District Heating and the Environment

Urban air quality

The local pollution problem of high contents of dust, sulphur dioxide (SO2, and nitrogen oxides (NOx) in urban areas was among the first pollution problems to be identified. District heating improved the urban air quality in many Swedish towns during the 60's and 70's by the fact that local heat boilers were replaced and that the high chimney policy for district heat generation plants was used.

The introduction of The Sulphur Act in 1969, containing limitations of the sulphur content in fuel oil , also lowered the content of sulphur dioxide in the urban air. The great step was taken in 1977, when the maximum permissible content of sulphur in heavy fuel oil was reduced to 1 %.

Nowadays, mainly nitrogen oxide emissions f rom vehicles influence the urban air quality. District heating has substantially reduced the influence from heating on the urban air quality in Swedish towns. However, this fact is not new: A. E. Margolis wrote about this positive connection between district heating and urban air quality as early as 1940 (Margolis 1940).

Acidification

In Sweden, the regional pollution problem of acidification is a major problem. The Swedish soil can not neutralize the actual sulphur deposition due to acid rain, since the content of lime in the soil is low. However, 90 % of the sulphur deposition in Sweden comes from sources outside Sweden. Therefore, reduction of sulphur dioxide emissions from Swedish sources has a minor impact on the sulphur deposition in Sweden. Only reduction of sources outside Sweden will efficiently reduce the acidification in Sweden.

However, the fact described above is no excuse for not reducing the emissions of sulphur dioxide in Sweden. Therefore, the Swedish guidelines have been made more stringent during the 80's, and further lower limits will be introduced during the 90's. Several de-SOx-units have also been installed in coal-fired district heat generation plants during the 80's in order to fulfil the guidelines for sulphur emissions.

A new driving force for reducing sulphur dioxide emissions is the sulphur tax of 30 SEK per kg sulphur in the fuels peat, coal and oil. This tax was introduced on January 1, 1991.

Nitrogen oxides also contribute to acidification. Also for these emissions, the Swedish guidelines will be made more stringent during the 90's. The first installation of a de-NOx-unit in Sweden will be made at the coal-fired CHP-plant in Västerås. This SCR of high-dust type is expected to be in operation in October 1991.

An environmental tax for emission of nitrogen oxides will be introduced on January 1, 1992. The fee will be 40SEK per kg nitrogen dioxide and will only consider large power and heat generators. The fees will be paid back according to the amounts of power and heat generated. In this way, boilers with low specific emissions will receive money from boilers with high specific emissions.

The greenhouse effect

The global pollution problem of a climate change on the earth caused by global warming due to the greenhouse gases (carbon dioxide, methane, CFC, and nitrous oxide) is a problem more difficult to solve than urban air quality and acidification.

This global energy problem has now been considered in the Swedish energy tax system. Partly replacing the existing energy tax, the new carbon dioxide tax of 250 SEK per ton CO2 was introduced on January I, 1991.

Reduction of the use of CFC also affects Swedish district heating, since CFC is used as a working medium in the large heat pumps and as a blowing agent for polyurethane foam, used in the prefabricated distribution pipes. In order to promote alternatives to CFC, some municipal authorities have reserved a fraction of the annual purchase volume for non-CFC distribution pipes.

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