A R e p o r t o n t h e

P e r f o r m a n c e a n d E m i s s i o n E f f e c t o f

U l t r a L o w S u l p h u r D i e s e l

O n D o u b l e D e c k ( E u r o I ) B u s

M a y 2 0 0 0

N e w W o r l d F i r s t B u s S e r v i c e s L i m i t e d

Environmental Protect ion Department T h e G o v e r n m e n t o f t h e H o n g K o n g

S p e c i a l A d m i n i s t r a t i v e R e g i o n

T a b l e o f C o n t e n t s

Page No.

1. Executive Summary 1

2. Objective 4

3. Introduction 4

3.1 Particulate emission from Buses 4

3.2 ULSD 4

4. Test Program 6

4.1 Sponsorship 6

4.2 Test Period 6

4.3 Test Parameters 6

4.4 Test Fuel 6

4.5 Test Bus 7

4.6 Test Route 7

5. Emission Measurment 8

5.1 Pre-test Arrangements 8

5.2 On-road Test Cycle 8

5.3 Smoky Emission 8

6. Results 9

6.1 Particulate Emission 9

6.2 Smoke test 9

6.3 Fuel Consumption and Maintenance 10

7. Conclusion 11

8. Reference 12

Tables Page No.

Table 1 Specification for Regular Diesel and Ultra

Low Sulphur Diesel (ULSD)

13

Table 2 Particulate Emission Reduction of Euro I Bus

Using ULSD and Catalyst

14

Table 3 Smoke Reduction of EURO I Bus Using

ULSD and Regular Diesel

15

Figures

Figure 1 Euro I Bus Running on ULSD 16

Figure 2 On-Road Bus Exhaust Emission

Measurement

16

Figure 3 Portable Exhaust Emission Analyzers 17

Figure 4 Particulate Collection 17

Figure 5 EURO I Bus Particulate Reduction when

Using ULSD as compared with Regular

0.05% Sulphur Diesel

18

Figure 6 EURO I Bus Smoke Reduction when using

ULSD as compared with Regular 0.05%

Sulphur Diesel

19

1 1

Executive Summary

Ultra low sulphur diesel (“ULSD”) is used in the United Kingdom (“UK”) and

Sweden to reduce particulate emission from diesel exhaust. Up to now,

information on the benefit of using ULSD is mainly based on controlled testing

conditions in laboratories. There is little information on the use of ULSD in diesel

engines under actual road conditions . To study the suitability of ULSD for Hong

Kong and its effect on emission, New World First Bus Services Ltd. (“NWFB”)

and the Environmental Protection Department (“EPD”) jointly sponsored a test

program to compare the operation of a bus running on regular diesel and ULSD

under local environment.

In this program, ULSD with sulphur concentration of about 33 ppm was specially

imported from the UK. An Euro I bus was selected from the NWFB bus fleet for

the particulate and smoke emission tests. In addition, the bus operating

performance such as fuel consumption and maintenance requirement were

recorded and compared with the normal bus fleet that used regular diesel.

The particulate emission of the Euro I bus was measured by an on-road

measurement technique developed by the Emission Measurement Research

Division (“EMRD”) of Environment Canada. The test result showed that when

ULSD was used, particulate emission was reduced by 8.4% compared with

normal sulphur diesel. The emission was reduced by 18.4% when the bus was

equipped with an oxidation catalytic converter.

In addition, free acceleration smoke (“FAS”) tests were conducted under the

supervision of Hong Kong Polytechnic University (“HKPU”). The result showed

that ULSD reduced the smoke emission by 9.4%. When the bus was retrofitted

with a catalytic converter, emission was reduced by 15.4%.

As for the operating performance, the test revealed that the fuel consumption of

the bus running on ULSD was no noticeable difference from that of the Euro I bus

fleet running on regular diesel. Also, there was no noticeable difference in the

maintenance requirement for bus using the two types of diesel.

Overall, the test results showed that when Euro I bus engine operated under the

stop-and-go driving pattern and hill-climbing conditions in Hong Kong, the

particulate and smoke emissions were reduced by switching from regular diesel to

2 2

ULSD. The fuel switch caused no noticeable change in fuel economy and

maintenance requirement either. Although ULSD will normally be introduced

with the availability of Euro IV models in around 2006 (1), early introduction of

ULSD will help to reduce particulate exhaust emission from the diesel vehicles in

Hong Kong.

3 3

1 . A c k n o w l e d g e m e n t s

This project was jointly supported by the New World First Bus Services Ltd and

the Environmental Protection Department. Acknowledgements are due to other

agencies and individuals that played valuable roles in the program.

Angus Craig, Environment Canada - On-road exhaust emission

measurement and data analysis. Dr C. S. Cheung, Polytechnic University - Measurement of exhaust emission

and temperature

4 4

2 . O b j e c t i v e

The objective of this test program was to examine if emission would be reduced by

using ultra low sulphur diesel (“ULSD”) in normal bus operations in Hong Kong

and the suitability of using such fuel for local buses.

3 . I n t r o d u c t i o n

3 . 1 P a r t i c u l a t e e m i s s i o n f r o m B u s e s

Particulate emission from diesel vehicles is a key factor that causes the current air

pollution in Hong Kong. Exhaust emissions from diesel vehicles such as taxis, light

vans, goods vehicles and buses are the major sources of particulate emission.

There are more than 11,000 public buses licensed for operation in Hong Kong and

they account for about 12% of the total vehicular particulate emissions.

Many Hong Kong buses are either Euro I or earlier models. Since the working life

of a bus is about 10 to 15 years, it will take some time to replace these older models

by the more environmental friendly Euro II or Euro III models. In the interim,

there is a need to explore various means to reduce particulate emission from the

current bus fleet to improve the air quality.

3 . 2 U L S D

Using ULSD instead of regular diesel is an acknowledged method to reduce

particulate emission from diesel engines. The low sulphur content will reduce

particulate formation during the combustion process. Countries such as Sweden

and the UK have introduced ULSD ahead of the European Union's 2005 mandate.

As for Hong Kong whose sulphur content limit in diesel is one of the most

stringent in the Asia-Pacific region, the existing legislation already limits sulphur

concentration to not more than 500 ppm. The sulphur level will further be

tightened to 350 ppm by January 2001 to match the future Euro III diesel engine

technology. Though ULSD is available in some European countries, it was not yet

available in Hong Kong or in any other Asian countries.

Numerous publications have shown reduction of particulate emission from diesel

engines by switching to ULSD. However, most of the findings are based on

5 5

laboratory tests with constant engine running condition. For example, studies by

London Transport Bus (2) has shown that the use of ULSD by diesel buses could

reduce particulate emission from diesel exhaust. So far, there is little information

about the benefit of using ULSD under actual road conditions. Also, it is not

known how the local operating conditions - such as stop-and-go downtown traffic

and hill-climbing - affect the emission from ULSD diesel engines. In order to

examine whether early introduction of ULSD to the local market is beneficial,

NWFB and EPD have jointly carried out a test program to investigate the possible

emission reduction and operating performance of Euro I bus running on ULSD

under local environment.

6 6

4 . T e s t P r o g r a m

4 . 1 S p o n s o r s h i p

This project was jointly sponsored by NWFB and EPD.

Apart from providing the test bus, NWFB supplied both ULSD and regular diesel

for the test. A total of 20,000 litres of ULSD were acquired from BP in the UK.

The fuel were shipped in 200L drums and stored at NWFB’s depots. The test bus

was refilled with ULSD manually each day. NWFB was also responsible for

collecting fuel consumption and maintenance data.

EPD was responsible for the project definition and collaboration with EMRD of

Environment Canada to measure on-road exhaust emission (3). In addition, EPD

commissioned HKPU to carry out the free acceleration smoke (FAS)

measurement.

4 . 2 T e s t P e r i o d

The tests commenced in November 1999 and completed by January 2000.

4 . 3 T e s t P a r a m e t e r s

Particulate emission during the on-road testing and the smoke emission were the

major parameters of interest. The data were obtained from emission

measurement when the bus was using either regular diesel or ULSD. To further

assess the bus operation performance, the fuel consumption and maintenance

data such as oil and air filter changes were also collected.

4 . 4 T e s t F u e l s

Both regular diesel and ULSD used in this test program were imported specially

from the UK.

The most important difference between ULSD and regular diesel used in this

project was the sulphur concentration: about 33 ppm for ULSD, 350 ppm for

regular diesel; both are lower than the maximum allowed by the local

specification or legislation. The basic properties of the two diesel types are shown

7 7

in T a b l e 1 .

4 . 5 T e s t B u s

The Euro I bus was equipped with a Cummins Euro I diesel engine and was

selected from the NWFB bus fleet. Prior to the tests, the bus has already

accumulated about 300,000 km and was later retrofitted with a oxidation catalytic

converter to investigate the combined emission reduction effect with ULSD.

F i g u r e 1 shows the NWFB bus selected for the test.

4 . 6 T e s t R o u t e

One major criterion for selecting the bus route for on–road emission

measurement was that the traffic conditions and terrain must closely resemble the

general bus operation conditions in Hong Kong. On this basis, Route 38 was

selected. It is one of the bus routes that serve both the downtown busy commercial

districts like Causeway Bay, covering about 9 km (“downtown section”), and the

hilly terrain of uptown residential areas in the southern part of the Hong Kong

Island, covering about 4 km (“uptown section”). The route requires the bus engine

to operate at low to medium loading conditions in the downtown section and high

loading condition in the uptown section.

8 8

5. Emission Measurement

All emission tests were conducted under three scenarios. The first scenario was to

examined the particulate emission using regular diesel (“baseline scenario”); the

second scenario examined the use of ULSD (“ULSD scenario”); and the third

scenario examined the use of ULSD together with the catalytic converter (“ULSD

+ Catalyst scenario”).

During the on-road emission measurement, the tailpipe of the bus was fitted with

exhaust emission sampling equipment operated by EMRD. The bus exhaust

particulate emissions were measured by bag sampling during the on-road tests

while the smoke emission was obtained by FAS test.

5 . 1 P r e - t e s t A r r a n g e m e n t s

The bus engine underwent regular maintenance services before emission tests

using each type of diesel. Engine oil, hydraulic fluid, air and oil filters were

changed before the tests. Also, during fuel change, the remaining fuel was drained

out from the bus fuel tank and replaced by the other type of diesel. The engine was

kept running for at least 24 hours to ensure the fuel line was completely purged.

5 . 2 O n - r o a d T e s t C y c l e

The bus engine was first fully warmed up through a journey of at least 15 minutes

before conducting the emission test each day. The test was performed at the same

hour to ensure similar traffic pattern for all measurement. Tailpipe emissions

were conducted for each downtown and uptown route and a total of three

measurements were collected for each route by ERMD. The emitted particulates

were trapped by a filter, kept in a sealed container and shipped by EMRD to

Canada for analysis. Figure 2, 3 and 4 illustrate the on-road measurement of

particulate conducted by EMRD.

5 . 3 S m o k e E m i s s i o n

The smoke emission under free acceleration test was supervised by the HKPU. In

addition, smoke emission was also measured after the bus was retrofitted with a

catalytic converter.

9 9

6 . R e s u l t s

6 . 1 P a r t i c u l a t e E m i s s i o n

The test result showed that the levels of particulate emission from the Euro I bus

depended on the sulphur concentrations of the fuel. Under the baseline scenario

when regular diesel was used, the particulate emission was 1.49 g/km and 1.79

g/km for the downtown and uptown sections respectively. Over the whole route,

the weighted particulate emission was 1.58 g/km.

Under the ULSD scenario, the particulate emission was 1.45 g/km and 1.64 g/km

for the downtown and uptown sections representing a reduction of 2.7% and

8.4% respectively below the baseline scenario. Over the whole test route, the level

of particulate emission was 1.51 g/km, a reduction of 4.4%.

Under the ULSD + Catalyst scenario, the particulate emission was 1.27 g/km and

1.46 g/km for the downtown and uptown sections representing a reduction of

14.8% and 18.4% respectively. Over the whole test route, the level of particulate

emission was 1.33 g/km, a reduction of 15.8%.

Overall, the emission test result indicated that when the Euro I bus was running

on ULSD, it emitted less particulate in all conditions regardless of the engine's

loading. The particulate emission of the bus was further reduced by retrofitting

with an oxidation catalyst (4). All the test results are shown in Table 2 and Figure

5 .

It is noteworthy that, in this project, the reduction of particulate emission from

the bus using ULSD was less than the emission reduction test results obtained

overseas. This might be due to the emission testing reported elsewhere mostly

measured in laboratories under well-controlled environment instead of actual

road conditions. Nevertheless, in this test program, the result of the on-road

emission measurement showed that under local conditions , the Euro I bus emitted

less particulate when it was running on ULSD than regular diesel.

6 . 2 S m o k e t e s t

The levels of smoke opacity measured by FAS under baseline, ULSD and ULSD +

10 10

Catalyst scenarios were 47.4 HSU, 42.9 HSU and 40.1 HSU respectively. This

result indicated that the use of ULSD and ULSD + Catalyst reduced the smoke

emission by 9.5% and 15.4% compared with normal diesel. All the test results are

shown in T a b l e 3 and F i g u r e 6 .

6 . 3 F u e l C o n s u m p t i o n a n d M a i n t e n a n c e

During the two-month testing period, both the normal diesel bus fleet and the

ULSD bus consumed about 1.10 L/km of fuel while travelling along the same

route. This indicated that there was no significant change in fuel consumption

when ULSD was used.

In addition, there was no report on any significant changes in maintenance

required by the ULSD bus. The engine oil consumption of the ULSD bus was

about the same as the normal diesel bus. According to the feedback from the bus

drivers, the ULSD bus operated like a normal diesel bus and did not show any

deterioration in performance when ULSD was used.

11 11

7 . C o n c l u s i o n

The particulate emission from the Euro I bus running on ULSD was reduced

when regular diesel was used. The on-road emission test result showed that the

use of ULSD reduced the particulate emission by 8.4%. The reduction was further

improved to 18.4% when the bus was retrofitted with a catalytic converter.

Similarly, the use of ULSD reduced the smoke emission of the Euro I bus by 9.4%

when compared with regular diesel and the smoke was reduced by 15.4% when

bus was equipped with a catalytic converter.

In addition, the use of ULSD did not adversely affect the performance of the bus.

The drivers found no noticeable power loss and the bus operated similarly with

either regular diesel or ULSD. There was no significant change in fuel and engine

oil consumption. Nor was there any change in the maintenance requirement.

Overall, the test results showed that with Euro I engine, the stop-and-go driving

pattern and hill-climbing conditions in Hong Kong, particulate and smoke

emissions were reduced by switching from regular diesel to ULSD. The fuel switch

caused no significant change in fuel economy and maintenance requirement either.

Early introduction and wide application of ULSD should thus be encouraged to

reduce the local air pollution.

May 2000

12 12

8 . R e f e r e n c e :

1. Worldwide Fuel Charter, April 2000

2. Buses: a cleaner Future. London Transport Buses.

3. The impact of Retrofit Exhaust Control Technologies on Emissions from

Heavy-Duty Diesel Construction Equipment. SAE Technical Paper series

1999-01-0110

4. Urban Driving Cycle Results of Retrofitted Diesel Oxidation Catalysts on

Heavy Duty Vehicles. SAE 960134.

13 13

T a b l e 1 C o m p a r i s o n o f S p e c i f i c a t i o n s o n R e g u l a r D i e s e l a n d U l t r a L o w S u l p h u r D i e s e l ( U L S D ) ( F r o m N o v e m b e r 1 9 9 9 t o J a n u a r y 2 0 0 0 )

R e g u l a r D i e s e l U L S D I t e m f o r e x a m i n a t i o n

N W F B S p e c i f i c a t i o n

H o n g K o n g S p e c i f i c a t i o n

A n a l y s i s r e s u l t N W F B S p e c i f i c a t i o n

P r o p o s e d H o n g K o n g

S p e c i f i c a t i o n

A n a l y s i s r e s u l t

C e t a n e N u m b e r ( m i n . ) 50 50 - 51 51 -

C e t a n e I n d e x - - 56 - - 57

V i s c o s i t y @ 4 0 °C (mm 2 / s ) 2 - 4.5 2 – 4.5 3.5 2 – 4.5 2 – 4.5 2.8

T 9 0 357 - 345 - - 335 D i s t i l l a t i o n T e m p e r a t u r e ( °C )

T 9 5 -

370 - 370 345 -

M a x . S u l p h u r C o n t e n t ( p p m )

500 500 355 50 50 33

S p e c i f i c G r a v i t y @ 1 5 °C ( k g / L )

0.82 –0.86 0.82 – 0.86 0.84 0.82 – 0.84 0.835 max. 0.83

B e n z e n e C o n t e n t ( % , v / v ) - - <0.15 - - <0.15

T o t a l A r o m a t i c s C o n t e n t ( % , v / v )

- - 12 - - 12

14

T a b l e 2 Part icu la te Emiss ion Reduct ion o f Euro I Bus Using ULSD and C a t a l y s t

Fuel/EmisionTest Route Downtown (DT) Uptown (UT) Overall (O)

A Baseline(no Catalyst +0.05%S)

1.49 1.79 1.58

B No-catalyst +ULSD(0.005%S)

1.45 1.64 1.51

% Difference -2.7% -8.4% -4.4%

C Catalyst +ULSD(0.005%S)

1.27 1.46 1.33

% Difference -14.8% -18.4% -15.8%

O = DT x 9 + UT x 413

% D i f f e r e n c e ( B ) = B - A

A

% D i f f e r e n c e ( C ) = C - A

A

PM (g/km)

15

T a b l e 3 S m o k e R e d u c t i o n o f E U R O I B u s U s i n g U L S D a n d R e g u l a r D i e s e l

Company New World First Bus Services Ltd.

(License Plate No.: GV9359) Bus/Engine Model Cummins Euro-I Engine (Model No. L10B-252) Diesel Type Regular ULSD ULSD Manufacturer A - Catalyst Muffler No No Yes FAS, Max. smoke opacity (HSU) 47.4 42.9 40.1 % Reduction Smoke 9.5% 15.4%

16

Figure 1 E u r o I B u s R u n n i n g o n U L S D

Figure 2 O n - R o a d B u s E x h a u s t E m i s s i o n M e a s u r e m e n t

17

Figure 3 P o r t a b l e E x h a u s t E m i s s i o n A n a l y z e r s

Figure 4 P a r t i c u l a t e C o l l e c t i o n

18

F i g u r e 5

Euro I Bus Particulate Reduction When Using ULSD As ComparedWith Regular 0.05%S Diesel

2.7%

8.4%

14.8%

18.4%

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

12.0%

14.0%

16.0%

18.0%

20.0%

DT UT

Particulate Reduction %

ULSD CAT+ULSD

DT - DOWNTOWN ROUTE UT - UPTOWN ROUTE ULSD - 50 PPM SULPHUR REGULAR FUEL - 0.05%S DIESEL

19

F i g u r e 6

Euro I Bus Smoke Reduction When Using ULSD As

Compared With Regular 0.05%S Sulphur

9.5

15.4

0

2

4

6

8

10

12

14

16

18

% Smoke Reduction

ULSD ULSD+CAT