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Facts Sheet 5b. Carbon emissions: High speed rail and air

 
Originally February 2007
Updated June 2008,
Preamble added April 2009
Caveat added July 2009
Wp ref. factssheet05bB
CONTENTS
CAVEAT
Preamble
Summary results
Data sources and detailed results
Comment
Radiative forcing
Sources and notes reference aircraft
Appendix 1 Emissions from the UK generating industry

Caveat

The abstract of a paper by Mikhail V Chester and Arpad Horvath illustrates how vital it is to have dust to dust estimates of energy consumptions and emissions.  There we see the estimates of life cycle energy inputs and emissions in the USA add 63% to the tailpipe values for road vehicles, 31% for air and 155% for rail. 

Instead of that nearly all UK emission studies deal with tail pipe emissions alone. Consequently the conclusions of all those studies may turn out to be unsustainable along with policy depending upon them.

Preamble

Those promoting high-speed rail make much of the supposed carbon emission saving that may result if internal air passengers transferred to high-speed rail.  However, the proportion of the nation’s emissions that can be attributed to air or rail is vanishingly small, see below.  Hence, any transfer of passengers from one mode to the other can only have an even more vanishingly small effect.

For that reason alone the emissions argument made by those lobbying for high-speed rail should probably be ignored.

 (This figure is from the White Paper, Delivering a Sustainable Railway, July 2007)

Summary results

The carbon emissions for rail depend on whether the average emissions from the UK generating industry are used, or those relating to coal-fired generation.  The reason for the latter is that large scale electrification may extend the life of coal-fired generation.  In this note values for both assumptions are provided, coal-fired generation emitting twice as much as the industry average.

The emissions for high speed rail are based on a 40% load factor.  The tailpipe values in grams per 100 passenger-km have the range of 4150 to 8300 for a train at 200 kph.  In contrast Ryan Air may return 8475 gms per 100 passenger-km. However, if these values are inflated to provide life cycle values, as suggested in the caveat, the range for rail is 10,600 gms to 21,200 gms and the value for Ryan Air is 11,100 gms.

Against that background it seems premature to claim that high-speed rail will have substantially lower emissions than air travel when precisely the reverse may be the case.

Data sources and detailed results

Except where stated the data which follows relates to tailpipe fuel consumptions and emissions.

Appendix 1 sourced from the BERR, provides (A) circa 150 Tonnes of carbon per GWh (550 tonnes of carbon dioxide) if we assume average emissions or (B) circa 300 Tonnes per GWh (1,100 tonnes of carbon dioxide) if emissions are related to coal-fired generation. In this note we present emission on both bases. However, the coal-fired emission rates may be the more appropriate because, as pointed out by the RSSB in its report on Traction Energy Metrics, July 2007, any large scale increase in electricity supply would prolong the life of coal-fired generation.

The emissions per passenger-km depend on occupancy assumptions.  The RSSB report Traction Energy Metrics, in section 6, assigns a  40% occupancy to intercity rail.  We have used that here although it is said to lead to overcrowding on some trains.  For comparison the average for all trains is 30%. If for service level reasons that should be the target for intercity services then the emissions per passenger-km in Table 1 should be increased by one third.

The emissions per passenger-km for the aircraft assume an occupancy of 80%.  That is above the industry average but below the 84% claimed by Ryanair.  Further, emissions by air cited in table 2 are 10% above those in the source table 3 to allow for refinery energy use and the transport of the fuel to the users.

The fuel consumptions for rail in the following table are from Professor Roger Kemp.  They have been converted to carbon emissions using the emission data cited above. 

 

TABLE 1

High-speed train emissions

KW-h

per 100

 seat-km

Carbon dioxide Gms

(A) average emissions

Carbon dioxide Gms

(B) Coal-fired emissions

per 100

 Seat-km

per 100

 Passenger-km

per 100

 Seat-km

per 100

 passenger-km

Pendolino West Coast at 200 kph: range

3.5

1,925

4,810

3,850

9,720

4

2,200

5,500

4,400

11,000

Class 91 East Coast at 200 kph

3.2

1,660

4,150

3,320

8,300

Eurostar at 300 kph

5

2,750

6875

5,500

13,750

 (Note, Eurostar achieves a higher occupancy than used here and claims electricity from France where 80% is from nuclear.  Hence in Eurostar publicity emission rates are much lower than in this table).

Professor Kemp also cited a diesel HST requiring 0.8 litres per 100 seat-km at 200 kph. The specific gravity of diesel is 0.84 and the CO2 per Kg is 3,150 gms. Hence the carbon dioxide per 100 seat km is 0.8 x 0.84 x 3,150 = 2,117 gms or 5,290 gms per 100 passenger-km at 40% load factor.

Data for air is summarised in table 2.  As noted above the emissions have been increased by 10% above those in the source table 3 to allow for the energy used in refineries and in transporting the fuel to the users. The data (with the exception of Ryanair) overstates the emissions for comparison with rail because of the relatively large amounts of luggage and freight carried by passenger aircraft but not (presumably) by high-speed rail.

 

Table 2

Gms of CO2

Per 100 seat-km

Per 100 passenger-km

Ryanair

6,780

8,475

757-300

7,750

9,690

Fokker F28

19,540

24,420

 Comment

The data in tables 1 and 2 could be used to claim that, if it is emission (B), coal-fired generation, that is relevant and if Ryanair is taken as the model aircraft, then air produces the lower emissions. On the other hand if it is emission (A), the generating industry average, that is relevant, then high-speed rail may claim the lower emission.

Radiative forcing

The emissions from aircraft are often weighted by a factor in the range 1.5 to 3 to allow for the greater radiative forcing arising from high altitude emissions.  However, short haul aircraft spend little time at the altitude where the higher radiative forcing factors apply. Further ground level emissions are said to carry a radiative forcing factor that is usually omitted. Hence when comparing the warming effects of rail compared with air the differences in radiative forcing can probably be ignored.

Sources and notes reference aircraft

The Institute of Energy (0207 467 7100) and others provided the following for aviation fuel:

Calorific value: gross = 46.2 giga-joules per Tonne, Net 46.2 x 0.935 = 43.2

Carbon dioxide:  3.15 Kg of CO2 per Kg of ATF (Jet 1)

Specific gravity range 0.775 to 0.84 providing an average here set to 0.8.

That together with the source data in Table 3 below enables the emission data therein to be calculated. E.g. Ref. the CRJ-700 first item: CO2 per 100 seat-km = (545 x 3.785 x 0.8 x 3,150 x 100)/(334 x 1.6 x 70) = 13,896 gms.

The Aircraft Monitor data in table 3 was recommended to us by Dr Peter Morrell of the Cranfield Institute of Technology. Dr Morrell has also been kind enough to confirm that the parameters and calculations used in this table are in close agreement with his estimate for the B747-200 (the last aircraft cited in table 3).

Fuel consumptions in this table should be increased by 10% to allow for refinery energy use and fuel used in transporting the fuel to the users

 

TABLE 3

Source: The Airline Monitor, August 2002 *

Carbon dioxide gms

Short/medium

haul:

US gals per

block hour

Av. Seats

per flight

Av miles

per flight

Av mph

per 100

seat-km

per 100 pass-km:

80% load

Ryanair

776

189

611

397

6,165

7,707

CRJ-700

545

70

428

334

13,896

17,370

CRJ-100/200

365

50

442

297

14,653

18,316

ERJ-135

312

37

390

261

19,260

24,075

ERJ-140

359

44

387

284

17,127

21,408

ERJ-145

358

50

431

270

15,809

19,761

Avro 85

569

69

297

247

19,903

24,878

Bae 146

623

91

316

258

15,819

19,773

Fokker F28

664

69

430

323

17,761

22,201

DC-9-30

808

101

512

306

15,585

19,482

F-100

658

88

473

293

15,213

19,017

717-200

635

111

415

292

11,679

14,599

MD 90

927

150

811

359

10,262

12,828

737-200

910

115

522

329

14,338

17,923

737-500

704

109

600

334

11,528

14,410

A319

758

123

933

374

9,823

12,279

737-300

730

131

610

333

9,976

12,470

737-400

786

141

663

333

9,979

12,474

A320-200

822

146

1,091

388

8,650

10,813

MD80

956

135

779

351

12,027

15,034

727-200

1281

149

766

354

14,478

18,097

737-800

836

149

1,055

382

8,756

10,945

737-900

801

172

1,075

390

7,118

8,898

A321-200

927

169

1,406

410

7,975

9,969

757-200

1091

182

1,258

402

8,889

11,112

757-300

1191

247

1,084

408

7,045

8,807

A300-600R

1743

228

1,513

413

11,035

13,793

B767-400

1661

272

1,547

429

8,486

10,607

Medium/long-haul

L1011-500

2365

288

2,340

449

10,903

13,629

DC10-10/30/40

2606

284

2,575

461

11,866

14,832

A330

2169

261

3,647

468

10,586

13,232

MD-11

2160

272

3,651

488

9,701

12,126

B767-300

1476

207

2,274

450

9,446

11,808

B767-200

1459

176

2,083

436

11,335

14,168

B777-200

2134

266

3,557

487

9,820

12,276

B747-400

3429

369

4,445

505

10,970

13,712

B747-200

3536

357

3,386

480

12,301

15,377

Further a report in the Times of 8th February 2008 cites the A380 (certified to carry 853 passengers) as emitting 8,000 gms of CO2 per 100 passenger-km when carrying 550 passengers on an 8,000 km trip.

Appendix 1 Emissions from the UK generating industry

Table A1 below and the associated notes provide:

  1. Ratios of primary burn to end user consumption of (a) 1024.8/345.2 = 2.97 in 2005 and (b) 1022.9/344.8 = 2.96 in 2006; leading us to use 3.0 in other calculations.
  2. A fair estimate of the corresponding carbon emission from industry as a whole is 150 Tonnes per GWh delivered to end users or 50 Tonnes per GWh of primary energy burn.  Those numbers correspond to 550 and 183 Tonnes of carbon dioxide.  If it is coal-fired emissions that are relevant then these emissions should be doubled.

TABLE A1 Electricity generating industry: Energy burnt and supplied and emissions

 

Fuel

Source

MtC/Mtoe (a)

Mt of oe burnt (b)

TWh burnt (d)

Carbon

 emission Gt

TWh

supplied (b)

Tonnes C per GWh consumed (e)

 
 

2005

2006

2005

2006

2005

2006

2005

2006

2005

2006

 

Coal

1.029

32.62

36.12

380.57

421.40

33.56

37.16

128.67

143.54

293

289

 

Oil

0.875

1.33

1.62

15.52

18.90

1.16

1.42

4.72

5.20

277

305

 

Gas

0.582

28.7

26.51

334.83

309.28

16.71

15.44

149.78

138.57

125

125

 

Nuclear

0

18.37

16.92

214.32

197.40

0.00

0.00

75.17

69.24

0

0

 

Hydro

0

0.43

0.39

5.02

4.55

0.00

0.00

4.01

3.32

0

0

 

Other renew

0

3.6

3.76

42.00

43.87

0.00

0.00

11.91

12.41

0

0

 

Other fuels

 

2.07

1.48

24.15

17.27

0.00

0.00

4.72

4.03

0

0

 

Imports

 

0.72

0.8

8.40

9.33

0.00

0.00

8.32

9.30

0

0

 

Totals/mean

 

87.84

87.6

1024.8

1022

51.44

54.01

387.3

385.61

149

157

 

Final consumption TWh (c)

345.241

344.85

 

 

 

Notes:

  1. These are Mega Tonnes of Carbon per Mega Tonne of Oil Equivalent as provided by Julian Prime of BERR on 5th October 2007.
  2. Table 5.1 of Energy Trends March 2007.  The Mt of oe burnt is the oil equivalent burnt by the generators.  The TWh supplied is that reaching the grid.
  3. Table 5.2 of Energy Trends March 2007.   The TWh consumed is the electricity reaching users after deducting transmission losses and the generating industry use.
  4. The calorific value of an Oil Equivalent is 42 GJ per tonne.  Hence TWh here are the oil equivalent values multiplied by 42 and divided by 3.6.
  5. Typical calculation 293 = (33.56 billion)/(128.67 million x 345.24/387.3).
  6. The BERR and others’ estimates of emissions treat the generating industry itself and sometimes the grid as end users.  That leads to lower emissions per GWh delivered than we have calculated.

Comparison with Energy Trends

Energy Trends, March 2007, provides 131 Tonnes of Carbon per GWh generated i.e. before generating industry use or transmission losses.  The electricity generated was 408,500 GWh.  The end user consumption amounted to 344.85 GWh.  Hence multiplying the carbon emission per GWh generated by the ratio 408.5/344.85 provides the carbon per GWh used by end users.  That yields 155 Tonnes which is close to the 157 Tonnes in Table A1.

 

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