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Emissioner fra træfyrede brændeovne og -kedler 3 English SummaryBackground and objective Denmark has ratified the POP Protocol under the Geneva Convention on long range transboundary air pollution and must comply with the emission ceiling in the NEC Directive in 2010. During recent years, several information campaigns have been carried out on correct firing, and furthermore, a large number of old wood burning stoves and boilers are replaced annually by new and more environmentally acceptable units. During the last six months of 2008, a scrapping subsidy was introduced resulting in the replacement of many old boilers. In June 2008, the new “Statutory Order regulating air pollution from wood burners and boilers and certain other fixed energy-producing installations” came into force. Finally, a number of field and laboratory tests have been conducted in recent years in Denmark as well as in other Scandinavian countries with a view to gaining more and better knowledge of the emissions from wood stoves and boilers. A considerable part of the Danish emissions to the air, especially emissions of PAH, particulate matter (PM), dioxin, and NMVOC, comes from stoves and boilers, and with an increasing firewood consumption, the challenge of reducing the pollution grows. The objective of this project is to provide an updated inventory of the firewood consumption distributed among the existing stoves and boilers and to study and propose, if necessary, a revision of the respective emission factors. The results of the project will be used as a basis for updated projections of air emissions, the further efforts to reduce the pollution, and to support Denmark’s reporting of the development in order to meet international obligations. The study In order to provide an updated inventory of the firewood consumption in relation to technologies, chapter 4 gives a distribution of the firewood on technologies based on the Danish Energy Agency’s inventory of the firewood consumption and an analysis of the current mix of stove and boiler types. In addition to existing studies, a minor qualitative analysis is made in this project in which 15 chimney sweepers - chosen randomly in urban, country and summer house areas - have kindly shared their knowledge. The other part of the project is primarily a literature study of various studies of emission factors. Based on recent studies, measurements and analyses of emissions from stoves and boilers, an analysis is given in chapter 5 of the need for updating Denmark’s current emission factors particulate matter (PM), dioxin, NMVOC and PAH. Main conclusions Based on an analysis of the current mix of wood burning stoves and boilers from 2005, the development in this stock has been updated to a 2008 level through a chimney sweeper analysis, trade sales figures etc. It is estimated that the replacement of stoves during this period has been within the order of 5-8 % per year corresponding to a level of 25,000-40,000 per year. The number of uninstalled stoves per year is reported to be approx. the same as the number of new registrations which gives a constant total number of stoves. There seems to be no difference between urban and country areas, whereas the replacement rate seems to be lower in summer house areas. Design, trends and environmental considerations seem to weigh heavily as a motive to replace stoves in the urban areas. More stoves were replaced in 2006-2007 than in 2008 because of the financial crisis which has also had an effect on this trade. The replacement of wood boilers shows a level of 4-5 % per year, however with 2008 on a slightly higher level, especially because of the scrapping subsidy. Also here the analysis indicates that the total number is constant which means that old boilers are replaced by new ones. In this report is not done modelling on the number of wood pellet stoves as the emission can be determined precisely based on the sales figures for wood pellets. Therefore, the specific number of pellet stoves and boilers is less relevant.
* The Swan Label is an environmental labelling scheme for the Nordic Countries. It can be compared to the European Union’s Flower Label. The analysis based on interviews with chimney sweepers indicates increased environmental awareness and changed and improved firing habits among the users. It is proposed changing the Danish categorization of stoves and boilers to more specific names related to the standards to be observed. All new studies and tests show that the firing method is the factor dominating the quantity of PM emissions from stoves and boilers. This is also the case for old stoves, boilers and fireplaces. Based on the increased awareness of the environment and firing methods and the technology improvement realized in general, it is proposed reducing the current emission factor for particles from stoves so that it will be at the same level as EMEP/EEA Emission Inventory Guidebook, 2009, in the following called the Guidebook. Furthermore, it is proposed reducing the particle emission factor for old boilers to a level which is between the current level and the Guidebook. As to emission factors for dioxin, there are only few recent measurement schemes, and they do not show a clear picture of the dioxin emission from the individual technologies. Two adjustments are suggested to align the emission factors with the recommendations of the Guidebook. There are no recent Danish or foreign studies indicating that it should be necessary to propose changes in the emission factors for PAH for stoves. Recent Danish measurements on boilers show a very high level for PAH emissions from old boilers. As there has been no distinction between emissions from old boilers with or without an accumulation tank so far, it is proposed increasing the emission factor for old boilers without accumulator tank. It is proposed to increase the emission factors for new boilers as well. All recent measurements and studies concerning emissions of NMVOC show a clearly decreasing level for modern stoves compared to old stoves. It is proposed reducing the Danish emission factor for DS labelled stoves from 1990-2005 to a somewhat lower level. On the other hand, it is proposed increasing the current level of the emission factor for old boilers without an accumulator tank as the current emission factors do not distinguish between boilers with and without an accumulator tank, and Swedish studies show a considerably higher emission level for boilers without an accumulator tank. Project results The total consumption of wood and wood pellets is given in the Energy Statistics from the Danish Energy Agency. According to the statistics, there has been an increase in the consumption of wood in the period 2005-2008 of 39 % and an increase in the consumption of pellets of approx. 23 %. Based on the results of the study among the chimney, the consumption of firewood is distributed on technologies in the table below.
The other part of the study consists of a literature study on recent studies and measurements that might motivate a revision of DMU’s current emission factors. The table below shows the proposals for new emission factors given in this project. Click here to see: Table 4: Proposal for new emission factors.
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