Clean Air – Emission Sectors

The session focused on three main emissions sectors - agriculture, residential wood-burning, and shipping. For these sectors, past emission reductions have generally been slower than in many other sectors, and future emission projections indicate similar patterns. Regarding agricultural emissions, the link to food and dietary issues was stressed in the discussions, as well as links to other policy initiatives that directly or indirectly will impact agricultural livestock production, a key emission source for ammonia and methane. Emissions from residential wood-burning is responsible for a growing share of PM-pollution in cities, but significant reductions could take place by changing to other types of heating systems. For shipping, there is an urgent need to investigate potential negative impacts of new/alternative fuels and propulsion systems, but there are also great opportunities to improve current legislation (e.g. the IMO NOx-standards) and to expand the emission control areas in Europe and in the Arctic.

Agriculture

Livestock production is the main source of ammonia emissions, and also a big source of methane emissions. Halving ammonia emissions in Europe is possible, but it would require dietary changes.

Abstracts of presentations

Rasmus Einarsson, Swedish University of Agricultural Sciences (SLU)

Nitrogen emitted from agriculture as ammonia, nitrate, and nitrous oxide affects air quality, biodiversity, and climate. An integrated perspective of these emissions is needed as they are causally connected and mitigation of one emission can have co-benefits or trade-offs with other emissions.

Agricultural emissions of ammonia and greenhouse gases share several common drivers. Broadly speaking, countries with high ammonia emissions tend to have higher agricultural greenhouse gas emissions. Livestock production, including feed production, dominates agricultural emissions of ammonia and greenhouse gas emissions.

Food systems research shows that substantial mitigation of these emissions is possible. Technical and management improvements may enable emission reductions around 20-40% at current production volumes, given concentrated efforts in research and innovation, and with sustained policy support. To reach emission reductions around 40% or more, reduced primary production appears necessary. Strongly reduced primary production is possible without decreasing supply of food calories, protein, etc., if human diets shift towards more plant-based food and if non-food demand (e.g., biofuels and fibre) does not expand too far.

Among environmentally inclined food-systems researchers, a common sentiment is that basically "everything is known", in the sense that research has already quantified the technical, management, and consumption factors most important to mitigate emissions. The major gap, according to this sentiment, is not a knowledge gap, but an action gap.

The policies and agreements touching on these emissions are mostly focused on specific pollutants. They vary from specific and binding (e.g., EU NECD and EU Effort Sharing Regulation (ESR)) to more general and/or with weak enforcement (e.g., UN CBD, the UNFCCC Paris Agreement, and the Global Methane Pledge).

As mentioned, these different emissions share common drivers (i.e., the intensity and scale of agricultural primary production), but the most stringent policies tend to focus on individual pollutants. It is therefore a common concern – at least among researchers – that policy is not sufficiently joined-up and systems-oriented, and that cost-benefit analyses of mitigation do not capture all the relevant benefits.

During this workshop, it would be interesting to reflect on the sufficiency of available cost-benefit analyses, available scientific knowledge and data, and the existing policy types/policy frameworks to address the challenges associated with agricultural emissions of nitrogen and greenhouse gases. More specifically, the following questions should be addressed:

Are there major gaps in scientific knowledge or data limiting progress on air quality, biodiversity, climate?
Imagine a total cost-benefit assessment of mitigation options for agricultural emissions. Would authorities and governments use it?
Are pollutant-specific policies sufficient to address different types of nitrogen pollution, or is a more joined-up policy approach needed?

Short overview of discussions

The discussions focused mainly around how to better utilize the advice given by existing knowledge on agricultural emission control, and a main theme was how to convert knowledge to action. In addition, the workshop discussed whether Nordic cooperation could facilitate production of Nordic guideline documents to reduce emissions, improve coordination between policy domains affecting agricultural emissions, and whether it is desirable to drive a policy process towards mandating national nitrogen budgets in a revised NEC Directive.

Recommendations

Initiatives & Projects

The Nordic cooperation on air quality should aim to:

Strengthen nitrogen policies by including structural measures such as dietary change (for example reduced meat consumption). It is clear that the ammonia emission reductions needed to protect ecosystems and health, cannot be achieved by solely technical abatement measures. Nordic countries have good knowledge about and experience of nitrogen budgets. These could be further advanced and also spread to other countries. More Nordic research on future dietary needs and options and their role in reducing nitrogen emissions could be promoted. In this context, also climate aspects should also be taken into account.

Develop and improve knowledge sharing. Within the Nordic, there is a need to share knowledge and experiences on agricultural emission abatement measures, for example regarding the acidification of slurry. Such activities could also provide an opportunity to spread knowledge also to countries outside the Nordic to support further emission reductions.

Ensuring the application of integrated approaches to nitrogen management. These could focus on co-benefits to climate, water and biodiversity, both regarding specific measures and more general policies.

Residential heating

Heating residential buildings by burning solid fuels is the predominant source of several air pollutants in the EU. According to the EEA, the sector is responsible for 58% of PM2.5, 37% of black carbon, and 85% of benzo(a)pyrene (BaP) emitted in the EU. The majority of these emissions come from small wood-burning appliances.

Existing EU legislation, i.e. the Ecodesign Directive, will only deliver limited emission reductions over the next 5-10 years, meaning that additional (alternative) measures are needed.

Presentation abstract

Niko Karvosenoja, Finnish Environment Institute (SYKE)

Residential wood combustion (RWC) is the biggest source of PM_2.5 in all the continental Nordic countries: Finland, Sweden, Denmark and Norway (Paunu et al. 2022). The emissions are mainly caused by incomplete combustion in stoves that are relatively simple in structure and do not have advanced combustion control or flue gas aftertreatment systems (in contrast to other modern day combustion sources such as power plants, transport vehicles etc.). The amount of incomplete combustion depends – besides the stove structure and combustion technology – to a large extent on the combustion skills and habits of the stove user.

The only significant legislative measure in place to mitigate RWC emissions at the moment is the Ecodesign directive for solid fuel room heaters, which defines the emissions performance of new stoves and boilers that can be sold on the market. In the coming decades, the emissions are expected to decrease only slightly due to the slow turnover of stove stock. Correspondingly, RWC will remain the biggest source sector of PM_2.5emissions, with even a higher share of total emissions than today.

Although wood use per household is typically highest in rural areas, stoves are common also in relatively densely populated suburban detached house areas of Nordic cities, where the emissions cause considerable population exposure and potentially negative health impacts. Therefore, mitigation of emissions would be beneficial to direct towards urban areas so that benefits like improved public health can be achieved.

In a technical sense, there is a considerable potential to mitigate emissions from RWC by:

Improving combustion technologies of stoves and small boilers in use so that there will be less incomplete combustion and thus less emissions.
Reducing the amount of incomplete combustion by sharing information about proper use of stoves.
Cleaning the flue gases after the combustion by, e.g., catalytic methods or particle filters on chimneys.
Restricting the use of stoves.

The Ecodesign directive aims to improve stove technologies. However, it does not bring such strict requirements to stove manufacturers that it would drastically change the technologies used. Furthermore, it regulates only new appliances on the market. Stoves and boilers are often long lived, i.e. the turnover of appliance stock is slow, and the emissions from the stock decrease slowly. There have been attempts to accelerate the pace of the modernization by e.g. financial support or demands to purchase a new stove when moving to a new address. According to a Finnish survey and modelling study, financial support for new stove purchases does not appear to be effective policy. It is not a cost-efficient way to reduce emissions, nor a cost-effective way to improve public health (manuscript in preparation). This is supported by the results from a Norwegian study (Lopez-Aparicio & Grythe 2020). Sauna stoves, not covered by the Ecodesign directive now, are in the process to be added to the directive in the future. This could potentially reduce RWC emissions in Finland, depending on the requirements in the future legislation.

Information campaigns about proper combustion practices to reduce emissions have been carried out regularly in several Nordic cities. These have been shown to be a cost-efficient and immediate measure, although efficacy and permanence of the change are uncertain (Savolahti et al. 2016).

Aftertreatment of flue gases in RWC is not commonly used anywhere in the Nordic countries. There are several technologies in development or on the market (e.g. www.tassuesp.com, www.noeton.fi). However, the characteristics of RWC flue gases with discontinuous and variable composition and high amounts of organics make the removal challenging, and there are issues of price and need for maintenance of the appliances, which do not make the purchase tempting for stove users. It is not foreseeable that these technologies will become mainstream, unless technology- or emission-specific regulations are introduced and enforced.

There have been isolated cases of restricting RWC at certain times or technologies, e.g. ban on the use of old stoves in Bergen, Norway. As more wide-ranging mitigation efforts, bans or other prohibitive measures might be politically challenging to implement due to foreseeable resistance from the citizens. A “softer” option to try to mitigate RWC could be information sharing about the negative impacts of wood smokes on vulnerable people in the neighbourhood, e.g. targeted to urban areas during winter inversions.

Additional factors to take into consideration when assessing the feasibility and applicability of various measures to mitigate RWC emissions:

Stove technologies, use types and geographical locations vary a lot. Considerable amounts of stoves are used only occasionally and/or in sparsely populated areas. It is important to avoid measures that would heavily impact citizens or targets that are not causing considerable negative impacts.
There are differences in stoves and other characteristics between the Nordic countries, which are important to consider when, e.g., assessing common Nordic mitigation measures. For instance, radiative iron stoves, typical especially in Norway and Denmark, are lighter and easier to replace with new stoves than masonry heaters which is the most common stove type in Finland.
RWC is important from an energy security point of view. Stoves are the only heat source that does not require electricity. Power cuts are quite common, and especially in rural areas they can sometimes last tens of hours. This is important to keep in mind if considering banning stoves.

Short overview of discussions

The discussions on how Nordic cooperation can reduce emissions from residential heating circled mainly around which policy instruments that can be effective as well as cost-effective. The policy instruments discussed included potential establishment of (temporal) bans on wood burning in urban areas, faster implementation of - or stricter rules for - Ecodesign stoves in Nordic countries, as well as experiences from information on clean burning.

Recommendations

Initiatives & Projects

The Nordic cooperation on air quality should aim to:

Clarify opportunities and challenges with (temporal) bans on residential wood-burning in cities. To achieve satisfactory air pollution levels in cities, residential wood-burning in cities needs to be stopped, or completely new zero- or near-zero emission technologies for small-scale combustion developed. In cities, alternative heating options, such as district heating or various types of heat-pumps are readily available. There are several Nordic and European examples of local temporal and/or conditional bans. A Nordic project could investigate options for various measures, including bans, local regulations, and information campaigns promoting voluntary actions.

Promote Nordic information-sharing on tried and tested ways to reduce emissions from residential wood-burning.

Improve the knowledge on regional and time-dependent factors affecting health effects from residential wood combustion. Just as discussed during the session Clean Air – Cities and Societies, improved scientific understanding of effects from RWC would enable better policy advice from science. One issue that needs better clarification includes exposure-response functions for exposure periods shorter than one year but longer than a couple of days. Given that RWC in the Nordics is mainly an autumn/winter activity, the use of annual average ERF can lead to estimation errors in impact assessments. Another issue that needs clarification, or at least clear recognition, is the differences between urban and rural regions with respect to health effects, energy security, etc.

Clarify to what extent residential wood combustion affects BaP emissions. Even if Nordic PM_2.5 concentrations are relatively close to WHO guideline values and Nordic Environmental Quality Objectives, the same cannot be said for BaP. RWC is a key source also for BaP, and it is therefore important to increase the knowledge and attention to BaP emissions from RWC and how much these can be reduced through emission control measures.

Shipping

As shipping largely is an international business, it is logical to try and bring about global agreements for control of its air pollutant emissions, and since the early 1990s such work has been ongoing within the Marine Environment Protection Committee (MEPC) of the UN International Maritime Organization (IMO). Here, Nordic countries have been front-runners by proposing and establishing Emission Control Areas in the Baltic Sea and the North Sea through HELCOM and OSPAR with strong Nordic voice in both conventions.

While there is an EU-directive regulating the sulphur content of marine fuels, there are currently no EU standards for NOx or PM emissions from sea-going ships, although such standards exist for inland waterway vessels. NOx-emissions from international shipping are regulated through the IMO’s NOx technical code which defines NOx emission standards for vessels according to their key-lay date. The Baltic Sea, the North Sea and the English Channel have been designated as Emission Control Areas, with mandatory Tier III NOx-standard for all new ships built from 2021.

As regards national initiatives to cut air pollution from shipping, Nordic countries have shown leadership by, for example, introducing and applying economic instruments (e.g. the Norwegian NOx-tax and the Swedish environmentally differentiated port and fairway dues) and onshore power.

Abstracts of presentations

Jana Moldanova, IVL Swedish Environmental Research Institute

Despite decades of focus on reducing air pollutants from the shipping sector, significant challenges remain, especially with the addition of greenhouse gas reduction targets. Recent regulations have reduced sulphur oxide (SOx) emissions, particularly in Sulphur Emission Control Areas (SECAs). But outside these zones, such as in the Mediterranean and Atlantic, potential for further reductions remains. Parts of this potential will be fulfilled through the designation of the Mediterranean Sea as a SECA by 2025. However, using high-sulphur fuel with Exhaust Gas Cleaning Systems (EGCS, i.e. scrubbers) has introduced new environmental concerns. Scrubbers emit metals and other contaminants into the sea, posing an apparent risk of having serious impact on populations of key species of marine food webs. Further, scrubbers imply higher concentrations of PM_2.5 in ambient air compared to mitigation of SOx emissions through low-sulphur fuels. A study from the EMERGE project showed a 30% increase in PM_2.5-related health effects due to high scrubber use compared to scenarios with alternative fuels.

With respect to nitrogen oxides (NOx), the shipping sector's contribution has increased, and in 2020 ship NOx emissions in European seas was equal to around 50% of total EU land-based emissions. Despite the introduction of Nitrogen Emission Control Areas (NECAs) in the Baltic and North Seas in 2021, NOx emissions remain high due to the long lifetime of ships. In addition, underperformance of both Tier II and new Tier III vessels, especially at low engine loads, has been observed and due to these two facts, high NOx emissions from shipping risk continuing for a long time. Projections suggest that NOx emissions will significantly decrease by 2040 in NECA regions. However, non-compliance could hinder this progress, leading to 50% higher emissions and contributions to ambient NO₂ levels compared to the compliant scenario. Ozone formation from shipping emissions is particularly problematic in the Mediterranean, where conditions favour ozone production. Implementation of Mediterranean NECAs could reduce shipping's impact on ozone, but non-compliance could offset these gains.

Liquefied natural gas (LNG) is being promoted as a cleaner fuel option with a 100% increase in use between 2018 and 2022. However, LNG, particularly from 4-stroke engines, emits more methane than previously estimated, especially under low-load conditions. Being a potent greenhouse gas, these emissions have significant impact on climate.

The greatest challenge for shipping is decarbonization. The IMO aims for net-zero greenhouse gas (GHG) emissions by 2050, with interim targets for 2030. Promising low-carbon fuels, like ammonia, methanol, and hydrogen, come with new risks. For example, ammonia poses toxicity risks, its slip would contribute to PM formation and all alternative fuels have the potential to produce emerging pollutants, such as aldehydes, amines and nitro-PAHs, which requires further research.

Short overview of discussions

The fact that NOx emissions from ships in real-life driving conditions are higher than the emission standards result in higher health and environmental impacts, but also has add-on effects on policy analyses because emission inventories assume compliance with emission standards. Consequently, there is an urgent need to improve legislation.

New, so-called low-carbon shipping fuels and other GHG abatement measures for ships need to be scrutinised by full life-cycle assessments, to ensure that they bring real GHG-reductions and that they do not result in increased pollutant emissions either to the air or to the marine environment.

Recommendations

Initiatives & Projects

The Nordic cooperation on air quality should aim to:

Promote Nordic collaboration on alternative fuels and propulsion systems. Increased knowledge about potential negative well-to-wake impacts of alternative (zero- or low-GHG) fuels and propulsion systems are urgently needed, in order to avoid (yet unforeseen) environmental damage and sunk investments.

Provide Nordic leadership on ship emissions abatement. The Nordic countries have long shipping experience, academia, many ports, shipping companies, emission control manufacturers, etc. They have also been frontrunners for several “cleaner shipping” initiatives (e.g. ECAs, economic instruments, onshore power, alternative fuels and propulsion systems). Consequently, the NCM should promote Nordic cooperation to further this leadership.

Support the expansion of Emission Control Areas to all sea areas around Europe. Despite the effect of existing Emission Control Areas, shipping emissions still cause air pollution problems in Europe. Through an expansion of the ECAs, shipping emissions can be reduced. This would benefit most countries in Europe as well as reducing the input of BC to the Arctic.

Support a revision of the IMO’s NOx standards for ships. A fast introduction of revised NOx standards is needed to ensure that ships certified to the Tier II and Tier III standards perform according to the standards, not only at the time of certification but also in real-world driving. Ship emissions contribute significantly to nitrogen deposition in Nordic countries, and also to elevated NO₂-levels in Nordic port cities and coastal areas.