventions of the 20th century. It is thought to support half the world’s population’s food supply, with nearly a million tonnes used on UK farms alone annually.

Currently the most common method of production is the century-old Haber-Bosch process, a chemical reaction that requires extremely high pressures and temperatures up to 500°C to synthesise ammonia, a key fertiliser ingredient.

Haber-Bosch is credited for kickstarting an agricultural revolution but is a big emitter of carbon dioxide.

Now, scientists from US and Saudi Arabia have developed a novel way to produce ammonia, which can be carried out at room temperature and normal pressure.

The new method virtually eliminates the energy requirements and CO2 emissions of Haber-Bosch, the researchers say, paving the way for cheaper production costs with a significantly lower carbon footprint. They hope for it to be commercially available within the next five years.

“This is very exciting because the Haber Bosch process is a significant source of greenhouse gases through its use of fossil fuels,” Sarah Bridle, professor of food, climate and society at York University, who was not involved in the research, told i.

“The new method is more environmentally friendly than current fertilisers, cheaper and could help to ensure that fewer people go hungry in the future,” she said.

“Fertilisers contribute to climate change for two reasons – through their production and because they interact with microbes in the soil to produce nitrous oxide. These two contributions are roughly equal, so if the energy use of the new method is small, it could roughly halve the climate impact of fertilisers,” she said.

Ammonia is produced by combining nitrogen with hydrogen.

While the Haber-Bosch process uses huge amounts of energy to break the powerful bonds that hold nitrogen atoms together, the scientists managed to achieve the same result by passing a cocktail of tiny water droplets, nitrogen gas and iron oxide through a low-tech sprayer.

The method builds on previous research by Professor Richard Zare, of Stanford University, who found that microdroplets of water produce a powerful chemical reaction when hitting hard surfaces – in this case, iron oxide.

Professor Zare said: “We were shocked to see that we could generate ammonia in benign, everyday temperature-and-pressure environments with just air and water and using something as basic as a sprayer.

“Assuming this process can be scaled up, it would represent an eco-friendly new way of making ammonia, which is one of the most important chemical processes that takes place in the world,” he said.

The research also involved scientists from King Fahd University of Petroleum and Minerals in Saudi Arabia.

The Haber-Bosch process, which earned its co-inventor Fritz Haber the Nobel prize for Chemistry in 1918, uses 2 per cent of the world’s energy supply and produces 1 per cent of the world’s total CO2 emissions, according to a study in the journal Nature Sustainability.

Prof Zare said that, in comparison, his team’s method produced negligible emissions and required up to 100 times less energy.

With food production as a whole accounting for a quarter of the world’s greenhouse gas emissions, this kind of reduction on an industrial scale would be a major contribution to lowering the climate impact of what we eat.

Professor Bridle, author of Food and Climate Change – without The Hot Air, said the new method could also prove a “lifesaver for farmers grappling with rapidly increasing fertiliser costs, due to increasing energy prices and the war in Ukraine”.

The Haber Bosch process requires large amounts of methane gas. Since 2021, the cost of ammonia has significantly increased becuase of soaring gas prices, with 70 per cent of Europe’s production halted by November last year, including that of leading UK producer CF Fertilisers.

The World Economic Forum’s 2023 Global Risks Report has warned of a looming worldwide food crisis because of “lagged effect of a price spike in fertiliser”.

Professor Bridle says: “Increased fertiliser prices are a major factor causing farmers to plant less crops this year and apply less fertiliser, which could contribute to food shortages.”

She added that the new technique could also potentially allow poorer countries to reduce their reliance on Russia and China, both major exporters of nitrogen fertiliser.

Adriaan Davidse, an independent researcher who has previously worked with Professor Zare but was not involved in the project, estimated that a large-scale rollout of the new fertiliser process could lead to sustained drop in global food prices of up to 2 per cent.

Professor Zare said he had been approached by a number of venture capital firms interested in backing the project, and his hopeful that the technology can be rolled out worldwide. “My hope is less than five years,” he said.

However, Virgil Percec, professor of chemistry University of Pennsylvania, who is not involved in the project, believes it could be far quicker.

“More than a century ago it took just four years to go from discovery to commercial development with Haber-Bosch, which is much more complex technologically. Today, it may take less than a year,” he said.

The research appears in a new paper in the journal Proceedings of the National Academy of Sciences.

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