Black carbon — Possibilities to reduce emissions and potential effects

The present report emerge from the Swedish EPA project ?Black carbon — possibilities to reduce emissions and potential effects? to obtain an overall assessment of the opportunities and costs for reducing emissions of "soot" (black carbon - BC) in Sweden and its effects on health, ecosystems and climate. The basic analytical methods and techniques are described and reviewed. Existing and upcoming standards are described. The national BC emission inventory has been evaluated through a thorough basic review of the underlying data and processes as well as comparison with other inventories. The report identifies scientific and technological needs (such as methods for emission estimates and emission measurement) needed to implement mitigation measures and assess its impact.The following major conclusions emerge from this report concerning BC and Organic Carbon (OC);Standardized sampling, measurement and analytic methods for BC and OC are underway. Some major networks have already developed standardized methods giving high quality data. A more general standardization will ensure comparability between networks. So future measurements will have less uncertainty and data should be comparable. However this also means that historic data always shall be used with caution. The total BC and OC emissions reported by different inventories agree fairly well, e.g. results from the GAINS scenario estimates and national inventory agree within 30 — 40 % but estimates of major source types can differ with more than a factor 2. This must be investigated as such errors can affect the mitigation policy. Investigations have been started.There is a great need for national projections for 2020 and 2030 for BC but also the other related climate forcing air pollutants.Other climate forcing air pollutants are besides BC and other particle components and ozone. Besides that they affect climate they have a short life time in the atmosphere, thus called Short Lived Climate Forcing compounds (SLCF). Included in the SLCFs are also methane as it affects ozone chemistry even though it has an intermediate atmospheric life time. Inventories and projections on national policy implementation plans have to be developed keeping in mind that climate and health effects depend not on one component only, e.g. soot but rather a mix of different components. The climate effects can be best reduced by a decrease of CO2 and SLCF, while health effects can be reduced by reduced emissions of particles and ozone precursors. The inventories thus have to include the emissions of all these components for all available reduction technologies to facilitate the development of the best abatement strategy. The analysis shows that all techniques involving combustion should be reviewed concerning emissions of all mentioned components.It is clearly shown that regulation of SLCF can give co-beneficial effects on climate, health and ecosystem. However it cannot replace the abatement of long-lived climate forcers but rather increase the climate response to the abatements. The reductions needed for 2050 and beyond have to be large. Combustion is the basic process in the major common sources 6 for CO2, O3-precursors and particles including BC. Combustion has to be questioned as a part of future sustainable transport systems, energy and heat production.The Swedish abatement costs for different SLCF abatement options varied strongly, in the hypothetical scenarios. However the same abatement options show up as the most cost effective in all scenarios. The three most cost effective options covered about 30% of the present emissions. The most cost effective measures found, e.g. decreasing BC emissions from power production and renewing of domestic fuel wood boilers, are found to be in the same range as CO2 ETS price projected for Sweden in 2020. The cost estimates were in line with other studies. Still, the measures studied represent only a very small fraction of all options available to reduce BC emissions. The cost effectiveness of more alternatives in both the mobile and stationary sectors should be assessed. Fuel efficiency improvements, fuel shifts, as well as scrapping schemes are all potentially interesting options. In conclusion, the options analyzed in this study are found to be effective complements, both from health and climate point of view.