Everything we eat depends on agriculture. Producing food depletes the soil of nutrients essential for plant growth. This is why agricultural production today relies on synthetic fertilisers, which are applied to replenish these nutrients.
This reliance presents a problem as the world races to decarbonisation: ammonia production is the chemical process that most emits CO2 globally: 450 megatons (Mt) per year. Finding other ways to produce ammonia is essential to reach climate targets. But carbon dioxide is not the only problem with fertiliser use or our current agricultural systems. And in addressing climate change, we must take care not to shift the burden to other systems.
The world demand for nitrogen as fertiliser has surpassed 100 Mt annually and is expected to reach 140 Mt by 2030.
Recognising this, addressing the climate crisis becomes an opportunity to redesign our systems, tackle multiple issues - food security, biodiversity loss, the ecological crisis - and build a better planet for future generations.
Clean ammonia: avoiding environmental problem shifting
Generating renewable energy for hydrogen production requires land and water, depending on the technology - bioenergy is especially demanding. Extracting materials to produce solar panels or wind turbines degrade ecosystems and harm biodiversity. Deployment of these technologies can put pressure on wildlife. And producing hydrogen from electrolysis also demands water.
The choice of technology and site, proper environmental impact studies, careful choice of renewable energy and hydrogen partnerships, and having a local communities-centric view when developing projects are all essential to ensure that clean ammonia is produced without shifting the burden to other planetary systems that sustain life.
Nitrogen: the quick fix with a long tail
In general the current incentive structure in agriculture means we are applying more nitrogen to the soil than plants can absorb. About half of the nitrogen is lost to air, water and soil, disbalancing the natural cycles and causing harm to ecosystems and biodiversity.
- Water: Nitrogen that reaches lakes, rivers and other water bodies feeds algae and plants, which grow excessively, preventing light from reaching the bottom and consuming the oxygen that other plants, fish and animals need to survive. This process, called eutrophication, makes these ecosystems wither and die. And, when these nutrients reach coastal areas or the sea, they are a major source of ocean acidification, harming sea life and ocean ecosystems like coral reefs. This pollution also affects the availability of freshwater.
- Atmosphere: One way by which nitrogen reaches the oceans is when ammonia emissions from fertiliser that was spread on fields end up deposited to the ocean. There are also other emissions from fertiliser.
About 2.5% of the nitrogen that is lost in soil is broken down by bacteria producing nitrous oxide (N2O), a greenhouse gas 298 times more powerful than carbon dioxide in causing climate change. This gas, along with nitric oxide (formed when N2O reaches the stratosphere), are currently the most important ozone-depleting emissions.
Other forms of nitrogen that are lost to the atmosphere due to production and application of fertilisers such as ammonium, nitrate, organic nitrogen, etc. are significant contributors to aerosol loading.
Carbon dioxide can also be emitted from fertilisers. Urea, the most commonly used fertiliser today, is made by binding CO2 with ammonia. This CO2 is released when urea is applied to soil, in a total of 130MtCO2/year. - Soil: Farming nitrogen usage and soil health is a layered topic. If on the one hand they replenish nutrients that were consumed to make plants grow, fertilisers also can negatively impact soil health, releasing carbon into the atmosphere. Fertiliser use is also associated with industrial, agricultural practices such as tillage, monocultures and the use of pesticides, which are not favourable for soil health.
For these reasons, effects on land usage are similarly complex. Agriculture is the planet’s single most extensive form of land use. At a basic level fertilisers significantly reduce the amount of land we need for agriculture. This also has positive repercussions for biodiversity. But this effect is uncertain and depends on enforcement of deforestation policies.
If we can harness the power of clean ammonia in situ, replacing perverse incentives to over-fertilise and deforest, while prioritising land restoration, we could reduce the land given up by the biosphere to farming. Part of the solution is changing the way we use fertilisers.
Reducing N2O emissions - Salving the Sting in the Tail
N2O emissions can be reduced by changing fertiliser formulations, such as using slow release fertilisers, management practices such as conservation tillage, and method of application, such as deep or spread applications throughout the season. Strategies such as these, along with wider changes in the agri-food system, could reduce fertiliser emissions by 70%.
Reducing fertiliser loss or use - Efficiency as an impact tool
Going at the heart of the problem means two things: reducing fertiliser loss, and using less fertiliser altogether. Adequately matching fertiliser input with soil needs can be achieved with the 4R nutrient stewardship management practice: right source, right rate, right time, right place.
Management practices such as “low tech” tools for site specific nitrogen management; integrated nitrogen management combining chemical fertilisers with indigenous sources of N; green manuring by using legume crops which fix atmospheric N in the soil; conservation management; proper crop rotations; genetic improvement, and precision farming all can help achieve these goals.
All of these dynamics of agricultural production significantly impact ecosystems and biodiversity. To achieve food security while reducing planetary impacts, we need to reinvent the way we do agriculture.
Sustainable agricultural transition: a collaborative approach
Some pillars of this transformation have been mentioned, such as minimal tillage and diversity in cultures. Others include integrated systems of crops with livestock and trees, such as agroforestry, expanding regenerative agricultural systems, avoiding pesticides, promoting research through farmer networks and overall taking into account externalities of food systems.
Decarbonising the fertiliser sector, increasing fertiliser efficiency and reducing nitrogen inputs are important pieces of this puzzle. But it is also important to understand these solutions in the context of food systems and dietary habits, such as reducing food waste and demand for animal products.
Combining all these strategies together means not having to implement a single measure at maximal coverage, while still increasing the sustainability of the global food system.
Clean ammonia is arguably our most powerful tool, an archimedes lever in terms of agricultural emissions reduction, but it is only one tool in a broader climate and biodiversity action toolkit. Innovation and collaboration with positive actors across the whole food system is how we pave a way forward to regenerative food production and practices.
Claudia Luiza Manfredi Gasparovic | Nium
References:
1. World fertiliser trends and outlook to 2022.
2. Ammonia Technology Roadmap..
3. The contribution of manure and fertiliser nitrogen to atmospheric nitrous oxide since 1860.
4. Soil Management Practices to Mitigate Nitrous Oxide Emissions ...
5. Nitrous oxide (N2O): the dominant ozone-depleting substance emitted in the 21st century.
6. Global influence of synthetic fertilisers on climate change.
7. Agriculture production as a major driver of the Earth system exceeding planetary boundaries.
8. Reducing emissions from fertiliser use.
9. Strategies for improving nitrogen use efficiency: A review.
10. Nitrogen and the future of agriculture: 20 years on.
11. Secretariat of the Convention on Biological Diversity, Montreal. Global Biodiversity Outlook 5.
12. Nitrogen emissions along global livestock supply chains.
13. Strategies for feeding the world more sustainably with organic agriculture.
