StatoilHydro’s environmental impact factor (EIF) toolkit for assessing the potentially harmful impact of pollutants has been extended to include emissions to the air and their impact on land and water environments.
The most important consideration is the need to reduce the emission and deposition of nitrogen oxides (NOx) in line with international agreements.
These include the IPPC directive, in force from 2007, and the Gothenburg protocol due to take effect in 2010.
The preferred route is to examine the environmental, economic and social benefits of various remedial measures as a basis for making the right choices.
Environmental components incorporated in the EIF-Air module are:
- deposition of nitrogen (and sulphur, where appropriate) and its impact on vegetation
- acidification of surface water and soils
- production of tropospheric ozone resulting from the combined emissions of nitrogen oxides
- volatile organic compounds (VOCs).
Attempts to evaluate the impact of nitrogen oxide emissions from single sources are complicated by the fact that deposits originate from a variety of sources and geographical areas, and may have travelled considerable distances through the air.
Comparison of EIF values on an offshore platform and a supply ship - per tonne of nitrogen oxide emissions from an offshore platform (left) and a supply ship (right).
Based on broadly similar lines to its marine predecessors, the EIF-Air technique involves:
- calculating the distribution of pollutant concentrations from source to deposit using atmospheric dispersion models
- comparing critical loads and levels with concentrations and deposition rates calculated for different emission reduction strategies
- generating EIF values for air for each route and adding them up over the affected area under investigation.
This method has so far been tested on various emission reduction scenarios for land-based and offshore installations, and for a supply ship plying between StatoilHydro’s Mongstad refinery on the west coast of Norway and a production platform in the Tampen area of the North Sea.
The results show that EIF values per tonne of nitrogen oxide emissions from the supply vessel are nearly three times those for the offshore platform.
Reducing nitrogen emissions from the supply ship should be far more beneficial to mainland Norway in environmental terms than an equivalent reduction from the offshore platform.
