Written evidence submission from the Environmental Investigation Agency (NIT0006)

House of Lords’ Environment and Climate Change Committee: Written call for evidence on nitrogen

Submission by the Environmental Investigation Agency (EIA UK)

The Environmental Investigation Agency (EIA) is a UK-based non-profit organisation investigating and campaigning against environmental crime and abuse. EIA’s climate programme seeks to meet the climate challenge through rapid, sustained reductions in emissions of all greenhouse gases, including nitrous oxide, methane and fluorinated gases, by developing ambitious national, regional, global and sectoral obligations, reinforced by strong governance frameworks.

EIA welcomes the opportunity to respond to the call for evidence of the Environment and Climate Committee of the House of Lords.

What are the main sources of nitrogen pollution in the UK? How and why have these changed over time?

Throughout this submission, EIA’s response will focus on nitrous oxide (N2O), a form of reactive nitrogen which is both a powerful greenhouse gas (GWP100 273)[i] and the most prevalent ozone depleting substance in the world today.[1] In 2022, the UK emitted approximately 18.5 million CO2-equivalent tonnes (tCO2-eq) of N2O.[2]

Agriculture is the main source of anthropogenic N2O emissions in the UK, accounting for around 70 per cent of the annual total.[3] The single most significant driver of these emissions is the application of synthetic nitrogen fertilisers to cropland, however manure management and field burning also contribute. Fossil fuel- and biomass-based energy, transport and wastewater are also significant sources of N2O in the UK, accounting for roughly 30 per cent of annual emissions collectively.[4]

The UK’s agricultural N2O emissions declined slightly during the 2000s and 2010s, as implementation of the EU Nitrates Directive led to a reduction in the use of synthetic fertilisers, however this gain was partially offset an increase in the number of large-scale, intensive livestock farming units (20 per cent since 2016).[5] In previous decades, industrial emissions from nitric and adipic acid production were also significant sources of N2O in the UK.[6] This is no longer the case, as abatement technologies now operate in all UK nitric acid facilities, and domestic production of adipic acid ceased in 2009.

How could nitrogen pollution be mitigated from relevant sectors, how effective are these approaches, and are there any trade-offs?

The UNEP/FAO 2024 Global N2O Assessment projects that global implementation of existing technologies and best practice could mitigate 22 per cent of N2O emissions by 2050 (relative to 2020). Factoring in societal changes (most significantly a reduction in meat and dairy consumption), the Assessment projects this could be increased to 44 per cent.[7]

Although some technical reductions are already being implemented in the UK (such as abatement of emissions from nitric acid production), there are many measures which are not yet employed, or which could be improved. These include:[8]

Agriculture (arable)[9]

• Nitrogen testing of soil and plants, to facilitate precision farming practices
• Reducing fertiliser application, as appropriate
• Practising split-application using controlled-release fertilisers, as appropriate
• Applying urease and nitrification inhibitors, as appropriate
• Integrating nitrogen-fixing crops into rotations
• Reducing tillage and planting cover crops
• Creating buffer strips between agricultural fields and wetlands/waterways

Agriculture (livestock)[10]

• Implementing rotational grazing of fields
• Separating solid manure and slurry
• Storing manure under dry conditions and implementing rapid drying practices
• Processing livestock waste through anaerobic digestion

Wastewater[11]

• Separating commercial and residential wastewater
• Investing in nitrogen recovery infrastructure

The trade-offs associated with these technical reductions vary, and their applicability is not universal. The common ‘trade-off’ though, is the cost of implementation and the requirement for supporting infrastructure to be developed.

Balancing this, there are significant benefits beyond the direct reduction of N2O emissions. For example, separation of water coming from commercial and residential sources has the potential to mitigate 60 per cent of N2O emissions from wastewater treatment, but it can also facilitate the recovery of nutrients that can be used for agricultural purposes and thus offset the need for energy-intensive fertiliser production.[12]

What future developments could further increase nitrogen pollution, and how could those risks be reduced?

There are several emerging decarbonisation measures being pursued globally that could lead to significant increases in emissions of N2O. Three examples are outlined below:

Ammonia as a fuel

Interest in using ammonia as an alternative fuel has grown in recent years, especially in the context of international shipping.[13] Ammonia has a high energy density, can be stored as a liquid and does not contain carbon, so does not emit CO2 when burned. Unfortunately, combustion of ammonia can emit significant quantities of N2O–harming the climate and ozone layer–and NOx–worsening air quality.[14] Several studies have projected that, due to the potential volumes of N2O emitted during combustion, the use of ammonia as a shipping fuel could have an even greater climate impact than the use of traditional fossil fuels.[15]

Bioenergy systems

The wider deployment of bioenergy systems will increase N2O emissions if these systems rely heavily on feedstock crops produced with large amounts of fertiliser. Over the last two decades studies have consistently demonstrated that N2O emissions associated with the production of bioenergy crops like maize and rapeseed can significantly offset the climate benefit achieved by replacing fossil fuels.[16] Agricultural mitigation measures can reduce the N2O emissions associated with bioenergy crop production, but there are also alternative feedstock crops, notably perennial crops, which require less fertiliser and which produce less waste and residues.[17]

Soil carbon sequestration

Estimates that agricultural soils could sequester over a billion tonnes of carbon annually have encouraged a rapid expansion of market and policy incentives to promote the practice.[18] As research into this topic has developed however, evidence has come to light suggesting that soil carbon sequestration can trigger heightened N2O emissions from soil.[19]  This would mean that the climate benefits achieved through a widespread increase in soil carbon sequestration would be less than previously suggested, particularly if no steps to address soil N2O emissions are taken.[20]

What are the ecological impacts of nitrogen pollution in the UK and what implications do these have for national environmental and net zero targets?

N2O is a potent greenhouse gas and an ozone depleting substance. Remaining in the atmosphere for around 115 years, N2O accumulates, traps heat and forces global temperatures upwards, whilst simultaneously depleting the stratospheric ozone layer and exposing the planet’s surface to greater levels of harmful UV radiation.[21]

The Climate Change Committee’s Seventh Carbon Budget recommends that the UK Government commit to more than halving N2O emissions by 2050 (a 53 per cent reduction, relative to 2008 levels).[22] This level of reduction, which the Committee believes is necessary for the UK to meet its net zero goals, can only be achieved through concerted mitigation of emissions from the agricultural sector.[23]

Globally, anthropogenic N2O emissions are outpacing all previous projections, having already increased by 40 per cent since 1980.[24] If N2O emissions continue to increase at their current rate, there is no plausible pathway to limiting global warming to 1.5°C, and the ozone layer will be depleted to its lowest levels this century.[25]

This global picture is important, as domestically, the UK is heavily reliant on N2O-emitting supply chains, even in sectors where domestic emissions are effectively mitigated. This includes nitric and adipic acid production. In sectors such as these, where UK policy has proven effective in N2O mitigation, the UK should seek to leverage its position to encourage international adoption of best-practice mitigation measures globally.[ii]

What are the public health impacts of nitrogen pollution and how are these accounted for in current government plans and targets?

As noted above, N₂O emissions contribute to stratospheric ozone depletion, weakening the ozone layer and allowing more harmful UV radiation to reach the Earth's surface. This increases the risk of skin cancer and cataracts, even at the UK’s Northern latitude.

If the current N2O emissions trend continues, cases of squamous cell carcinoma within the UK’s latitudinal band are projected to increase by roughly 2.5 per cent this century.[26] In addition, cases of basal cell carcinoma are projected to increase by almost 1.5 per cent and cases of cutaneous malignant melanoma by around 0.5 per cent.[27] In Southern latitudes, skin cancer rates are projected to increase by as much as 10 per cent.[28]

Reducing N2O emissions would also cut emissions of harmful co-pollutants, including ammonia and NOx. This would result in significant air quality improvements and public health benefits, as these co-pollutants contribute to the formation of fine particulate matter and ground-level ozone. By 2050, the Global N2O Assessment projects that the indirect air quality benefits resulting from N2O mitigation could prevent around 20 million premature deaths worldwide, including four million within the next decade.[29]

How effective is existing policy at regulating and reducing nitrogen pollution? How could they be improved? Are there gaps?

To date, the UK has had limited success in reducing N₂O emissions from agriculture.[30] Where targets do exist to reduce agricultural N2O emissions, most are voluntary and lack enforcement mechanisms, leading to inconsistent progress.[31] The nitrogen vulnerable zone (NVZ) system, derived from EU regulations, imposes some limits on nitrogen fertiliser application, but standards are not currently set at an ambitious level and so its impact on reducing emissions has been minimal.

To improve domestic regulation and better reduce agricultural N₂O emissions, the UK should adopt a more integrated and enforceable nitrogen management strategy. Strengthening existing regulations by mandating best practices—including targeted fertiliser reductions in high-emission areas—could significantly lower emissions. Additionally, shifting from voluntary measures to mandatory requirements, and supporting them with financial incentives, would encourage broader adoption of sustainable nitrogen management practices.

On the international side, as co-chair of the Climate and Clean Air Coalition (CCAC), the UK Government should recognise that it is uniquely positioned to lead global efforts to reduce N₂O emissions. Given its strong climate commitments and history of driving international climate action, the UK has a chance to spearhead policies promoting sustainable agricultural practices, industrial innovation and improved waste management to curb N₂O emissions.

By leveraging its leadership within the CCAC and focussing on multilateral forums with a track record of increasing their scope and ambition (notably the Montreal Protocol), the UK has an opportunity to galvanise international cooperation, set ambitious reduction targets and support developing nations in adopting cleaner technologies. The UK’s negotiating teams should be given a clear mandate by the Government to pursue this goal, guaranteeing a consistency of message across multilateral forums.

What are the pros and cons of taking a more holistic approach to nitrogen management in policy, and what opportunities to do so exist?

Taking a holistic approach to nitrogen management offers multiple benefits that address a range of environmental, economic and national security concerns.

From a climate perspective, reducing N₂O emissions is crucial, since it is a potent greenhouse gas with a long atmospheric lifespan. Additionally, N₂O contributes to stratospheric ozone depletion, which increases exposure to harmful UV radiation. As previously noted, addressing nitrogen pollution holistically would also improve air quality by reducing emissions of ammonia and nitrogen oxides, both linked to respiratory disease and premature death.

Economically, better nitrogen management can improve agricultural efficiency by reducing and optimising fertiliser use, reducing costs for farmers and ensuring less wastage of valuable nutrient resources.[32] This approach also enhances food security by ensuring sustainable agricultural practices that maintain long-term soil health. From a national security perspective, reducing reliance on synthetic fertilisers—often produced using imported energy sources—can also increase resilience to supply chain disruptions and market fluctuations​.

Opportunities to implement holistic nitrogen management include stricter agricultural policies, investment in precision farming technologies and financial incentives for sustainable land use practices. A National Action Plan (NAP) for nitrogen–addressing nitrogen pollution across the full nitrogen cycle–would help align agricultural policies with environmental and climate goals​. The UK has already appointed National Focal Points to the UNEP Nitrogen Working Group tasked with assisting countries in developing such plans and should now begin the development of its own NAP.[33]

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