Carbon monoxide emission estimates

Carbon monoxide arises from incomplete fuel-combustion and is of concern mainly because of its effect on human health and its role in tropospheric ozone formation. It leads to a decreased uptake of oxygen by the lungs and can lead to a range of symptoms as the concentration increases.

The UK emissions of carbon monoxide are shown in Figure 4.6 and Table 4.9 disaggregated by source and fuel. Over the period 1970-1999 emissions decreased by 44% reflecting significant reduction in emissions from road transport, domestic and agricultural sectors.

Figure 4.6 Time Series CO Emissions

The spatial disaggregation of CO emissions is shown in Figure 4.7. The observed pattern of emissions is clearly dominated by road transport emissions. A large proportion of road transport emissions are from vehicles travelling at slow speeds on urban or minor roads, hence the map shows high emissions in urban conurbations.

Figure 4.7 Spatially Disaggregated UK Emissions of CO

Transport

The most important source of CO is road transport and in particular petrol driven vehicles. Emissions from road transport fell only slightly between 1970 and 1990 but in recent years have declined more significantly. This is due primarily to the increased use of catalytic converters and to a lesser extent to fuel switching from petrol cars to diesel cars. The emissions from off-road sources includes portable generators, fork lift trucks, lawnmowers and cement mixers. The estimation of emissions from such machinery is very uncertain since it is based on estimates of equipment population and annual usage time.

Table 4.9 UK Emissions of Carbon Monoxide by UN/ECE1 Source Category and Fuel (kt)

1970

1980

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

1999%

BY UN/ECE CATEGORY2

Comb. in Energy Prod.

Public Power

117

121

114

113

110

100

106

104

102

71

73

61

1%

Petroleum Refining Plants

7

7

6

7

7

7

7

7

7

7

8

7

0%

Other Comb. & Trans.

45

24

22

22

20

20

20

22

23

23

26

27

1%

Comb. in Comm/Inst/Res

0%

Residential Plant

1251

622

358

382

347

369

324

260

268

246

239

252

5%

Comm/Pub/Agri Comb.

46

26

22

22

21

21

20

19

19

19

18

18

0%

Combustion in Industry

Iron & Steel Comb.

220

63

108

102

106

105

97

98

98

100

102

105

2%

Other Ind. Comb.

142

82

79

75

75

74

76

72

65

66

55

68

1%

Production Processes

367

283

442

425

410

414

431

440

455

463

470

476

10%

Extr./Distrib. of Fossil Fuels

2

2

7

3

3

2

3

3

3

3

3

1

0%

Road Transport

5427

5378

5235

5072

4855

4525

4268

4003

3961

3726

3507

3293

69%

Other Trans/Mach

Off-Road Sources

588

519

438

454

462

448

438

417

419

419

420

419

9%

Other3

28

26

27

25

24

24

22

22

23

21

19

18

0%

Waste

3

45

31

28

27

27

35

25

25

20

21

17

0%

Land Use Change

288

449

266

228

165

4

0

0

0

0

0

0

0%

By FUEL TYPE

Solid

1697

847

610

628

593

596

542

476

474

429

423

420

9%

Petroleum

6082

5945

5717

5569

5358

5014

4744

4456

4416

4176

3956

3739

79%

Gas

43

35

40

40

43

49

54

56

61

58

60

65

1%

Non-Fuel

710

820

788

719

639

481

507

503

517

522

522

535

11%

TOTAL

8531

7647

7155

6956

6633

6140

5847

5492

5468

5184

4960

4760

100%

1 UK emissions reported in IPCC format (Salway, 2001) differ slightly due to the different source categories used.

2 See Appendix 4 for definition of UN/ECE Categories

3 Including railways, shipping, naval vessels, military aircraft

Other sources

Other emission sources of CO are small compared with transport and off-road sources. Emissions from the domestic sector have decreased by 80% since 1970 due to the decline in the use of solid fuels in favour of gas and electricity. The sudden decline in emissions from the agricultural sector reflects the banning of stubble burning in 1993 in England and Wales. Currently energy production accounts for only 2% of UK emissions.