Nitrogen fertilisers are incredibly efficient, but they make climate change a lot worse



Sustainable farming can reduce nitrous oxide emissions.
eutrophication&hypoxia/Flickr, CC BY-SA

Pep Canadell, CSIRO; Hanqin Tian, Auburn University; Prabir Patra, and Rona Thompson, Norwegian Institute for Air Research

Nitrous oxide (N₂O) (more commonly known as laughing gas) is a powerful contributor to global warming. It is 265 times more effective at trapping heat in the atmosphere than carbon dioxide and depletes our ozone layer.

Human-driven N₂O emissions have been growing unabated for many decades, but we may have been seriously underestimating by just how much. In a paper published today in Nature Climate Change, we found global emissions are higher and growing faster than are being reported.




Read more:
Nitrogen pollution: the forgotten element of climate change


Although clearly bad news for the fight against climate change, some countries are showing progress towards reducing N₂O emissions, without sacrificing the incredible crop yields allowed by nitrogen fertilisers. Those countries offer insights for the rest of the world.

N₂O concentrations (parts per billion) in air from Cape Grim Baseline Air Pollution Station (Tasmania, Australia) and air contained in bubbles trapped in firn and ice from the Law Dome, Antarctica. N₂O concentrations from these two sites reflect global concentrations, not local conditions. Source: BoM/CSIRO/AAD.

The Green Revolution

There are a number of natural and human sources of N₂O emissions, which have remained relatively steady for millennia. However, in the early 20th century the Haber-Bosch process was developed, allowing industry to chemically synthesise molecular nitrogen from the atmosphere to create nitrogen fertiliser.

This advancement kick-started the Green Revolution, one of the greatest and fastest human revolutions of our time. Crop yields across the world have increased many times over due to the use of nitrogen fertilisers and other improved farming practices.




Read more:
The next ‘green revolution’ should focus on hunger – not profit


But when soil is exposed to abundant nitrogen in its active form (as in fertilizer), microbial reactions take place that release N₂O emissions. The unrestricted use in nitrogen fertilisers, therefore, created a huge uptick in emissions.

N₂O is the third-most-important greenhouse gas after carbon dioxide and methane. As well as trapping heat, it depletes ozone in the stratosphere, contributing to the ozone hole. Once released into the atmosphere, N₂O remains active for more than 100 years.

Tracking emissions from above

Conventional analysis of N₂O emissions from human activities are estimated from various indirect sources. This include country-by-country reporting, global nitrogen fertiliser production, the areal extent of nitrogen-fixing crops and the use of manure fertilisers.

Our study instead used actual atmospheric concentrations of N₂O from dozens of monitoring stations all over the world. We then used atmospheric modelling that explains how air masses move across and between continents to infer the expected emissions of specific regions.

We found global N₂O emissions have increased over the past two decades and the fastest growth has been since 2009. China and Brazil are two countries that stand out. This is associated with a spectacular increase in the use of nitrogen fertilisers and the expansion of nitrogen-fixing crops such as soybean.

We also found the emissions reported for those two countries, based on a methodology developed by the Intergovernmental Panel on Climate Change, are significantly lower than those inferred from N₂O levels in the atmosphere over those regions.

This mismatch seems to arise from the fact that emissions in those regions are proportionally higher than the use of nitrogen fertilizers and manure. This is a departure from the linear relationship used to report emissions by most countries.

There appears to be a level of nitrogen past which plants can no longer effectively use it. Once that threshold is passed in croplands, N₂O emissions grow exponentially.

N₂O emissions from agriculture estimated by using the emissions factors approach of the IPCC (blue), the calculated emission factor in this study (green), and the average of the atmospheric inversions in this study (black).
Thompson et al. 2019 Nature Climate Change

Reversing the trends

Reducing N₂O emissions from agriculture will be very challenging, given the expected global growth in population, food demand and biomass-based products including energy.

However, all future emission scenarios consistent with the goals of the Paris Agreement require N₂O emissions to stop growing and, in most cases, to decline – between 10% and 30% by mid-century.

Interestingly, emissions from the USA and Europe have not grown for over two decades, yet crop yields across these regions increased or remained steady. Both regions have created strong regulations largely to prevent excess accumulation of nitrogen in soils and into waterways.

These areas and other studies have demonstrated the success of more sustainable farming in reducing emissions while increasing crop yields and farm-level economic gains.

A whole toolbox of options is available to increase nitrogen use efficiency and reduce N₂O emissions: precision applications of nitrogen in space and time, the use of N-fixing crops in rotations, reduced tillage or no-tillage, prevention of waterlogging, and the use of nitrification inhibitors.




Read more:
A new way to curb nitrogen pollution: Regulate fertilizer producers, not just farmers


Regulatory frameworks have shown win-win outcomes in a number of countries. With intelligent adaptions to different nations’ and regions’ needs, they can also work elsewhere.The Conversation

Pep Canadell, Chief research scientist, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO; Hanqin Tian, Director, International Center for Climate and Global Change Research, Auburn University; Prabir Patra, Senior Scientist, Dy. Group Leader, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and Rona Thompson, Senior scientist, Norwegian Institute for Air Research

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

You’ve heard of a carbon footprint – now it’s time to take steps to cut your nitrogen footprint



File 20180712 27042 agmksa.jpg?ixlib=rb 1.1
Transport and livestock are both significant contributors to nitrogen pollution.
Annalucia/Shutterstock.com

Ee Ling Ng, University of Melbourne; Deli Chen, University of Melbourne, and Xia Liang, University of Melbourne

Nitrogen pollution has significant environmental and human health costs. Yet it is often conflated with other environmental problems, such as climate change, which is exacerbated by nitrous oxide (N₂O) and nitrogen oxides (NOₓ), or particulate smog, to which ammonia (NH₃) also contributes.

One way to understand our nitrogen use is to look at our nitrogen footprint. This is the amount of reactive nitrogen, which is all forms of nitrogen other than inert nitrogen gas, released into the environment from our daily activities that consume resources including food and energy.




Read more:
Nitrogen pollution: the forgotten element of climate change


Our earlier research showed that Australia has a large nitrogen footprint. At up to 47kg of nitrogen per person each year, Australia is far ahead of the US (28kg per person), the second on the leaderboard of per capita reactive nitrogen emissions. Australians’ large nitrogen footprints are created largely by a diet rich in animal protein and high levels of coal use for energy.

The nitrogen footprint

Our new research, published in the Journal of Cleaner Production, takes this concept further by measuring the nitrogen footprint of an entire institution, in this case the University of Melbourne.

The institutional nitrogen footprint is the sum of individual activities at the workplace and institutional activities, such as powering laboratories and lecture theatres in the case of a university.

We calculated that the university’s annual nitrogen footprint is 139 tonnes of nitrogen. It is mainly attributable to three factors: food (37%), energy use (32%) and transport (28%).

The University of Melbourne’s nitrogen footprint in 2015 and projections for 2020.

At the university, food plays a dominant role through the meat and dairy consumed. Nitrogen emissions from food occur mainly during its production, whereas emissions from energy use come mainly from coal-powered electricity use and from fuel used during business travel.

Cutting nitrogen

We also modelled the steps that the university could take to reduce its nitrogen footprint. We found that it could be reduced by 60% by taking action to cut emissions from the three main contributing factors: food, energy use, and travel.

The good news is if the university implements all the changes to energy use detailed in its Sustainability Plan – which includes strategies such as adopting clean energy (solar and wind), optimising energy use and buying carbon credits – this would also reduce nitrogen pollution by as much as 29%.

Changing habits of air travel and food choices would be a challenge, as this requires altering the behaviour of people from a culture that places tremendous value on travelling and a love for coffee and meat.

Generally, Australians fly a lot compared to the rest of the world, at significant cost to the environment. We could offset the travel, and we do take that possibility into account, but as others have written before us, we should not make the mistake of assuming that emissions offsets make air travel “sustainable”.

The question that perhaps need to be asked, for work travel, is “to travel or not to travel?” Let’s face it, why are so many academic conferences set in idyllic locations, if not to entice us to attend?

Animal products are major contributors to nitrogen emissions, given the inefficiency of conversion from the feed to milk or meat. Would people be willing to change their latte, flat white or cappuccino to a long black, espresso or macchiato? Or a soy latte?




Read more:
Nitrogen from rock could fuel more plant growth around the world – but not enough to prevent climate change


As 96% of the nitrogen emissions occur outside the university’s boundaries, their detrimental effects are invisible to the person on the ground, while the burden of the pollution is often borne far away, both in time and space.

The ConversationBut, as our study shows for the first time, large institutions with lots of staff are well placed to take steps to cut their large nitrogen footprint.

Ee Ling Ng, Research fellow, University of Melbourne; Deli Chen, Professor, University of Melbourne, and Xia Liang, PhD candidate, University of Melbourne

This article was originally published on The Conversation. Read the original article.

Nitrogen pollution: the forgotten element of climate change


Ee Ling Ng, University of Melbourne; Deli Chen, University of Melbourne, and Robert Edis

While carbon pollution gets all the headlines for its role in climate change, nitrogen pollution is arguably a more challenging problem. Somehow we need to grow more food to feed an expanding population while minimising the problems associated with nitrogen fertiliser use.

In Europe alone, the environmental and human health costs of nitrogen pollution are estimated to be €70-320 billion per year.

Nitrogen emissions such as ammonia, nitrogen oxide and nitrous oxides contribute to particulate matter and acid rain. These cause respiratory problems and cancers for people and damage to forests and buildings.

Nitrogenous gases also play an important role in global climate change. Nitrous oxide is a particularly potent greenhouse gas as it is over 300 times more effective at trapping heat in the atmosphere than carbon dioxide.

Nitrogen from fertiliser, effluent from livestock and human sewage boost the growth of algae and cause water pollution. The estimated A$8.2 billion damage bill to the Great Barrier Reef is a reminder that our choices on land have big impacts on land, water and the air downstream.

Lost nitrogen harms farmers too, as it represents reduced potential crop growth or wasted fertiliser. This impact is most acute for smallholder farmers in developing countries, for whom nitrogen fertiliser is often the biggest cost of farming. The reduced production from the lost nitrogen can represent as much as 25% of the household income.

The solution to the nitrogen challenge will need to come from a combination of technological innovation, policy and consumer action.

The essential ingredient

Nitrogen is an essential building block for amino acids, proteins and DNA. Plant growth depends on it; animals and people get it from eating plants or other animals.

Nitrogen gas (N₂) makes up 78% of the air, but it cannot be used by plants. Fertilisers are usually made from ammonia, a form of nitrogen that the plants prefer.

A century after the development of the Haber-Bosch process gave us a way to manufacture nitrogen fertiliser, our demand for it has yet to level off.

The use of nitrogen fertiliser has risen from 11 million tonnes in 1961 to 108 million tonnes in 2014. As carbon dioxide levels continue to rise in the atmosphere, some plants such as grains will also likely demand more nitrogen.

Wheat with and without nitrogen fertiliser.
Deli Chen/ The University of Melbourne

In fact, nitrogen from fertiliser now accounts for more than half the protein in the human diet. Yet some 50% of applied nitrogen is lost to the environment in water run-off from fields, animal waste and gas emissions from soil microbe metabolism.

These losses have been increasing over the decades as nitrogen fertiliser use increases. Reactive nitrogen causes wide-ranging damage, and will cause more damage if nitrogen losses are not reined in.

Faced with a growing population and changing climate, we need more than ever to optimise the use of nitrogen and minimise the losses.

From farm to fork

One way to understand our nitrogen use is to look at our nitrogen footprint – the amount of nitrogen pollution released to the environment from food, housing, transportation and goods and services.

Research by University of Melbourne PhD candidate Emma Liang shows Australia has a large nitrogen footprint. At 47kg of nitrogen per person each year, Australia is far ahead of the US, which came in with 28kg of nitrogen per person.

A high-animal-protein diet appears to be driving Australia’s big nitrogen footprint. The consumption of animal products accounts for 82% of the Australian food nitrogen footprint.

Animal products carry high nitrogen costs compared to vegetable products. Both products start with the same cost in nitrogen as a result of growing a crop, but significant further losses occur as the animal consumes food throughout its life cycle.

The N-Footprint project aims to help individuals and institutions calculate their nitrogen footprints. It shows how we can each have an impact on nitrogen pollution through our everyday choices.

We can choose to eat lower nitrogen footprint protein diets, such as vegetables, chicken and seafood instead of beef and lamb. We can choose to reduce food waste by buying smaller quantities (and more frequently if necessary) and composting food waste. The good news is, if we reduce our nitrogen footprint, we also reduce our carbon footprint.

Back to the farm

In the meantime, efforts to use nitrogen more efficiently on farms must continue. We are getting better at understanding nitrogen losses from soil through micrometerological techniques.

From sitting in the sun with plastic bucket chambers, glass vials and syringes, scientists now use tall towers and lasers to detect small changes in gas concentrations over large areas and send the results directly to our computers.

Eddy covariance tower.
Mei Bai/ The University of Melbourne

We now know nitrification (when ammonia is converted to nitrate) is an important contributor to nitrogen losses and therefore climate change and damage to ecosystems. It is a process researchers – and farmers – are targeting to reduce nitrogen losses.

Nitrification inhibitors are now used commercially to keep nitrogen in the ammonium form, which plants prefer, and to prevent the accumulation of nitrate, which is more easily lost to the environment.

As this technology advances, we are starting to answer the question of how these inhibitors affect the microbial communities that maintain the health of our soil and form the foundation of ecosystems.

For example, our research shows that 3,4-dimethylpyrazole phosphate (better known as DMPP) inhibits nitrification without affecting soil microbial community diversity.

There have also been exciting observations that the root systems of some tropical grasses inhibit nitrification. This opens up a management option to slow nitrification rates in the environment using genetic approaches.

Solving the challenge of nitrogen use will require research into more efficient ways for primary producers to use nitrogen, but it will also need government leadership and consumer choices to waste less or eat more plant protein. These tools will make the case for change clearer, and the task of feeding the world greener.


On December 4-8, leading international researchers are meeting in Melbourne for the 7th International Nitrogen Initiative Conference to discuss the best new solutions to problems in nitrogen use. For a more in-depth look at these issues, visit the INI2016 website or join a range of food and production experts at the Good Food for 9 Billion: Community Forum.

The Conversation

Ee Ling Ng, Research fellow, University of Melbourne; Deli Chen, Professor, University of Melbourne, and Robert Edis, Soil Scientist

This article was originally published on The Conversation. Read the original article.

Could ‘nitrogen trading’ help the Great Barrier Reef?


Jim Smart, Griffith University; Adrian Volders, Griffith University; Chris Fleming, Griffith University, and Syezlin Hasan, Griffith University

Among the increasing sums of money being pledged to help save the Great Barrier Reef is a federal government pledge to spend A$40 million on improving water quality. The Queensland government has promised another A$33.5 million for the same purpose.

One of the biggest water-quality concerns is nitrogen runoff from fertiliser use. It is a concern all along the reef coast, and particularly in the sugar-cane regions of the Wet Tropics and the Burdekin. The government’s Reef 2050 Long Term Sustainability Plan calls for an 80% reduction in dissolved inorganic nitrogen flowing out onto the reef by 2025.

Our recent research suggests that “nitrogen trading” might be worth considering as a flexible economic mechanism to help farmers deliver these much-needed reductions in fertiliser use.

What is nitrogen trading?

You probably already know about carbon trading, which allows polluters to buy the right to emit greenhouse gases from those with spare carbon credits. Nitrogen trading would work in a similar way, but for fertiliser use.

A nitrogen market could offer a flexible way of encouraging farmers to use fertiliser more efficiently, as well as rewarding innovations in farming practice. It could be a useful addition to existing fertiliser-reduction schemes such as the industry-led Smart Cane Best Management Practice. These are making headway but evidently not enough.

A nitrogen market isn’t going to happen tomorrow, but it could be part of a future in which an annual limit (called a cap) is set on the total amount of nitrogen flowing out from river catchments to the reef.

One way to enforce this cap would be to set a limit on fertiliser applications per hectare. Cane farmers would have to manage the best they could with that fixed amount of nitrogen.

But nitrogen trading would offer more flexibility, while still staying under the same total nitrogen cap. Instead of a fixed limit, farmers would receive a certain number of “nitrogen permits” per hectare of cane. Then, if they wanted or needed to, they could buy or sell these permits through a centralised online “smart market”.

How would it work?

Imagine you’re a farmer with a property that sits on good soil. The amount of fertiliser you can apply to your crop must match the number of nitrogen permits you hold. But you know that, on your good land, you would get more profits if you could apply more fertiliser.

To do this you would have to buy extra permits through the nitrogen market. These extra permits would be worth buying as long as they deliver more than enough extra profit to cover the cost.

The total number of permits is limited by the cap – so buyers can only buy extra permits if other farmers are selling them. So who’s selling?

Putting fertiliser onto a field with poor soil won’t increase your profits as much, because a lot of that fertiliser will just run off before the crop can use it. On a bad paddock, nitrogen permits aren’t worth much in terms of extra crop yield, so you might make more money by just selling them to other farmers with good paddocks. That is why trading happens.

The overall effect of this trading would be to switch a significant amount of nitrogen fertiliser away from less profitable, leaky soils, and onto more profitable, less leaky land. As a result, the total nitrogen cap would be distributed more efficiently across the farming landscape.

For individual farmers, the reward for low-nitrogen farming practice is the opportunity to sell unused permits at a profit. This incentive will help to drive ongoing improvement and innovation.

Our simulations suggest that overall sugar cane profits and production would be higher with trading than they would under a fixed per-hectare nitrogen limit – with the same overall cap on the amount of nitrogen hitting the Great Barrier Reef.

Opportunity for the future?

Will it just mean more expensive regulation, green tape and hassle for farmers? Farmers are already signing up to calculate and record actual fertiliser applications paddock by paddock under the Six Easy Steps nutrient management program.

If we’re in a future where the government is monitoring and managing a fixed nitrogen cap anyway, then not much extra work is needed to set up an online trading market.

So could nitrogen trading help the Great Barrier Reef? Maybe. There’s more thinking still to be done, but nitrogen trading schemes are already operating in New Zealand and the United States.

A firm overall limit on fertiliser use seems to be essential for the reef’s survival. The incentives provided by a nitrogen market could give Queensland’s farmers the flexibility they need to thrive in this nitrogen-constrained future.

Graeme Curwen and
Michele Burford of the Australian Rivers Institute at Griffith University contributed to the research on which this article is based.

The Conversation

Jim Smart, Senior Lecturer, Griffith School of Environment, Griffith University; Adrian Volders, Adjunct Professor, Griffith University; Chris Fleming, Associate Professor, Griffith University, and Syezlin Hasan, Research Assistant, Australian Rivers Institute, Griffith University

This article was originally published on The Conversation. Read the original article.