A two-wheel emission inventory for West Africa for the year 2002

Transcription

1 Eric-Michel ASSAMOI* and Catherine LIOUSSE** ; Laboratoire d Aérologie, CNRS, Toulouse, France A two-wheel emission inventory for West Africa for the year 2002

2 Anthropogenic pollution : a real concern in West African megacities though still largely undocumented

3 BLACK CARBON (BC) MEASUREMENTS : High concentrations at Bamako, Mali BC (!gc/m3) at Bamako (Mali) :50 16:20 21:20 2:20 7:20 14:15 19:15 0:25 5:25 10:25 17:55 22:55 4:35 9:40 14:40 19:40 0:40 5:45 10:45 16:15 22:10 5:20 22:30 5:20 16:00 22:25 5:25 10:40 16:40 0:35 6:15 2:45 8:30 14:15 19:25 1:05 6:15 12:00 17:30 23:40 5:00 Bamako Beijing Paris April, 09, 2008 April, 23, 2008 From Liousse, Galy, Diop, Ndiaye et al., POLCA program

4 2 wheel vehicles highly contribute to such high air pollution in Western Africa Why? - Low road quality. - Adulterated petrol sold in Nigeria, Benin and Togo. - Deregulation of the public transport sector. - Economic solution : increasing number of Asian motorcycles «Jakartas» 2 stroke engines twice cheaper than motorcycles from Europe. Are these emissions really accounted for in present inventories? : Data are quite few, not consistent and sometimes not «official» (specially in Benin with smuggled oil...) => In this work, we propose a first inventory based on several assumptions with maximum and minimum hypotheses.

5 TWO-WHEEL VEHICLE EMISSION INVENTORIES FOR THE YEAR 2002 over West Africa 16 countries E i,j = C i x EF i,j Where E i,j is total emissions in g, C i, motor gasoline fuel consumptions in kg, and EF i,j emission factors in g/kg, for country i and aerosol species j (BC or OCp). Motor gasoline fuel consumption estimation (C i ) Estimate the number of two-wheel vehicles Number of days per week of two-wheel vehicles circulation Daily consumptions Fuel density

6 1- Estimate the number of two-wheel vehicles whether published data (left) or fully evaluated(**) from RATIO (right) COUNTRIES NUMBER OF TWO-WHEEL VEHICLES COUNTRIES ESTIMATED NUMBER OF TWO-WHEEL VEHICLES BENIN 320,000 BURKINA FASO 300,000 CAMEROON 53,000 CHAD 16,000 MALI 300,000 NIGER 5,000 NIGERIA 1,309,000 TOGO 90,000 GAMBIA** 1,026 12,578 GHANA** 11, ,758 GUINEA** 1,827 22,392 GUINEA-BISSAU** ,625 IVORY-COAST** 41, ,177 LIBERIA** 1,159 14,205 SENEGAL** 13, ,739 SIERRA-LEONE** 1,319 16,170 RATIO = number of two-wheel vehicles / number of four-wheel vehicles Minimum assumption = Niger RATIO (minimum of number of two-wheel vehicles) : 0.12 Maximum assumption = Nigeria RATIO (maximum of number of two-wheel vehicles) : 1.44

7 2) Characteristics in the minimum and maximum assumptions Minimum assumption Maximum assumption clean two wheels «motorcycletaxis» clean two wheels «motorcycle -taxis» Number of traffic day(s) per week Daily consumptions (in litres) Fuel density (kg/m 3 ) 5 days per week 7 days per week % oil : ρ = % oil : ρ = 757.8

8 New emission factors (EF i,j ) Direct measurements of emission factors example zems in Cotonou (Benin): CO/CO2 = 0.42 EF(BC) = 2.31 g/kg EF(OCp) =30.56 g/kg In situ urban emissions measurements in Cotonou - AMMA, May 2005 Typical EF traffic values in developed countries: 0.28 for BC and 7.36 for OCp Minimum assumption Maximum assumption Emission factors (g/kg) (Guinot et al., 2009) BC = 0.28 OC = 7.36 BC = 2.31 OC = 30.56

9 IMPORTANCE OF FUEL CONSUMPTION DUE TO TWO- WHEEL VEHICLES : mini./maxi. (in tons per year) Differences between the maxi. and mini. assumptions variable : in Niger = 2,220 tons in Nigeria = 581,110 tons Relative differences (maxi. mini. / maxi.) 97% in countries with estimated number of two-wheel vehicles 64% in countries with available number of two-wheel vehicles 324, ,116

10 CONTRIBUTIONS TO BC EMISSIONS DUE TO TWO-WHEEL VEHICLES : mini. / maxi. (in tons per year) Differences between the maxi. and mini. assumptions variable : in Niger = 7.6 tons in Nigeria = 1,998.3 tons Relative differences (maxi. mini. / maxi.) 96% in countries with available numbers of two-wheel vehicles 2,089 EF(MO) in the maxi. assumption is ~8 times greater than in the mini. assumption

11 CONTRIBUTIONS TO OCp EMISSIONS DUE TO TWO-WHEEL VEHICLES : mini. / maxi. (in tons per year) Differences between the maxi. and mini. assumptions variable : in Niger = 96.5 tons in Nigeria = 25,273.1 tons Relative differences (maxi. mini. / maxi.) 91% in countries with available numbers of two-wheel vehicles 6,761 27,657 EF(MO) in the maxi. assumption is ~4 times greater than in the mini. assumption Much higher impact for OCp than for BC for 2 stroke motorbikes

12 COMPARISON OF ALL TRAFFIC (BOND et al., 2004 and JUNKER and LIOUSSE, 2008) VS. OUR ASSUMPTIONS FOR MOTOR GASOLINE Bond et al., 2004 Junker and Liousse, 2008 vs. mini. assumption vs. maxi. assumption vs. mini. assumption vs. maxi. assumption (%) (%) (%) (%) Consumption BC emissions OCp emissions Example for OCp comparisons for all West African countries

13 New spatialization at 0.25 x 0.25 resolution (vs. normalized population densities, SEDAC 2005) JL, 2008 JL, our maximum assumption tons/year 1,265 tons/year 5,067 tons/year maximum : 39 tons/year maximum : 122 tons/year JL,2008 JL, our maximum assumption tons/year 6,157 tons/year 56,502 tons/year maximum : 191 tons/year maximum : 1281 tons/year

14 CONCLUSION Large underestimates of fuel consumptions in West Africa within the global database. This work, focused on two-wheel emissions, shows the urgent need to integrate African specificities in BC and OCp emissions (both on fuel consumptions and emission factors). But, high uncertainties (cf. the min. and max. assumptions) => strong message to improve official data in each country. More generally, all traffic emissions need to be constantly updated not only two-wheel vehicles but also trucks, buses, for motor gasoline and also for diesel. From this work we can stress a new emission «hot spot» along the coast of the Guinean Gulf and north of Nigeria this «hot spot» is expected to increase in future projections in case of no traffic regulation.

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