World Soil Day – what Nitrogen and the Goldilocks principle have in common
Feeding 10 billion people in 2050 will require higher crop yields and this will necessitate a Goldilocks approach to Nitrogen – too much and the planet suffers, too little and people will starve. The healthy soil that results from the sustainable use of nitrogen will have the added benefit of helping to absorb carbon. The global food system needs to be transformed to address the climate crisis as well as ensuring healthy diets for all – ensuring nitrogen (as well as carbon) stays within its planetary boundaries will be key.
The Nitrogen Problem is Complicated
The climate challenge is well understood. We know emitting carbon dioxide is warming the planet, we know the main sources of emissions and we have scenarios of what will happen if we fail to decarbonise our economy in time. A tonne emitted in Australia is the same as a tonne emitted in China, the US and elsewhere. It all impacts global warming and climate change in much the same way.
Unfortunately, the nitrogen problem is harder to understand and could be tougher to solve, but it is also vitally important. Nitrogen is an essential component in the production of food – without it plants cannot grow. Nitrogen forms a key element of the amino acids which form the building blocks for the proteins in plants and ultimately provide us with nutrition when we eat them.
To feed 10 billion people in 2050 will require a lot of protein and from a land-use perspective, plants provide the most efficient way to produce this. But this means that as well as shifting our diets we will need to increase crop yields and this will require nitrogen.
We Need a Localised Goldilocks Model
The quantity of nitrogen required depends on the crop being grown. Some, such as soybeans, take nitrogen from the air and so need very little nitrogen fertiliser input. Others do not fix nitrogen in this way and so need larger amounts of external input – the challenge is to apply the right amount to meet the needs of the crop but not to exceed this. In many higher income countries this limit is often exceeded, either by applying too much nitrogen, or by using it at the wrong time.
Nitrogen, like carbon dioxide, can be a pollutant. When too much nitrogen fertilizer is applied to soil the excess nitrogen can run-off from fields leaching into waterways poisoning them and causing major damage to coral reefs and destroying fisheries.[i], [ii] Excess nitrogen is also emitted from the soil into the atmosphere as ammonia or nitrous oxide (a greenhouse gas).
Figure 1: Simplified Nitrogen Cycle [iii]
It is estimated that 32% of nitrogen used in food production is lost from fields due to leaching and gaseous emissions.[iv] This equates to approximately 55 million tonnes of nitrogen fertiliser lost per year, or USD 27 billion using an average price of USD 495 per tonne from 2020 (fertiliser prices have since spiked and reached over double this value).[v] The inclusion of food waste (estimated to amount to a third of total food production) in the nitrogen loss calculation would put this value higher still.[vi]
Clearly, as well as poisoning the environment, nitrogen run-off represents a significant loss to the farmers concerned and an avoidable cost to the wider food system.
There are biological limits to the amount of nitrogen that can be allowed into waterways each year. The difficulty with nitrogen, in contrast to carbon dioxide, is that ‘too much’ varies according to local conditions. In general, the concentration of nitrogen in water should not exceed 2.5 mg per litre, but this can vary on a sub-national scale (and governments can set different limits from a legal perspective).[vii]
Nitrogen’s Planetary Boundary
Because the nitrogen concentration limit varies depending upon local conditions calculating a global limit is more challenging (unlike carbon dioxide) but still provides a useful benchmark when assessing the extent of nitrogen pollution. The Stockholm Resilience Centre estimates the current annual quantity of nitrogen being used in agriculture and industry globally as 150 million tonnes compared to their estimate of the planetary boundary for nitrogen as 62 million tonnes per year – 140% above the limit.[viii]
However, in practice, nitrogen boundaries vary by geography and need to consider factors such as the crop that is being grown in that region. As a result, reduction is not required everywhere. Where over-application of fertilisers is more common in higher income countries, the opposite is true for many lower income ones. In fact, in many countries, the nitrogen input falls below what is required for reaching optimum yields in that region. As a result, some producers, especially in sub-Saharan Africa, consistently fail to reach the yield potential for many of their crops.[ix]
Performance vs. Benchmark
Wheat, a global staple, could contribute 20% of protein consumption as part of a sustainable diet according to a study by the EAT-Lancet Commission. The map below shows countries that are currently below the nitrogen boundary for wheat production (green), and countries that are exceeding their boundary (red).[x] Countries in red need to improve how they manage and apply nitrogen fertiliser to reduce the impacts of excess nitrogen polluting the environment. Countries in green have the opportunity to sustainably intensify their nitrogen fertiliser use and potentially increase their wheat production.
Figure 2: Countries Exceeding their Nitrogen Boundary for Wheat Production.
One of the reasons that many farmers in lower income countries are failing to achieve higher yields is access to affordable nitrogen fertiliser and timely information regarding the quantity and timing of its application. Solving these challenges would create economic opportunities that would help to increase food security and raise many people out of poverty.
Fixing the Nitrogen Problem
To reduce the impacts of nitrogen pollution, there are two main solutions – develop new ways to clean up the mess or address the problem at source.
Cleaning up the mess is difficult but could present investment opportunities. For example, as well as providing a source of income, oyster beds filter nitrogen (and other pollutants) out of the water and, if used in the right context, could provide ecosystem services valued at between USD 5,500 and USD 99,000 per hectare.[xi] Unless we tackle the emissions side of the equation, these types of nature-based solutions will be needed in abundance if we are to keep within the boundaries nature has set for us.
However, the scale of the nitrogen pollution problem means that addressing it at source will be essential. Regenerative agricultural practices are widely recognised as providing at least part of the solution. No-till agriculture, crop rotation, and the use of cover crops can help to reduce the need for nitrogen and other inputs, while maintaining yields and increasing the resilience of the soil to droughts and floods. The problem with deploying these techniques can be attracting the funding required to invest in new machinery or purchase cover crops that don’t provide a new source of income for the farm.
These techniques have a climate benefit as well because they sequester carbon. Improved soil management could sequester carbon at a cost of USD 57 per tonne.[xii] This presents an opportunity for developed countries to invest in least developed countries as a means of mitigating global GHG emissions while providing local benefits in the form of improved food production and security. There is an opportunity as well for investors (and companies) to fund improved agricultural practices across the globe as part of a holistic approach to nature-based solutions that help alleviate climate change and also enhance biodiversity and reduce nitrogen pollution.
Addressing nitrogen pollution at source has the potential to be self-financing given the fact the pollution equates to inefficient use of resources and a loss to the producers concerned. A report by CREO calculates that approximately USD 23 billion per year will be required until 2050 to scale regenerative farming practices, a little less than the value of annual fertiliser loss.[xiii], The economic case is even stronger when the financial costs are balanced against the benefits that healthy soils bring in terms increased crop yields, reduced soil erosion (and other costs such as flooding), and the potential for healthy soil to sequester carbon.
The Double Benefit – Food and Climate
Feeding 10 billion people in 2050 will require far more efficient use of resources in our global food system than is currently the case. Ensuring that nitrogen is used wisely so that it remains within local boundaries will have multiple benefits – helping with the climate challenge, providing food for a growing population and with our efforts to restore nature.
December 5th is World Soil Day. It is a good reminder that investors looking for opportunities might do well to look at the soil beneath their feet.
[ii] US EPA (2020) The Effects: Dead Zones and Harmful Algal Blooms. [Accessed on 18/11/2021] Available from [https://www.epa.gov/nutrientpollution/effects-dead-zones-and-harmful-algal-blooms]
[iii] UNL (2021) Nitrogen Dynamics. University of Nebraska-Lincoln [Accessed 24/11/2021] Available from [https://water.unl.edu/article/animal-manure-management/nitrogen-dynamics]
[iv] Liu et al. (2016) Reducing Human Nitrogen Use for Food Production. Nature. Scientific Reports.
[v] AgriLife (2021) Fertilizer Prices Continue Record Climb. [Accessed on 18/11/2021] Available from [https://agrilifetoday.tamu.edu/2021/11/09/fertilizer-prices-continue-record-climb/]
[vii] de Vries et al. (2013) Assessing Planetary and Regional Nitrogen Boundaries Related to Food Security and Adverse Environmental Impacts. Environmental Sustainability.
[x] Planet Tracker Analysis
[xi] Grabowski et al. 2012 Economic Valuation of Ecosystem Services Provided by Oyster Reefs. Bioscience [Accessed on 30/11/2021] Available from [https://academic.oup.com/bioscience/article/62/10/900/238172/]