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No. 322: Health effects and external costs of emissions from straw boilers

Jensen, S.S., Brandt, J., Christensen, J.H., Frohn, L.M., Plejdrup, M.S., Nielsen, O.-K., Løfstrøm, P. 2019. Helbredseffekter og eksterne omkostninger af emissioner fra halmfyr. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 44 s. - Videnskabelig rapport nr. 322. dce2.au.dk/pub/SR322.pdf 


Purpose and background

The aim of the project is to estimate the health effects and associated external costs of emissions from straw-fired boilers in Denmark. The external costs are the social costs of health effects due to air pollution from straw-fired boilers.

The study

Emissions from straw-fired boilers

The total emissions from straw-fired boilers are calculated for 2016 based on the straw consumption, as well as updated emission factors (Nielsen & Plejdrup, 2017). An emission factor is the emission of air pollution per unit of energy consumed. Emissions are geographically distributed across 1 km x 1 km grid cells in Denmark using the SPREAD model (Plejdrup et al., 2018). In this way, emissions in the national emission inventory are allocated geographically based on different geographical allocation keys.

Health effects and external costs

Air quality models are used to estimate how much emissions from straw-fired boilers in Denmark contribute to the background concentrations calculated with a spatial resolution of 1 km x 1 km. The used models are DEHM (Danish Eulerian Hemispheric Model) and UBM (Urban Background Model). The health effects and external costs are calculated with the EVA-system (Economic Valuation of Air Pollution) based on the contribution to background concentrations. The calculations are carried out for the five administrative regions in Denmark, as well as different population densities. Hence, it is possible to differentiate the external costs of straw-fired boilers depending on their location and to calculate unit costs of emissions. Unit costs are the external costs per kg emission at a given location. DCE-Danish Centre for Environment and Energy under Aarhus University has developed the above models.

Distances from straw-fired boilers to dwellings and to B-values

How many people that lives within various distances of straw-fired boilers has been calculated, and this is assessed in relation to the distance requirements from straw-fired boilers to the nearest neighbour, as set out of the Danish Environmental Protection Agency in an earlier study (Løfstrøm, 2017). For practical reasons, the requirements for the chimney height of straw-fired boilers have been formulated indirectly as a distance to the nearest neighbour in relation to a specific straw-fired boiler. The distance requirement is calculated with the OML-model as the maximum distance, where the B-value is respected. The B-value (concentration contribution value) is a threshold value for an emitting plant and is the maximum concentration contribution of air pollution to the surroundings. B-values are laid down in a guideline by the Environmental Protection Agency (Miljøstyrelsen, 2016) and guidelines for demonstration of compliance are also described (Miljøstyrelsen, 2001).

As the regulation based on distances and B-value is very specific to Denmark it has not been summarised in the English summary.

The main conclusions

Emission from straw-fired boilers

The total straw consumption in 2016 is 4,958 TJ with approx. 60% on home heating and 40% for agricultural purposes. Emissions of nitrogen oxides (NOx), sulphur dioxide (SO2), carbon monoxide (CO), ammonia (NH3), volatile organic compounds (NMVOC) as well as primarily emitted particles (PPM2.5) are compiled and applied for subsequent air quality calculations.

Emissions from straw-fired boilers are compared with the emissions from residential wood combustion. The proportion of emissions from straw burning in relation to wood burning is 13% for CO, 17% for particles, 24% for NH3, 25% for NOx, 28% for NMVOC, 131% for SO2 and 175% for particles.

Health effects

The total number of premature deaths in Denmark due to emissions from straw-fired boilers in Denmark in 2016 is about 100.

In addition, morbidity in the form of hospital admissions due to respiratory and cardiovascular diseases, episodes of asthma and bronchitis, loss of work days, days with reduced activity (sick days), days with reduced activity, as well as lung cancer.

Total external costs

The total external costs in Denmark associated with emissions from straw-fired boilers are DKK 1,757 mill. It is distributed in the following way: DKK 78 mill. due to NOx emissions, DKK 23 mill. due to SO2 emissions and DKK 1,656 mill. due to particle emissions. The total external costs across administrative regions are between DKK 261 and DKK 398 mill. The Capital Region of Denmark has the highest total cost due to a high population density, though emissions are the lowest. The lowest total cost is in the Central Denmark Region due to low population density, although emissions are the highest.

Unit costs

Unit costs of emissions from straw-fired boilers are calculated for the 5 Danish administrative regions (the island of Bornholm separately), as well as for 4 categories of population densities (inhabitants/km2): <100, 100–1,500, 1,500-3,000 and over 3,000. Unit costs are subdivided into a local and a regional contribution. The local contribution is health effect costs within 25 km of those grid cells in a given population density category calculated with UBM, while the regional contribution is the rest calculated with the DEHM. The regional contribution includes both external costs in Denmark and abroad. The sum of the contribution from the regional scale and local scale is the total health costs.

As expected, the unit costs increase with increasing population density. The highest unit cost is in the Capital Region of Denmark due to high population density, and the lowest is at the island of Bornholm due to low population density. The highest unit cost is for the emission of particles in the Capital Region of Denmark for population densities of 100-1500 inhabitants per km2, approx. DKK 38,500 per kg of particulate emission.

In many cases, the local contribution is greater than the regional contributions.

The total unit costs for emissions in Denmark have been distributed to costs in Denmark and to costs abroad. For NOx and SO2 approx. 1/3 of the total unit costs are attributed to Denmark and 2/3 falls in foreign countries. For the unit cost of particulate matter, it is approx. 3/4 in Denmark and 1/4 abroad.

Distances from straw-fired boilers to dwellings

7,441 straw-fired boilers are distributed at 7,418 addresses in 2017. How many persons who live within respectively 100 m, 200 m, 300 m and 500 m from a straw-fired boiler has been calculated in a spatial analysis using a geographical information system (GIS). Number of persons at place of residence originates from the Danish Civil Registration System (CPR) from 24. April 2017. Approx. 38,000 people lives within 100 m (0.7% of Denmark's population), 85,000 within 200 m (1.5%), 153,000 within 300 m (2.7%) and 342,000 within 500 m (6.1%). Detailed analysis of the results shows that there are between 1 and 2,799 persons living within 500 metres of straw-fired boilers, and on average 19 addresses within 500 metres of straw-fired boilers.