A Q&A with Nitrogen expert Mark Sutton of the United Kingdom Centre for Ecology & Hydrology
Waste is money. At least that’s what Mark Sutton of the United Kindgom Centre for Ecology & Hydrology wants policymakers to understand. Sutton, who has studied nitrogen pollution for more than three decades, is convinced that there is a way to harvest emitted nitrogen to be reused by farmers as nitrogen fertilizer.
Nitrogen pollution—which Sutton calls the “godfather of pollution,” as you can’t see it as you can the results—is a major challenge for the 21st century, as it contaminates the air, water and land, making it difficult to breathe and altering plant growth. To reduce nitrogen pollution as part of the circular economy, Sutton advocates that we reuse old gas.
Where is Nitrogen found?
Nitrogen (N2) is all around us. Over 78 per cent of our atmosphere is made of nitrogen, it’s the reason the sky is blue and the earth is stable to live in. (If there was only oxygen everything would be on fire.) Nitrogen is a harmless and chemically unreactive gas but if combined with other gases it becomes usable. For example, joined with hydrogen (H2) we get ammonia NH3, which is the raw material for most nitrogen fertilizers. However, ammonia is a major cause of eutrophication and affects biodiversity.
In the combustion of fuel-engines and industry, Nitric Oxide (NO) and Nitrogen Dioxide (NO2) are formed, which are air pollutants and harmful to human hearts and lungs. Nitrate (NO3) is a product of wastewater and widely used in fertilizers and explosives. It makes part of the harmful particulate matter in air, that has major impacts. Nitrous Oxide (N2O) is used in rocket propellants and in the medical sector as laughing gas. But it is a greenhouse gas 300 times more powerful than carbon dioxide and causes depletion of the ozone layer.
Altogether, humans are producing a cocktail of reactive nitrogen that creates pollution. Scientists call it the Nitrogen Challenge. We’ve divided nitrogen’s threats into an acronym of five: WAGES. That stands for water, air, greenhouse gases, ecosystems, and soils/stratospheric ozone depletion.
Nitrogen is one of the most important pollution issues facing humanity. Yet the scale of the problem remains largely unknown and unacknowledged outside scientific circles.
How did we get to have too much nitrogen?
Since the 1950s we’ve doubled the amount of nitrogen compounds in the world following the introduction of mass-produced fertilizer for crops to allow a world population that’s doubled to be fed. With the introduction of cars and heavy industry this has further boosted nitrogen pollution.
The tricky thing about nitrogen as opposed to carbon, is that it is literally everywhere, doing all sorts of things. It's like the godfather of pollution: you see the results, but you don't see the godfather.
What is UN Environment Programme’s work on nitrogen?
The International Nitrogen Management System was launched in 2016 and is led by the Centre for Ecology & Hydrology on behalf of the UN Environment Programme (UNEP) in partnership with the International Nitrogen Initiative. It is something equivalent to the Intergovernmental Panel on Climate Change, but our job is to link the five aspects of WAGES. We are starting to bring together people from all those old disciplines that never used to talk with each other—air pollution, water pollution, greenhouse gases, and so on—and think about which management options can be good for several WAGES aspects. At present there’s no policy process to join up the different environmental work programmes around nitrogen, so the climate people will say, “bring your animals into the farmhouse because on the field they’re emitting harmful nitrous oxide.” While the air people will say, “get the animals out onto the field because otherwise the ammonia emissions will skyrocket.” And this is an example of two parallel universes that don’t talk to each other and yet, funnily enough, it’s the same nitrogen that’s linking them all.
So that’s the big next step: bringing the science and policy together.
How will you do that?
We’re trying to institute a coordination mechanism, under the auspices of UNEP, where all the different UN conventions that exist—air, land, water, climate and stratospheric ozone—will work together to complement their efforts in reducing nitrogen without interfering with each other’s mandates. We talk about this in the 2018/19 Frontiers report.
At the upcoming UN Nitrogen Campaign launch event in Colombo, Sri Lanka 23–24 October—for which Ricky Kej has prepared a nitrogen song—we will work with countries to prepare for this coordination mechanism. Our expectation is that countries will then want to bring this to the fifth UN Environment Assembly in 2021. What we’ve done in preparation for the Colombo event is create a United Nations roadmap for sustainable nitrogen management. This roadmap was presented to the Committee of Permanent Representatives early October at UNEP’s headquarters in Nairobi. There is already a call for the establishment of a working group for the Committee of Permanent Representatives. UNEP is the right body to coordinate this because it’s global and it’s got the mandate for all the WAGES issues.
What can we do to lessen nitrogen pollution?
Some people advocate reducing nitrogen pollution by “denititrying” nitrogen compounds in air or water, thereby converting useful nitrogen forms back to pure atmospheric nitrogen (N2). With our thinking about a joined-up approach we don’t consider that very wise because nitrogen compounds are a good resource if we can use them in the right way, i.e. nutrient recycling. At the moment all of the nitrogen for fertilizer comes from fresh nitrogen from the atmosphere. Imagine a world where fertilizer companies obtained nitrogen from the nitrate already in wastewater or the nitrogen oxides from a chimney. In this way you would capture tonnes of pollution while generating a circular economy for nitrogen.
Let’s take 19th century Paris. Before they invented the flushing toilet, there was a designated city authority collecting people’s excrements and taking them to a factory at the edge of Paris. They would settle it and distill it, get out all the ammonia and put it together with sulfuric acid and make ammonium sulfate fertilizers. They created around 2,000 tonnes of this fertilizer every year from the excrements of Paris.
What is the potential to this approach?
If we add up all the nitrogen pollution lost in the world—200 billion tonnes—putting the health, ecosystem and climate costs aside, we can calculate the potential cash resource by multiplying the pollution quantity by the fertilizer price. At US$1 per kilogram, this leaves you with 200 billion dollars a year of resource to mobilize huge economic innovation.
How can we adopt it?
All the technologies at the moment are using energy to destroy the nitrogen resource. A catalytic converter on a car, destroys vehicle emissions but imagine if we harvested them? It’s about changing the mindset. And we’re in the early stages of doing that, but it will take different industries and scientists to work together to succeed.
