Research: SEI expert gives evidence at UK Parliament nitrogen inquiry
Posted on 19 February 2025
The UK House of Lords is investigating nitrogen pollution, a major environmental issue caused by human activities. SEI’s Kevin Hicks provided evidence at an inquiry, emphasizing the need for an integrated strategy to address nitrogen’s various sources and impacts. The inquiry aims to investigate the effect of nitrogen pollution and explore how the government can adopt a more holistic and strategic approach to nitrogen management.
The growing threat of nitrogen pollution
Nitrogen is a fundamental element of life on Earth, making up 78% of the air we breathe in its inert, harmless form. It must be fixed into reactive forms to be of use to plants and is a key component of fertilizers that support global food production. Nitrogen fixation occurs naturally via lighting, fires and biological nitrogen fixation, but human activity associated with fossil fuel combustion and synthetic fertilizer production has resulted in more than a doubling of the amount of reactive nitrogen circulating in the environment. Nitrogen becomes a potent pollutant when it is lost to the environment, leading to harmful consequences for human health, water quality, biodiversity, climate change, the ozone layer and soils.
For example, nitrogen contributes to air pollution through nitrogen oxide (NOx) emissions and the formation of fine particulate matter (PM2.5) and tropospheric ozone (O3) in the atmosphere, all of which pose serious health risks.
Hicks highlighted the findings of the 2024 Global Nitrous Oxide Assessment, which underscores how nitrous oxide emissions – mainly from fertilizer use in agriculture – are accelerating climate change in the long term and depleting the ozone layer. As a greenhouse gas, nitrous oxide (N₂O) is nearly 300 times more potent than carbon dioxide and remains in the atmosphere for over a century; it is also the most significant ozone-depleting substance today.
Nitrogen inquiry
Recognizing the urgency of this issue, the UK House of Lords Environment and Climate Change Committee, chaired by Baroness Sheehan, launched an inquiry to examine nitrogen’s environmental impact and explore innovative solutions.
On February 5, 2025, the committee held its first evidentiary meeting, featuring insights from leading experts. Among them was Kevin Hicks, Senior Research Fellow at SEI’s University of York Centre. He joined specialists from the Centre for Ecology and Hydrology and the Institute for European Environmental Policy to examine the impact of nitrogen pollution and explore potential mitigation strategies.
The need for a unified strategy
Despite the severity of the problem, nitrogen pollution is currently addressed through a patchwork of regulations. Policies tend to focus on specific sources – such as vehicle emissions, fertilizer use and industrial waste – without considering their extensive, interconnected effects.
Hicks warned that this fragmented approach could lead to “pollution swapping,” where tackling one form of nitrogen pollution inadvertently worsen another. For example, reducing ammonia emissions from agriculture without addressing nitrate runoff could shift pollution from air to water. He called for an integrated approach that treats nitrogen as a valuable resource with the potential to benefit human health, the economy and the environment as part of a circular economy
Recycling nitrogen, he argued, could lower dependence on energy-intensive synthetic fertilizer production, reduce the need for imports and create new economic opportunities. “We need a strategy that looks at the entire nitrogen cycle – from fertilizer production to combustion emissions and wastewater treatment – to take a more balanced and effective approach,” he told the committee.
Though nitrogen is invisible to the naked eye, its impact is impossible to ignore. Developing long-term strategies to curb nitrogen pollution while balancing environmental and economic goals is essential.
This session marked the first in a series of expert testimonies for the House of Lords inquiry – an important step toward tackling nitrogen pollution in the UK. The committee will continue gathering evidence from diverse experts, including scientists and civil society groups, to shape recommendations on how well government departments are working together on nitrogen policy and to determine if a more joined-up and long-term approach to nitrogen management is needed.
Learn more about the inquiry by watching the committee proceedings.
By Kevin Hicks and Jennifer Aghaji, Stockholm Environment Institute at York (SEI-Y).
Photo: Jennifer Aghaji / SEI.