Black Carbon Emissions From Diesel Engines - Technical And Policy Options For Reduction Dr Richard O Sullivan 22 March 2012
OVERVIEW OF PRESENTATION The significance of Diesel engine derived black carbon (BC) in Europe Measures that have already been taken to reduce Diesel particulate matter (PM) and BC How much elemental carbon (EC) does Diesel PM contain? Exhaust aftertreatment technology to reduce Diesel PM Policy measures to tackle Diesel PM emissions
WHERE DOES THE BLACK CARBON COME FROM? SOURCES AND GEOGRAPHIC DISTRIBUTION EU emissions remain significant, despite historic reductions In regions where agricultural burning is controlled (Europe, North America), diesel higher proportion of total (>50%)
DIESEL-DERIVED PM IS A SIGNIFICANT HEALTH CONCERN 1000mm = 1m 1000µm = 1mm 1000nm = 1µm Diesel PM is recognised by California Air Resources Board as a toxic air contaminant, and diesel engine exhaust is included in California list of cancercausing chemicals There is no safe threshold level below which health damage does not occur (WHO) 50 nm TEM of Diesel engine exhaust particulate PHOTOS BY B. GROBETY PM 10 < 10µm
HOW DAMAGING TO OUR HEALTH IS PM 10? Excerpt From House of Commons Environmental Report 2010
IS BC FROM DIESEL ENGINE WORSE FOR GLOBAL WARMING THAN FROM OTHER SOURCES? Diesel road/non-road fuel in Europe has <10ppm sulphur Diesel engine-derived PM has low levels of sulphate In process of minimising PM emissions, HC levels are low Diesel engine-derived soot often has high levels of carbon Process of minimising soot emissions by engine improvements also produces more smaller particles Elemental carbon adsorbs more solar energy than other components of combustion-derived particles High surface area of small particles must also lead to high adsorption of solar energy Diesel engine-derived BC would be relatively more warming than other sources
EXAMPLE OF BC CONTRIBUTION FOR A SPECIFIC VEHICLE Euro III double deck bus tested over MLTB on chassis dyno CO2 g/km over cycle 1500 PM g/km over cycle 0.35 Typical %C in PM 70 Net BC g/km in PM 0.245 GWP of BC over 20 years* 2000 Net effect of PM as CO2 g/km equivalents 490 GWP as % of CO2 emissions 33% *Bond estimate for US Senate hearing 2007
DEVELOPMENT OF DIESEL PASSENGER CAR LEGISLATION IN EUROPE mg/km 3000 CO 2500 2000 HC+NOx NOx PM x 10 1500 DOC 1000 500 CSF SCR or LNT 0 Euro 1 1993 Euro 2 1997 Euro 3 2000 Euro 4 2005 Euro 5 2009 Euro 6 2014
PM CHEMISTRY LIGHT DUTY DIESEL VEHICLES All tests on ULSD: E2 & E3 ~35ppm S;E4 & E5 ~10ppm S mg/km Technology Level Elemental carbon fraction of PM dominant in non-dpf applications Post DPF emissions dominated by volatiles; EC levels determined by fill state during test and substrate characteristics Graphs Courtesy of Ricardo
PM EMISSIONS AND CHEMISTRY SPARK IGNITION Vehicles 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% E2 PFI E3 PFI E4 PFI E3 (GDI) E4 (GDI lean) E5 GDI Stoich SO4 16.00 mg/km 16.00 14.00 14.00 12.00 H2O&[SO4] 12.00 10.00 NO3 8.00 10.00 6.00 8.00 Fuel HC 4.00 6.00 2.00 Oil HC 4.000.00 2.00 Carbonaceous remainder 0.00 PM (mg/km) PM (mg/km) 14.55 7.98 SO4 H2O&[SO4] NO3 Fuel HC Oil HC 1.45 0.44 E2 PFI 0.49 E3 PFI 0.20 E4 PFI E3 (GDI) E4 (GDI Carbonaceous E5 GDI lean) remainder E2 PFI E3 PFI E4 PFI E3 Stoich (GDI) E4 (GDI E5 GDI lean) Stoich Gasoline-fuelled vehicles have very low particulate levels with low elemental carbon content Exception is GDI technology Graphs Courtesy of Ricardo
EUROPEAN HEAVY DUTY DIESEL LEGISLATION
PM EMISSIONS AND CHEMISTRY HD DIESEL ENGINES (ETC) 200.00 180.00 160.00 140.00 120.00 100.00 80.00 60.00 40.00 20.00 0.00 185.0 82.0 EI (R49) EII (R49) Pm (mg/km) PM (mg/kwhr) 111.0 96.2 12.6 EII EIII CNG (EIII) Pm (mg/km) 21.7 26.2 1.0 EIV EV EVI (DPF) 100% 90% 200.00 80% 70% 60% 150.00 mg/km 50% 40% 100.00 30% 20% 50.00 10% 0% 0.00 EI EII Technology EII Level (R49) EI (R49) EII (R49) EIII (R49) EII CNG EIII EIV EV (EIII) CNG (EIII) EIV EV EVI (DPF) EVI (DPF) SO4 SO4 H2O&[SO4] H2O&[SO4] NO3 NO3 Fuel Fuel HC HC Oil Oil HC HC Carbonaceous remainder Pm reduces step-wise with technology increments except Euro IV to V There is evidence (Kittelson) that Diesel engines meeting lower PM limits produce more smaller particles DPF will be essential for Euro VI due to PN limit Graphs Courtesy of Ricardo
DIESEL ENGINE EXHAUST EMISSIONS AFTERTREATMENT Diesel Oxidation Catalyst (DOC) to reduce HC (gaseous and SOF) and CO Partial Filters give partial removal of PM % Removal 100 90 80 70 60 50 40 30 20 10 0 PM CO HC Measured over US FTP using ULSD DOC only DOC plus Partial Filter Courtesy of Emitec
EFFECTIVENESS OF DIFFERENT AFTERTREATMENT TYPES Wall flow DPF technology is most effective treatment for reducing PM, EC and PN
PARTICULATE MATTER (PM) REDUCTION Wall Flow Diesel Particulate Filter Alternate channels at either end of the substrate are blocked Exhaust gas is forced through the walls between the substrate channels and PM (soot) is deposited on the walls and trapped Autocatalyst A catalyst can be applied to the filter to produce a Catalysed Soot Filter (CSF) DPF
POLLUTANT REDUCTION FROM CRT -SYSTEM EU I ENGINE, ESC CYCLE 5 4 3 2 1 0 HC*10 CO NOx/10 PM*10 Engine out (g/kwh) 1.62 0.989 0.7018 1.63 CRT (g/kwh) 0.03 0.002 0.6874 0.08 Euro-V (g/kwh) 4.6 1.5 0.2 0.2 Conversion (%) 98% 100% 0% 96%
FILTER REGENERATION Carbon-derived PM is removed from the filter by reaction with oxygen or nitrogen dioxide Prevents blocking, ensures efficiency of filter Active Regeneration Combustion with O 2 at 600 o C ACTIVE PASSIVE C + O 2 CO 2 Passive Regeneration Combustion with NO 2 from approx. 250-300 o C C + 2NO 2 CO 2 + 2NO
BLACK CARBON REDUCTION TECHNOLOGY For developed countries control of Diesel BC would have the greatest effect Diesel Particulate Filters (DPFs) reduce BC in diesel exhaust by 99% Currently widely fitted to new passenger cars and will be fitted to trucks from EU VI BUT further opportunities Retrofit to diesel in current road transport fleets Construction and other non-road machines 1.20 1.00 Survival Probability 0.80 0.60 0.40 Trucks Buses 0.20 0.00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Years
DPF RETROFIT WHAT S BEEN DONE? Low Emission Zones London Euro IV PM for heavy duty vehicles Small number of other cities on much smaller scale Bus Fleet Retrofit London CRT systems fitted to 8,000 buses in early 2000s Oxford, Paris, Berlin, Sweden, USA, Hong Kong, Tokyo (approx 200,000 JM retrofit systems) Non-Road Retrofit Thousands of construction machines in Switzerland, USA retrofitted with filter systems. Other European countries to a lesser extent
POSSIBLE ACTION DPF technology is well proven and has been applied widely to new and existing diesel engines for many years Tighter particulate mass and number limits for new vehicles and machines will increase the use of DPF and decrease emissions of BC Can be accelerated scrappage schemes Retrofit of existing vehicles and machines can be encouraged or mandated funding and tax incentives low emission zones or other local compliance schemes