Emissions of air pollutants in the UK – Non-methane volatile organic compounds (NMVOCs)

Question 1

1. What are NMVOCs and why are their emissions estimated?

Accepted Answer

Non-methane volatile organic compounds (NMVOCs) are a large group of organic compounds which differ widely in their chemical composition but can display similar behaviour in the atmosphere. NMVOCs are emitted to the air from a range of sources, including combustion, petrol vapour, solvents, air fresheners, cleaning products, and perfumes.

NMVOCs can have negative impacts on health and the environment. Firstly, NMVOCs can react with other air pollutants outdoors in the presence of sunlight (via ultraviolet radiation) to produce ground-level ozone. Ozone poses risks to health by triggering inflammation and asthma, but also causes damage to vegetation, including crops.

NMVOCs also pose a threat to health indoors. Although ozone is not typically formed indoors since most ultraviolet radiation is absorbed by glass, reactions between different NMVOCs and chemicals from combustion processes such as smoking, heating, cooking or candle burning can produce dangerous chemicals like formaldehyde. Formaldehyde is a human carcinogen but is also known to cause irritation to the eyes and upper airways at low concentrations. The NMVOC formaldehyde can also be emitted directly from furniture, finishes and building materials such as laminate flooring, kitchen cabinets and wood panels.

Finally, NMVOCs can also contribute to concentrations of airborne particulate matter which also has serious health implications (see the particulate matter section of this release for more information). Due to the adverse effects NMVOCs can cause, alongside the wide geographical spread and large variety of sources, the UK aims to identify and reduce NMVOC emissions where possible.

NMVOCs can be emitted both by natural processes (such as vegetation, soils, and lightning) and as a result of human activities (such as food and drink production and the use of solvents). The National Atmospheric Emissions Inventory (NAEI) and the statistical tables published as part of this release mostly covers NMVOC emissions from human activities, but there are a few exceptions included as memo items, such as forest fires. The information presented in this document only covers NMVOC emissions from human activities in the UK.

The revised Convention on Long Range Transboundary Air Pollution (CLRTAP) and National Emission Ceilings Regulations (2018) (NECR) requires the UK to reduce emissions of NMVOCs by 32 per cent compared to 2005 emissions by 2020 and in each subsequent year up to and including 2029 (and by 39 per cent compared to 2005 emissions by 2030).

Question 2

2. Trends in total annual emissions of NMVOCs in the UK, 1970 to 2022

Accepted Answer

Figure 10: Annual emissions of non-methane volatile organic compounds (NMVOCs) in the UK: 1970 - 2022

Notes:

‘ERC’ refers to our emission reduction commitment applicable between 2020 and 2029, as set out in the National Emission Ceilings Regulations (2018). This is applicable to the series ‘NMVOCs excluding emissions from agriculture’.
‘CLRTAP’ refers to our emission reduction commitment applicable from 2020 onwards, as set out in the Convention on Long Range Transboundary Air Pollution. This is applicable to the series ‘NMVOCs’.

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Emissions of NMVOCs decreased by 69 per cent since 1970, to 756 thousand tonnes in 2022. Emissions decreased by 5 per cent between 2021 and 2022.

NMVOC emissions reached the highest point in the time series in 1990 and then decreased on average by 5 per cent per year between 1990 and 2009. This was largely due to improvements to emissions standards for road transport and stricter limits applied to industrial processes. However, more recently annual changes have been much smaller, emissions decreased on average by 2 per cent per year since 2009. From 1990 to 2022, NMVOC emissions decreased by 73 per cent.

The NECR sets out our emission reduction commitments to maintain emissions below 764 thousand tonnes throughout 2020 to 2029 (excluding agricultural sources). The UK did meet the 32 per cent emission reduction commitment in 2022.

Question 3

3. Major emission sources for NMVOCs in the UK

Accepted Answer

Figure 11: UK annual emissions of NMVOCs by 2022 major emission source: 1990, 2005, 2021 and 2022

‘Other Industrial processes’ refers to the ‘industrial processes and product use’ sources that are not captured within the other sources in this figure.
‘Domestic solvents’ refers to the solvents in consumer products such as aerosols, detergents and fragrances. This includes the usage of fungicides and other agricultural chemicals.
‘Coating Applications’ refers to the use of solvents in industrial coatings (such as specialist finishes applied to vehicles, wood, metal and plastic products) and decorative paints.

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Domestic solvents were the largest source of NMVOC emissions in 2022, which has grown as a source over time along with population growth (this source contributed 22 per cent of total emissions in 2022 and has increased by 10 per cent since 1990). Emissions from this source peaked in 2020, largely due to increased hand sanitiser use throughout the COVID-19 pandemic, but have since fallen back to pre-pandemic levels. Most emissions from this source come from household products, cosmetics and toiletries, followed by emissions from vehicle screen wash.

Fugitive emissions (that is losses, leaks and other releases of gases) are associated with the extraction, refining and distribution of fossil fuels like oil and gas. Fugitive emissions of NMVOCs from these activities have reduced substantially (they decreased by 66 per cent since 2005), although in 2022 they still contributed 12 per cent of NMVOC emissions. The decline in coal mining and the production of oil, coupled with better emissions control, is responsible for the long-term decline in emissions from this source. The largest contributor towards fugitive emissions of NMVOC’s in 2022 was gas leakage from natural gas supply, followed by fugitive emissions from offshore oil loading and fugitive emissions from petrol refuelling at petrol stations.

Emissions from agriculture have increased by 11 per cent from 1990 to 2022 and contributed 17 per cent of NMVOC emissions in 2022. This has largely been driven by an increased use of manure-based fertilisers and growth in the rearing of chickens over this time period.

Emissions from food and beverages production have also increased over the long-term. Between 1990 and 2022 they increased by 44 per cent, from 82 thousand tonnes in 1990 to 118 thousand tonnes in 2022. The largest source of emissions of NMVOCs in this sector is Scotch whisky production (which contributed 11 per cent of NMVOC emissions in 2022) followed by the manufacture of animal feed (which contributed 2 per cent of NMVOC emissions in 2022), and bread baking (which contributed 1 per cent of NMVOC emissions in 2022). Consistent growth in emissions of NMVOCs is observed for Scotch whisky production since 1990, as NMVOC emissions from this source have increased by 98 per cent over this time period.

Emissions from the industrial use of solvents have reduced over time due to stricter emissions limits (particularly for coating applications, degreasing and chemicals production). Emissions of NMVOCs from these activities have fallen from 250 thousand tonnes for coating applications and 251 thousand tonnes for other industrial processes in 1990 to 55 thousand tonnes for coating applications and 65 thousand tonnes for other industrial processes in 2022.

Amongst other sources, road transport was a major source of NMVOCs in the early 1990s. In 1990 road transport contributed 33 per cent of emissions (916 thousand tonnes). Stricter emission standards mean road transport only contributed 4 per cent of emissions in 2022 (30 thousand tonnes).

Levels and trends in emissions from specific sources are available for the period 1990 to 2022 through the statistical tables that accompany this release.