New research involving the UK Centre for Ecology & Hydrology (UKCEH) has shown that action to reduce ammonia emissions would be a cost-effective way to improve air quality and health.

The study, published in the journal Science, estimated the global impact of nitrogen air pollution and also the potential economic benefits of implementing measures to reduce emissions.

Modelling by the researchers estimated the contribution of different nitrogen compounds to PM2.5 - fine particulate matter less than 2.5 micrometres in diameter that causes millions of premature deaths worldwide a year. Ammonia, emitted mainly from agriculture, and nitrogen oxides from transport and industry bond with other gases in the atmosphere to form PM2.5, which penetrates the lungs and bloodstream, thereby aggravating respiratory and heart conditions.

The international research team, which was led by Zhejiang University of China and included Professor Mark Sutton and Dr Massimo Vieno of UKCEH, found that, globally, nitrogen pollution overall contributed 39 per cent of PM2.5. This corresponded to around 23.3 million years of life lost in 2013 at an estimated cost, in terms of damage to health, of 420 billion US dollars. In the UK, nitrogen pollution contributed 59 per cent of PM2.5 and 194,000 years of life lost at a cost of 11 billion USD.

In their cost benefit analysis, the researchers estimated that the cost of reducing ammonia emissions was a tenth of the amount to eliminate an equivalent amount of nitrogen oxides. They also calculated that, on a global scale, every $1 spent reducing ammonia emissions would result in preventing $4 of health damage, and in the UK this ratio rose to 23:1.

Professor Sutton says: “Agriculture contributes more to PM2.5 than traffic but while much has been done to tackle nitrogen oxide pollution, little has been done globally to reduce ammonia emissions. Our study shows action on nitrogen air pollution must be a priority, and that taking measures to tackle ammonia emissions would be a relatively low-cost way of improving air quality and health.”

Around 80 per cent of nitrogen is wasted due to inefficient use and application – an estimated 200 million tonnes at a cost of 200 billion USD. More efficient fertilisers and better methods for applying them to land can reduce ammonia from cropland, while covering stored manure and injecting liquid manure into soil can limit emissions from livestock.

Fertiliser is also a source of nitrous oxide, a form of nitrogen that is a greenhouse gas that also depletes the ozone layer and is 300 times more powerful than carbon dioxide. Global warming also exacerbates ammonia emissions, which will therefore undermine efforts to improve air quality.

Professor Sutton explains: “The issues of nitrogen linked, and tackling nitrogen pollution has multiple benefits for air and water pollution, climate and the economy. Our study is therefore relevant to the current negotiations at COP26, as well as other international policymaking decisions on climate change and air quality.” 

The #Nitrogen4NetZero initiative was launched earlier this year by the International Nitrogen Management System (INMS), which is led by UKCEH, and countries in South Asia.

In a statement to world leaders attending COP26, the partners emphasised the need for sustainable nitrogen management as part of climate change mitigation and adaptation. They also highlighted the ambition, agreed by 15 countries and backed by the UN Environment Programme in the 2019 Colombo declaration, to cut nitrogen waste by half to 100 billion USD a year by 2030.

Paper information
Gu et al. 2021. Abating ammonia is more cost-effective than nitrogen oxides for mitigating PM2.5 air pollution. Science. DOI: 10.1126/science.abf8623