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No. 24: Danish emission inventories for road transport and other mobile sources. Inventories until year 2010

Winther, M. 2012. Danish emission inventories for road transport and other mobile sources. Inventories until year 2010. Aarhus University, DCE – Danish Centre for Environment and Energy, 283 pp. Scientific Report from DCE – Danish Centre for Environment and Energy No. 24. http://www2.dmu.dk/Pub/SR24.pdf

Summary

This report explains the emission inventories for road transport and other mobile sources, which are part of the annual Danish emission inventories reported to the UNFCCC (United Nations Framework Convention on Climate Change) and the UNECE LRTAP (United Nations Economic Commission for Europe Long Range Transboundary Pollution) convention. The sub-sectors for other mobile sources are military, railways, navigation, fisheries, civil aviation and non-road machinery in agriculture, forestry, industry and household/gardening.

The emissions of CO2, CH4, N2O, SO2, NOX, NMVOC, CO, NH3, particulate matter (PM), heavy metals, dioxins and PAH are shown in time-series as required by the UNFCCC and the UNECE LRTAP conventions, and grouped according to the UNFCCC Common Reporting Format (CRF) and UNECE National Format for Reporting (NFR) classification codes.

Methodologies

The emission calculations for road transport are made with an internal DCE model, with a structure similar to the European COPERT IV (COmputer Programme to calculate the Emissions from Road Transport) methodology. The emissions are calculated for operationally hot engines, during cold start and fuel evaporation. The model also includes the emission effect of catalyst wear. Input data for vehicle stock and mileage is obtained from DTU Transport, and is grouped according to average fuel consumption and emission behaviour. The emissions are estimated by combining vehicle and annual mileage numbers with hot emission factors, cold:hot ratios and evaporation factors.

For air traffic the 2001-2010 estimates are made on a city-pair level, using flight data from the Danish Transport Authority and landing/take off (LTO) and distance related emission factors from the EMEP/CORINAIR guidebook. For previous years the background data consist of LTO/aircraft type statistics from Copenhagen Airport and total LTO numbers from the Danish Transport Authority. With appropriate assumptions a consistent time-series of emissions is produced back to 1985 using also the findings from a Danish city-pair emission inventory in 1998 (Winther, 2001b).

National sea transport is split into regional ferries, small ferries, freight transport between Denmark and Greenland/Faroe Islands, and other national sea transport. For regional ferries, the fuel consumption and emissions are calculated as a product of number of round trips, sailing time per round trip, engine size, engine load factor and fuel consumption/emission factor. For small ferries, freight transport between Denmark and Greenland/Faroe Islands, and other national sea transport, the calculations are simply fuel based using the fuel consumption findings from Danish surveys in combination with average fuel related emission factors.

Non-road working machines and equipment, and recreational craft are grouped in the following sectors: Agriculture, Forestry, Industry, Household/Gardening, Commercial/Institutional and Inland Waterways. In general the emissions are calculated by combining information on the number of different machine types and their respective load factors, engine sizes, annual working hours and emission factors.

For military, railways and fisheries the emissions are calculated as the product of fuel use and emission factors.

Fuel sales data are obtained from the Danish energy statistics provided by the Danish Energy Agency (DEA). For road transport and aviation the emission results are adjusted in a fuel balance to ensure that all statistical fuel sold is accounted for in the calculations. For national sea transport, the fuel consumption of heavy oil and gas oil is calculated directly by DCE. Fuel adjustments are made in the fishery sector (gas oil) and stationary industry sources (heavy fuel oil) in order to maintain the grand national energy balance. In order to comply with the IPCC guidelines the fuel consumption by vessels between Denmark and Greenland/Faroe Islands are subtracted from the DEA fuel sales figures for international sea transport, and added to the national part of the emission inventories.

Emissions from road transport

Set in relation to the Danish national emission totals, the largest emission shares for road transport are noted for NOX, CO, CO2, NMVOC, TSP, PM2.5 and PM10. In 2010 the emission percentages were 34, 27, 26, 15, 10, 10 and 9, respectively. The emissions of NH3, N2O, CH4 and SO2 have marginal shares of 1.9, 2.0, 0.2 and 0.5 %, respectively.

From 1990 to 2010 the calculated emission changes for CO2 (and fuel use), CH4 and N2O are 30, -74 and 29 %. For NOX, NMVOC, CO and particulates (exhaust only: Size is below PM2.5), the 1985-2010 emission changes are -52, -84, -81, and -65 %.

The most significant emission changes from 1985 to 2010 occur for SO2 and NH3. For SO2 the emission drop is 99 % (due to reduced sulphur content in the diesel fuel), whereas the NH3 emissions increase by 2232 % (due to the introduction of catalyst cars).

Road transport exhaust PM emissions almost solely come from diesel fuelled vehicles. The largest source is passenger cars followed by light duty trucks and heavy-duty vehicles in decreasing order. Since the mid-1990s the emissions from light and heavy duty vehicles have decreased significantly due to gradually stricter Euro emission standards. The environmental benefit of introducing diesel private cars with lower particulate emissions since 1990 is more than outbalanced by an increase in sales of new vehicles in recent years.

The trend in non-exhaust PM follows the traffic growth in general, and in 2010 the TSP (total particulate matter), PM10 and PM2.5 shares were 62, 51 and 36 % of the respective road traffic totals. The non-exhaust PM is gaining more relative importance, in pace with the year by year reductions of exhaust PM.

Historically the emission totals of NOX and especially NMVOC and CO have been dominated by the contributions coming from gasoline passenger cars. However, the emissions from this vehicle type have been reduced since the introduction of gradually more and more emission-efficient catalyst cars from 1990. A negative side effect of this technology though is the increase in N2O and NH3 emissions. The NOX, NMVOC and CO emissions reductions are fortified by the introduction of new gradually stricter Euro emission standards for all other vehicle classes.

Emissions from other mobile sources

For other mobile sources the emissions of NOX, CO, SO2, NMVOC and CO2 have the largest shares of the national totals in 2010. The shares are 33, 33, 14, 13 and 9 %, respectively. The 2010 TSP, PM10 and PM2.5 emission shares are 5, 7 and 8 %, respectively, whereas the emissions of N2O, NH3 and CH4 have marginal shares of 1 % or less in 2010.

From 1990 to 2010 the calculated emission changes for CO2 (and fuel use), CH4 and N2O are -2, 5 and -1 %. The emissions of SO2, particulates (all size fractions), NOX, NMVOC and CO have decreased by 88, 65, 17, 28 and 2 % from 1985 to 2010.

The largest source of NOX and particulate emissions are agriculture/forestry/fisheries, followed by industry and navigation. For NMVOC and CO most of the emissions come from gasoline fuelled working machinery in the commercial/institutional and residential sectors.

Heavy metals

Heavy metal emissions are calculated for fuel and engine oil as well as for tyre, brake and road wear. The road transport shares for copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd) and chromium (Cr) are 94, 71, 59, 22 and 21 % of national totals in 2010. For other mobile sources the nickel (Ni), Arsenic (As) and Pb shares are 39, 15 and 10 %. For the remaining components, the emission shares are less than 6 %.

The most important exhaust related emissions (fuel and engine oil) for road transport (% of national total in brackets) are Zn (19 %), Cd (19 %) and Cr (10 %). The most important wear related emissions are Cu (93 %) and Pb (58 %) almost solely coming from tyre wear, and Zn (52 %) from brake and tyre wear. For other mobile sources, the emissions of Ni and As arise from the use of marine diesel oil and residual oil in fisheries and navigation. The emissions of Pb almost solely come from the use of aviation gasoline.

In general terms the development in emissions follows the trends in fuel/engine oil consumption and vehicle mileage (wear related emissions). It must be noted, however, that there has been an almost 100 % decline in the exhaust related emissions of Pb, due to the phasing out of leaded gasoline fuels until 1994.

PAH’s

The PAH emission shares for road transport and other mobile sources are 3 % or less of the national total in 2010.

Uncertainties

For mobile sources in 2010 the CO2 emissions are determined with the highest accuracy, followed by the CH4, TSP, SO2, PM10, PM2.5, NMVOC, NOX, CO and N2O emissions with increasing levels of uncertainties. The uncertainties are 5, 27, 48, 49, 51, 54, 55, 56, 60 and 152 %, respectively. The uncertainties for the 1990-2010 emission trends are 6, 5, 6, 3, 4, 3, 9, 11, 16 and 54 % for the emissions in the same consecutive order. For NH3, heavy metals and PAH’s the 2010 emissions have uncertainty levels of between 700 and 1000 %. In this case the emission trend uncertainties are significantly lower; still large fluctuations exist between the calculated values for the different emission components.