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
PM10 < 10µm
HOW DAMAGING TO OUR HEALTH IS PM10?
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
*Bond estimate for US Senate hearing 2007
33%
DEVELOPMENT OF DIESEL PASSENGER CAR
LEGISLATION IN EUROPE
mg/km
3000
CO
HC+NOx
NOx
PM x 10
2500
2000
1500
DOC
1000
CSF
SCR or LNT
500
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%
PM (mg/km)
16.00
SO4
H2O&[SO4]
mg/km
12.00
14.00
10.00
12.00
NO3
SO4
14.00
16.00
14.55
H2O&[SO4]
PM (mg/km)
8.00
10.00
7.98
6.00
NO3
8.00
Fuel HC
4.00
Fuel HC
6.00
2.00
Oil HC
E2 PFI E3 PFI
E4 PFI
4.000.00
2.00
E3 (GDI) E4 (GDI
E5 GDI
lean) Stoich
Carbonaceous
remainder
Oil HC
0.44
E2 PFI
0.00
E2 PFI
0.49
E3 PFI E4 PFI
E3 PFI
1.45
0.20
E3 (GDI) E4 (GDI
E5 GDI
E4 PFIlean) E3Stoich
(GDI)
E4 (GDI
lean)
• Gasoline-fuelled vehicles have very low particulate levels with
low elemental carbon content
• Exception is GDI technology
Graphs Courtesy of Ricardo
Carbonaceous
remainder
E5 GDI
Stoich
EUROPEAN HEAVY DUTY DIESEL LEGISLATION
PM EMISSIONS AND CHEMISTRY HD DIESEL
ENGINES (ETC)
100%
90%
200.00
80%
70%
150.00
60%
50%
mg/km
40%
100.00
30%
20%
50.00
10%
0%
Pm (mg/km)
PM (mg/kWhr)
200.00
180.00
160.00
140.00
120.00
100.00
80.00
60.00
40.00
20.00
0.00
185.0
Pm (mg/km)
111.0
96.2
82.0
12.6
EI (R49)
EII
(R49)
EII
EIII
CNG
(EIII)
21.7
26.2
1.0
EIV
EV
EVI
(DPF)
SO4
SO4
H2O&[SO4]
H2O&[SO4]
NO3
NO3
Fuel
HCHC
Fuel
OilOil
HCHC
0.00
EI
EII
EII EIII Level
Technology
EI (R49)EII (R49)
CNG EIV
(R49)
EII
(R49)
EIII
EV
CNG (EIII) EIV
(EIII)
EV
EVI
EVI (DPF)
(DPF)
Carbonaceous
Carbonaceous
remainder
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
% Removal
• Partial Filters give partial removal of PM
100
90
80
70
60
50
40
30
20
10
0
DOC only
DOC plus Partial Filter
PM
CO
HC
Measured over US FTP using ULSD
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
Autocatalyst
• Alternate channels at either end of
the substrate are blocked
DPF
• Exhaust gas is forced through the walls
between the substrate channels and PM
(soot) is deposited on the walls and trapped
• A catalyst can be applied to the filter to produce a Catalysed
Soot Filter (CSF)
POLLUTANT REDUCTION FROM CRT® -SYSTEM
EU I ENGINE, ESC CYCLE
5
4
3
2
1
0
Engine out (g/kWh)
CRT® (g/kWh)
Euro-V (g/kWh)
Conversion (%)
HC*10
CO
NOx/10
PM*10
1.62
0.03
4.6
98%
0.989
0.002
1.5
100%
0.7018
0.6874
0.2
0%
1.63
0.08
0.2
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
• Active Regeneration
• Combustion with O2 at 600oC
C + O2
CO2
• Passive Regeneration
• Combustion with NO2 from
approx. 250-300oC
C + 2NO2
CO2 + 2NO
PASSIVE
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
Survival Probability
1.00
0.80
Trucks
Buses
0.60
0.40
0.20
0.00
1
2
3
4
5
6
7
8
9
10
11
Years
12
13
14
15
16
17
18
19
20
21
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,
TokyoP(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