Emissions of nitrogen oxides, NMVOC, sulphur dioxide and ammonia. 1990-2008*

Reduced NOx emissions, but much remains

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The emissions of nitrogen oxides (NO X ) and fugitive organic compounds (NMVOC) decreased from 2007 to 2008. For sulphur dioxide (SO 2 ) and ammonia (NH 3 ), there were only minor changes. See Emissions of nitrogen oxides, NMVOC, sulphur dioxide and ammonia . This article provides a more thorough description of the different gases and their effect as acidifying gases or ozone precursors. First, the emission development for the different gases is discussed and then follows an account of the total impact on the environment.

Emission ceiling 2010 according to the Gothenburg Protocol and status 1990 and 2008*. Tonnes (per cent)
Component Emissions 1990 Emissions 2008* Emission ceiling 2010 Necessary reduction 2008-2010
Nitrogen oxides (NO X )  207 795  178 608  156 000 22 600 tonnes (13 per cent)
Sulphur dioxide (SO 2 ) 52 198 20 239 22 000 Emission ceiling reached at the moment
NMVOC  299 893  170 660  195 000 Emission ceiling reached at the moment
Ammonia (NH 3 ) 20 377 22 573 23 000 Emission ceiling reached at the moment
Source:  Emission inventory from Statistics Norway and Norwegian Pollution Control Authority.

Some types of air pollution can be carried over long distances and thereby have consequences for countries other than where they are actually emitted. The Gothenburg Protocol is an international environmental agreement aimed at reducing the emissions of such gases. The agreement comprises many European countries together with USA and Canada. It covers substances that contribute to acidification, overfertilisation and creation of ground-level ozone. The table below shows the status for Norwegian emissions in 2008 compared with the agreement’s emission targets for 2010.

The Norwegian emissions of NO x in 2008 totalled approximately 179 000 tonnes. This is about 15 000 tonnes, or 8 per cent less than the preceding year. In order to meet the emission obligation in the Gothenburg Protocol for 2010 (156 000 tonnes) the emissions must be reduced by a further 22 600 tonnes. Accordingly, an annual reduction of almost the same size as the reduction from 2007 to 2008 is needed in 2009 and 2010. The NO x emissions varied somewhat in the period 1990-2008, but in 2008 they were 14 per cent lower than in 1990.

The decrease from 2007 is particularly due to less use of fuels such as auto diesel and marine diesel. In addition, renewal of the car fleet and strict exhaust requirements have led to emission reductions. Less flaring at the LNG installation (installation for receiving and processing natural gas) on Melkøya outside Hammerfest also contributes to the decrease in NO X emissions. Half of the emission reduction from 2007 to 2008 was due to domestic sea transport and fisheries. It is uncertain how much of the decrease can
be attributed to the NO x tax and the NO x agreement (see box on NO x reducing measures).

Nitrogen oxides (NO x ) are chemical compounds of nitrogen and oxygen that are created when the gases are exposed to high temperatures, for instance by combustion. NO x have an acidifying effect on soil and water, contribute to overfertilisation, damage materials and also contribute to the formation of ground-level ozone. One of the NO x compounds, nitrogen dioxide (NO 2 ), may also cause respiratory disorders. Car traffic is the source of large NO 2 emissions, and particularly on cold, quiet winter days the outdoor air in areas with much traffic can be exposed to concentrations of NO 2 that may damage health.

Nitrogen contributes to approximately 10 per cent of the acidification in most of Norway. In southern and south-western parts of the country, however, the share is 30-40 per cent. Emissions of sulphur have been reduced more rapidly than emissions of nitrogen, thus the relative importance of nitrogen as a source of pollution has increased.

One sixth of the total NO X emissions come from road traffic. Although the number of driven kilometres with motor vehicles has increased by more than 40 per cent from 1990, the emissions have been more than halved, due to exhaust restrictions for petrol vehicles. The share of petrol cars with catalytic converters is still rising, but the emission decrease is somewhat counteracted by a higher share of diesel vehicles among new cars. Diesel cars cause larger NO x emissions than petrol cars. Heavy diesel vehicles have also reduced the emissions as continually stricter exhaust restrictions have been introduced.

Today, half of the NO x emissions from road traffic come from heavy vehicles and one third from private cars. Petrol cars without catalytic converters amount to only about 5 per cent of the private cars’ traffic labour, but cause approximately 20 per cent of the private cars’ NO x emissions.

NMVOC emissions well below the obligation for 2010

The emissions of NMVOC (non-methane volatile organic compounds) totalled 171 000 tonnes in 2008. This is 14 per cent less than the year before and far below the obligation in the Gothenburg Protocol for 2010 (195 000 tonnes). Since 1990, the emissions have been reduced by 43 per cent. From the peak in 2001, the emissions have been reduced by 57 per cent.

A total of 85 per cent of the decrease from 2007 to 2008 is caused by lower emissions from the loading and storing of oil on the continental shelf. The reduction from 2001 is also mainly due to a decrease in these emissions. The reduction has been achieved since the Norwegian Pollution Control Authority imposed the use of technology that reduces the NMVOC emissions by limiting evaporation and recovering oil vapour. The emission decrease in 2008 is due to process measures on the production installations, lower emissions from offshore loading because less oil was loaded, reduced emissions from production and storing vessels and a production decrease of about 5 per cent.

NO x from ships

Measures to reduce the NO X emissions from ships have been introduced during recent years. Only measures that bring about reduced fuel use are reflected in the emission figures presented now. A project aiming to revise the emission factors for NO x from ships for the whole period from 1990 has been initiated. It is not known how large the effects of the results from this project on the present emission figures will be. Additionally, consumption figures for sea transport may be partly revised.

NMVOC is a collective term covering a number of different chemical compounds. When they react together with nitrogen oxides (NOx) influenced by sunlight, ozone is created. High levels of ozone near the ground can cause damage to health, vegetation and materials. NMVOC can also contain carcinogens.

Emissions from solvents have been comparatively stable in the period from 1990, at about 50 000 tonnes. In 2008, however, these emissions were, for the first time in this period, the most important source of Norwegian NMVOC emissions, due to the decrease in emissions from the loading of oil on the continental shelf.

NMVOC emissions from road traffic have been reduced by 70 per cent since 1990. There has been an ongoing decrease throughout the whole period, which also continued in 2008. This is due both to the exhaust restrictions for petrol cars, which were introduced in 1989, and a continually larger share of diesel cars, which cause considerably lower NMVOC emissions than petrol cars.

NOx reducing measures

In autumn 2006, the Norwegian Parliament passed a tax on emissions of NO x from 1 January 2007. In 2008, the tax amounted to NOK 15.39 per kg of NO x emitted. The tax covers ships, fishing vessels, air traffic and diesel railways, as well as engines, boilers and turbines in energy plants in the manufacturing industries. The tax comprises only large units. Large units are defined as units with a capacity higher than 10 MW for boilers and 750 kW (1020 hp) for propulsion engines. In addition, NO x tax is imposed on flaring offshore and on oil and gas installations on shore. The tax covers approximately 55 per cent of the total Norwegian NO x emissions. The tax is delimited geographically in accordance with the Gothenburg Protocol. This means, for example, that emissions from foreign sea and air transport are not covered.

Simultaneous with the passing of the tax, it was resolved that tax exemption can be granted to enterprises that enter into environmental agreements with the Government on NO x reducing measures. In January 2008, 14 major trade associations signed such an agreement with the Ministry of the Environment. The agreement covers the period 2008-2010, and entails an obligation to reduce NO x emissions by 30 000 tonnes. Enterprises that join the agreement must make payments to the Business Sector’s NO x Fund, which shall allocate grants to carry out cost-effective NO x measures. The payment is NOK 4 per kilo of NO x , but NOK 11 for oil extraction. Relevant measures can be the installation of purification equipment, improvement of combustion processes or transition to less polluting energy goods. The emission reduction is expected to mainly take place in 2010 and shall be fully accomplished in 2011. If less than 90 per cent of the emission obligation is fulfilled by the deadline, tax must be paid for the part of the emission reduction that has not been achieved.

SO 2 emissions at a stable, low level

Sulphur dioxide (SO 2 ) is a gas created by combustion of sulphurous matter, particularly oil and coal, and which also arises in a number of industrial processes. It has an acidifying effect on soil and water and damages materials. SO 2 may also cause respiratory disorders. However, this is not considered a problem in Norway today, due to low concentrations in outdoor air.

It is assumed that about 90 per cent of the sulphur downfall in Norway originates from other countries, particularly Great Britain, Germany and Poland. This has caused a strong acidification of many lakes in southern parts of Norway, with great consequences for many fish stocks. The emissions are also decreasing in the countries that contribute most to sulphur downfall in Norway, and these countries too seem to be able to fulfil their emission obligations.

The emissions of SO 2 totalled 20 200 tonnes in 2008, which is somewhat more than in 2007. The increase is mainly due to higher emissions from a ferroalloy producing plant. The SO 2 emissions seem to have settled at a level slightly below the target in the Gothenburg Protocol (22 000 tonnes). During recent decades there has been a pronounced reduction in Norwegian SO 2 emissions: In 2008 the emissions were more than 60 per cent lower than in 1990 and 85 per cent below the 1980 level. The decrease is due to less use of oil, reduced sulphur content in oil products, cleansing measures in manufacturing industries and plant shutdowns.

During the whole period from 1990, more than half of the SO 2 emissions have come from industrial processes, mainly from metal production. If stationary combustion also is included, manufacturing industries have been responsible for 70-80 per cent of the total Norwegian SO 2 emissions in this period. Next to manufacturing industries, domestic sea transport and fishing have the largest emissions; approximately 20 per cent of the total in recent years. However, this share has risen during the period from 1990.

Stationary combustion, in and outside the manufacturing industries, has caused about a quarter of the SO 2 emissions in the whole period from 1990, but the emissions have been more than halved. The reduction is caused both by less use of oil and lower sulphur content in oil products.

Emissions from road traffic have been reduced by more than 98 per cent from 1990, due to lower sulphur content in fuels. Only 0.3 per cent of the national SO 2 emissions are now caused by road traffic, which is one of the most important sources of emissions of CO 2 and NO x . In 1990, 6.3 per cent of the Norwegian SO 2 emissions came from road traffic, and in 1993 as much as 8.9 per cent.

Oil and gas activities, which also make a large contribution to emissions of CO 2 and NO x , are insignificant for SO 2 emissions, among other tings because natural gas contains very little sulphur.

Acidification of the environment is caused by inputs of acidifying substances with rain and snow or direct deposition of gases or particles on vegetation (dry deposition). Both of these processes are normally included in the definition of acid rain. Acid rain is caused mainly by emissions of sulphur dioxide (SO 2 ) and nitrogen oxides (NO x ) from the combustion of fossil fuels. In addition, ammonia (NH 3 ) and ammonium ions (NH 4 ) contribute to acidification through various chemical processes that take place in soil and water. Air pollutants are often transported for long distances, for example from central Europe or Britain, before ending up as acid rain in Norway. Many parts of Norway have lime-poor soils and sensitive vegetation, and the impact of acid rain is greater than in many other areas where deposition of acid components is higher. The damage has been particularly severe in Southern Norway, the southern parts of Western Norway, and Eastern Norway. Sør-Varanger municipality in Finnmark suffers the effects of acid rain from sources in Russia.

Acidification of soils results in leaching of nutrients and metals (especially aluminium). Freshwater organisms have suffered the most serious damage, and the most obvious effect has been the serious depletion of freshwater fish stocks in the southern half of Norway. In addition to its impact on the flora and fauna, acid rain results in corrosion damage to buildings and cultural monuments.

Sulphur dioxide acts only as an acidifying substance, but the problems related to releases of nitrogen compounds are more complicated. Nitrogen also has a fertilising effect and can result in changes in the species composition of the vegetation. Species that can make use of an extra nitrogen supply benefit at the expense of other species. Increased nitrogen supplies can lead to eutrophication in aquatic ecosystems. Nitrogen has an acidifying effect if inputs are larger than the amount the vegetation can absorb.

Norwegian authorities have entered into an agreement with the Federation of Norwegian Industries, in which the manufacturing industries assume the responsibility to reduce SO 2 emissions by up to 5 000 tonnes by 2010, compared to the 1999 emissions. The manufacturing industries are now introducing necessary emission reducing measures in order to fulfil their part of the agreement..

Ammonia emissions stable

Emissions of ammonia were unchanged from 2007 to 2008, at 22 600 tonnes. These emissions, which mainly stem from agriculture, have been at the same level for several years. Since 2001, the emissions have been just below the obligation in the Gothenburg Protocol (23 000 tonnes).

Acidifying substances

fig - 2009 - 05 - 19 - 05 - en ; Emissions of acidifying substances in Norway . 1 000 tonnes acid equivalents . 1990 - 2008 *

Aggregate emissions of acidifying substances, expressed as acid equivalents, amounted to 5 843 tonnes in 2008. NOX accounted for 66 per cent of the total and NH 3 and SO 2 for 23 and 11 per cent respectively. Emissions of acidifying substances were reduced by 5 per cent from 2007 to 2008, due to the large decrease in NO x emissions. The reduction amounts to 20 per cent from 1990 to 2008.

Ground-level ozone (O 3 ) is formed by oxidation of ozone precursors (CH 4 , CO, NO x and NMVOCs) in the presence of sunlight. Emissions of ozone precursors are regulated by the Gothenburg Protocol. The formation of ground-level ozone increases the risk of respiratory complaints and damages vegetation and materials. In Scandinavia the background level varies between 40 and 80 μg/m 3 and is generally highest in spring. The background level for ozone is much closer to the levels that affect health and vegetation than is the case for most other air pollutants. There are large variations in levels of ground-level ozone from year to year.

The ozone-forming potential of ozone precursors varies. A weighting factor is defined for each of these precursors according to how much ground-level ozone it forms during a specific period of time. These are known as TOFP (Tropospheric Ozone-Forming Potential) factors, and NMVOCs are used as the reference component.

Substance : TOFP factor :

NOx 1.22

NMVOC 1

CO 0.11

CH4 0.014

If the Norwegian emissions of ozone precursors are weighted with the TOFP factors and summed up to total TOFP emission, we see a 33 per cent decrease in the period 1990-2008.

Preliminary figures

The figures presented in this article are preliminary, but are relatively reliable. This particularly applies to total emission figures. The sales statistics for petroleum products, based on reports from the oil companies on sales of oil products to different consumer groups, forms the basis for calculating combustion emissions. Possible errors and insecurities in these statistics will have a direct effect on levels and trends in the emission statistics.

Documentation of the emission calculations

The Norwegian Emission Inventory 2008. Documentation of methodologies for estimating emissions of greenhouse gases and long-range transboundary air pollutants .


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