Fertiliser is intimately linked with fossil fuels.

With some of the oldest and most nutrient-poor soils in the world, Australian farmers rely on artificial fertilisers to grow crops.

Australia imports more than 2 million tonnes of fertiliser each year, according to the UN’s Food and Agriculture Organization.

Most of that fertiliser is literally made from fossil fuels: hydrocarbons like methane are a major ingredient in the world’s most widely used fertilisers.

Alongside the energy needed to produce and transport them, this makes fertiliser supply particularly vulnerable to the war in Iran and the blockage of the Strait of Hormuz.

The current fertiliser shortage in Australia is the third in recent years, after COVID in 2020 and the 2022 Russian invasion of Ukraine also caused supply shocks.

Marit Kragt, a researcher in agriculture at the University of Western Australia, says the farming industry has flagged concerns about fertiliser supply vulnerabilities for years, citing GrainGrowers’ 2023 report as an example.

Australian farms are already using fertiliser sparingly by global standards because of its cost, according to Professor Kragt, with widespread practices like no-till cropping, stubble retention and variable-rate application of fertiliser.

“We’re really punching above our weight, both in environmental performance and [crop] production.”

In the short- to medium-term, deals with other countries, reviving onshore manufacture, and special provisions in the federal budget may help to ease the current shortage.

In the long term, the industry is looking towards technologies that could reduce reliance on imports.

So, are there ways we can disconnect fertiliser from fossil fuels entirely? And how long would it take?

What is fertiliser made from?

There are three main types of fertiliser: nitrogen, phosphorus and potassium.

Phosphorus- and potassium-based fertilisers come from mined sources in Australia and overseas.

“We have maybe a handful of mines [in Australia] where phosphorus and phosphate rock is being mined, same for potassium, but not enough to satisfy domestic demand,” Professor Kragt says.

But the real supply problem currently is for nitrogen fertiliser, which is also the most commonly used worldwide and in Australia by a wide margin.

The simplest nitrogen fertiliser, ammonia (or NH3), is made out of nitrogen and hydrogen atoms.

Nitrogen is easy to get: most of the air around us is nitrogen.

The cheapest source of hydrogen atoms, meanwhile, is fossil fuels, specifically methane or “natural gas”. Most ammonia production worldwide uses methane (CH4), which has four hydrogen atoms, as its source.

Turning air and methane into ammonia is an energy-intensive process, and it releases carbon dioxide (CO2) from the leftover carbon in the methane.

But some of that CO2 proves useful: it’s captured and used to convert ammonia into urea, which is the dominant nitrogen-based fertiliser both in Australia and the world.

So for the last century, our most commonly used fertilisers have needed fossil fuels as a key ingredient.

This is why oil-producing countries, like those around the Strait of Hormuz, are often major producers of fertiliser as well.

But hydrogen and carbon don’t have to come from fossil fuels. 

Green ammonia has potential

Researchers and businesses have been working on alternative ways to make nitrogen fertilisers, and they’re starting to see results.

“There’s no rule in chemistry that says urea must come from fossil fuels,” Rahman Daiyan, a researcher in mineral and energy resources engineering at the University of New South Wales, says.

The most advanced alternative fertiliser source, according to Dr Daiyan, is green ammonia.

Instead of methane, this ammonia uses water (H2O) as its source of hydrogen. The hydrogen is made by using renewable electricity to split the two atoms of hydrogen in water from oxygen.  

Australian startup companies like Jupiter Ionics, PlasmaLeap and Nitricity have developed technologies that can make nitrogen-based fertilisers from air and water with renewable energy, and are working on scaling them up.

Charles Day, CEO of Jupiter Ionics, says he’s received calls from farmers in recent weeks asking when they might be able to buy the company’s technology.

“People are keen to buy one of our machines to make their own ammonia or broader fertilisers. The challenge is we’re still at the lab prototype stage.”

Jupiter Ionics’s prototype technology is designed to be modular, so individual farms can use it to make their own ammonia.

“That opens up the opportunity to make ammonia, which is the precursor for fertilisers, in a distributed manner, closer to where it’s used and also closer to where renewable energy is available.”

Dr Day says the company is aiming to get their technology to market in three to five years.

But for now, it’s much more expensive to make hydrogen out of water than it is to extract it from fossil fuels.

Dr Daiyan says that last week’s federal budget, which halved funding for the next round of the Hydrogen Headstart program, is a bad sign for future hydrogen costs.

“The Hydrogen Headstart program was looking at scaling up hydrogen production, whether it’s for chemical manufacturing, fertiliser manufacturing, or potentially utilisation in other fuels.”

Making green urea is trickier

While some farms use ammonia directly as a fertiliser, many rely on urea or more complex nitrogen mixtures.

But finding a non-fossil fuel source for the CO2 required to convert ammonia to urea is proving difficult.

The most obvious source, according to Dr Day, is biogenic CO2 taken from combusting plants and living matter.

“There’s a lot of biomass in regional centres,” Dr Day says, adding that CO2 captured from the atmosphere may also eventually become a source in the long-term.

His company is also experimenting with adding ammonia to soils in different ways, such as by mixing it with other substances that act as delivery mechanisms. 

Dr Daiyan has been working on a more experimental technology that skips the ammonia step.

His team has found a way to generate urea directly from CO2 and nitrogen pollutants known as NOx gases.

“The nitrogen could come from waste streams such as industrial exhaust, chemical by-products, or even contaminated wastewater,” he says.

The team’s work is still in the early stages, needing detailed analysis before they can scale it up.

There are a host of other fertiliser methods being explored such as organic waste and biomass streams, with some researchers even suggesting extracting urea from urine.

When will we start to move away from fossil fuels?

Whichever method comes out in front, Dr Daiyan says the end goal is to move fertiliser production from large, centralised factories to localised production units, replicating the way energy production is changing.

“This would allow fertiliser to be produced closer to where it is needed, reducing transport costs, improving supply security, and lowering emissions,” Dr Daiyan says.

Professor Kragt says the green ammonia industry can “absolutely” become competitive with existing fossil-based fertilisers.

But she says the process will be very expensive, and take years to achieve.

“If we had invested five years ago, the cost of production would have come down considerably by 2026,” Professor Kragt says.

“We’re talking about considerable investments that really need government support. There’s not a single industry that can do this on their own.”

Dr Day agrees, adding that a significant shift in infrastructure will likely take five to 10 years, at least.

But he also believes that green fertiliser is an unstoppable trend.

“The experience of the last few months has really brought home for people the risks around not having control of your fertiliser supply.”