Emission estimates for some acidifying and greenhouse gases and options for their control in Finland: Dissertation

This thesis presents estimates and options for control of anthropogenic ammonia (NH3), methane (CH4), nitrous oxide (N2O) and some halocarbon emissions in Finland. Ammonia is an air pollutant which contributes to both acidification and nitrogen eutrophication of ecosystems. Its emissions are mainly caused by livestock manure. In Finland the anthropogenic emissions of NH3 have been estimated to be approximately 44 Gg in 1985 and 43 Gg in 1990. In the 1990's the emissions have declined due to the reduced number of cattle and voluntary implementation of emission reducing measures. The impact of NH3 emissions on acidification is serious but in Finland it is less than the impact of the other acidifying gases sulphur dioxide (SO2) and nitrogen oxides (NOx). All three gases and their transformation products are transported by the atmosphere up to distances of hundreds or even more than a thousand kilometres. NH3 emissions can be reduced with relatively cost-effective measures and the measures can partly replace the implementation of more costly abatement measures on SO2 and NOx emissions needed to lower the acidifying deposition in Finland. The other gases studied in this thesis are greenhouse gases. Some of the gases also deplete stratospheric ozone. Finnish anthropogenic CH4 emissions have been estimated to be around 250 Gg per year during the 1990's. The emissions come mainly from landfills and agricultural sources (enteric fermentation and manure). The significance of other CH4 sources in Finland is minor. The potential to reduce the Finnish CH4 emissions is estimated to be good. Landfill gas recovery offers an option to reduce the emissions significantly at negligible cost if the energy produced can be utilised in electricity and/or heat production. Measures directed at reducing the emissions from livestock manure management are more costly, and the achievable reduction in the emissions small. The potential to reduce the CH4 emissions from enteric fermentation in Finland is not known. If measures to reduce these emissions prove efficient and economically promising in future studies, the total reduction in the Finnish CH4 emissions will be higher and in the long run the halving of the emission level of 1990 seems achievable. The anthropogenic N2O emissions in Finland are considerably smaller than the CH4 emissions, around 20 Gg per year during the 1990's, but the greenhouse impact of the Finnish N2O emissions is of similar magnitude as that of the Finnish CH4 emissions. The most important anthropogenic N2O emission sources in Finland are nitrogen fertilisation, nitric acid production and burning processes in the energy sector. The indirect emissions caused by nitrogen deposition due to NH3 and NOx emissions are also of significance. The N2O emissions are estimated to grow due to the increasing use of fluidized bed combustion and catalytic converters in the energy sector. These otherwise environmentally friendly technologies produce significantly more N2O than the corresponding conventional technologies. Measures for N2O emission control are not known very well and many of the measures are still at an experimental stage. Promising measures to reduce the N2O emissions from nitric acid production and fluidized bed combustion have been put forward but plant scale applications of the measures are still lacking. If the measures can be implemented on plant scale, emission reductions of the same order of magnitude as the estimated growth in the emissions are anticipated. The CFCs and other considered halocarbons are already partly phased out. The halocarbons that destroy stratospheric O3 are subject to regulations under the Montreal protocol and in Finland most of the consumption ceased in 1996. The O3 depleting substances are partly substituted with substances that are effective greenhouse gases, the most important of which are the HFCs. The emission estimates and impact analyses suggest that the importance of the HFCs could become more significant in the next century if the emissions are allowed to grow unrestricted. The Finnish non-CO2 greenhouse gas emissions contribute significantly to the anthropogenic greenhouse impact caused by the Finnish emissions. In the future the impact caused by the CO2 emissions will grow in importance compared with the non-CO2 greenhouse gases. The warming impact caused by methane, CFCs and HCFCs is estimated to decrease, whereas that of N2O and HFCs is expected to grow.