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Economy & Energy
No 25:  April-May 2001   ISSN 1518-2932

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BUSCA

CORREIO

DADOS ECONÔMICOS

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e&e ANTERIORES

e&e No 25

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Emission Parameters of Heavy Vehicles

Evaluation of heavy Vehicles Emissions

Light Vehicles Emissions

Evolution of the Brazilian Public Debt 

Application of the Emission Matrix Coefficients

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See Also: Emission Parameters of Heavy Vehicles

Evaluation of Light Vehicles Emissions 

     1 – Results of the Historical Study  

A historical study made for the period from 1970 to 1998 has permitted to evaluate some parameters concerning the behavior of the fleet and the influence of age on vehicle’s consumption. It was also possible to infer the share of gasoline whose consumption can be assigned to the heavy fleet. Since this consumption is of relatively little importance, we have opted to treat the emissions of the heavy fleet (trucks and buses) using gasoline together with Otto cycle vehicles. For the purpose of analyzing  emission by vehicle range, we will also consider emissions of diesel light vehicles and gasoline heavy vehicles.

The evaluation of the circulating and total fleet by age was object of the work presented in the previous issue of e&e. It was possible to obtain the evolution of the light and heavy fleet along the last decades. In the emission evaluation we will use values from 1970 on. The physical module that describes the fleet supplies data: by type of fuel (diesel, gasoline and alcohol), by type of vehicle (cars, light commercials, heavy commercials and buses) and by age range (1 year, 2 years, 3 to 5 years, 6 to 10 years and V Fleet that designates the old fleet that is more than 15 years old). In the case of the light fleet we are mainly interested in alcohol and gasoline vehicles. The values referring to diesel consumption in cars and light commercials were treated in chapters 4 and 5. The natural gas consumption in light vehicles and that of gasoline (and anhydrous alcohol in the mixture) in heavy vehicles were treated with the help of general emission coefficients at the end of the present chapter.

      2 Consumption Parameters  

The consumption of vehicles within the same range varies according to the manufacturing year and age. The first factor refers to innovation and model profiles sold in each year. The use of the vehicles, in terms of kilometers annually traveled, varies according to the vehicle’s age since older vehicles are generally in the hands of people with smaller purchase power who use them less. In a country like Brazil, where the number of vehicles is not known, one cannot expect to have precise data about specific consumption and emission by manufacturing year and fleet’s age.

As it is clear in our historical and prospective study (MCT/PNUD report), previously mentioned, these data were tentatively extracted from global data and took advantage of the strong variation in the fleet’s composition. In the present study we have tried to introduce consumption values as a function of the vehicles’ age range. In the above mentioned report, the historical data permit to evaluate consumption as a function of the average age because of  the variation of age in the alcohol car fleet, introduced in the market from 1979 on, and that of gasoline cars that aged during the period when sales of alcohol cars were predominant, followed by their rejuvenation with the return to the predominance of light gasoline vehicles.

When reliable parameters are available, the problem can be treated using for each manufacturing year a specific consumption by traveled kilometer, as a function of the vehicle’s age, multiplied by the distance annually traveled, as a function of the vehicle’s age.

We consider that this treatment introduces a refining that would be incoherent vis-à-vis the uncertainty of the existing data. This fact led us to suggest a treatment that is slightest different from the usual one but that can be a posteriori inferred.

The light fleet – cars and light commercial vehicles – was treated in an homogeneous way. It is known that the permitted tonnage for the so called light commercial vehicles of the Otto cycle has limited its real commercial use. Since it has not a very high specific consumption and its participation in the light fleet is about 10% (1994 values), it seemed that it would be not useful to treat it separately. However, it was considered that its consumption is equivalent to that of two cars manufactured in the same.

The consumption variation with age was considered as a function of the average age when treating historical data. The consumption was assumed to decrease in a linear way from the moment of purchase on until reaching the minimum value of 0.5 tep in equivalent energy gasoline (or NG). This value is coherent with what was observed for the gasoline fleet in the 13-year-old  range (average), as the historical study has shown.

The consumption was supposed to vary according to a straight line [c = a.t + b] where a is negative (function decreasing with time) and b is the initial consumption level. The inferior value of c was limited to 0.5. We have varied these parameters in order to better reproduce the consumption curve along the years. The value of a=- 0.1, corresponding to fitting for alcohol, was considered the same for gasoline and alcohol vehicles and the value of b was adjusted for each fuel.  

Figures 1 and 2 show the adjustment obtained for the consumption, when the fleet was considered by age for gasoline and alcohol vehicles.

Figure 1: Alcohol consumption  of the lasting fleet and consumption curve by age shown in 3

 
Figure 2: Comparison between the verified and calculated consumption of the so called gasoline vehicles (gasoline + anhydrous alcohol) from the estimated fleet and from the consumption curve by age shown in 3.

Figure 3: Consumption curve by age and values used by age range.

The reproduction of alcohol consumption verified and even that of gasoline, from adjustment of parameters, is really acceptable, considering that in the adjustment there isn’t any hypothesis concerning consumption variation as a function of fuel prices and vehicles’ technical evolution. Only the larger alcohol fleet consumption is explained by the policy maintained along the years, namely favoring the price of the traveled kilometer using this fuel.  

As in the last years this difference had been reduced, the gasoline cars were destined to more intensive use such as taxi and service fleets, what would explain a consumption larger than the calculated one for the last years.

The adjustment is useful for defining the consumption by  different age ranges since with aging of the vehicle the emission conditions are also modified. This profile consumption as a function of age is used as the real consumption of each year for emission evaluation.

3 – Emissions Generating the Greenhouse Effect

For new vehicles, the emission factors applied for gasoline (fuel mixture with 22% anhydrous alcohol in volume) were based on CETESB’s data presented in Table 1. For evaporation, the adopted data were based on American cars of the previous generation. These data were adopted in the Brazilian Inventory of Greenhouse Effect Gases in its present edition [1], available at http://www.mct.gov.br.

In what follows, some comparisons will be made between the results of the present work – elaborated together with that for  prospective ends – and those of the previous work (COLOCAR O NOME DO TRABALHO) that aimed at evaluating the inventory of emissions between 1990 and 1994.

In Table 1 are presented emission data for new vehicles in g/km. In order to be used in the present work they were converted to carbon values. Table 1 contains implicitly the consumption by the assumed km for each manufacturing year.

Table 1 – Emissions for New Vehicles – Gasohol (22% anhydrous alcohol in volume)

 

CO

HC

CH4

NOx

C02

Evapora.

C

Gasool(*)

Vol/Dist

Dist/Vol

 

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(ml/km)

(km/l)

pré-80

54

4,7

0,94

1,2

174,72

4,3

74,9

97,6

130,5

7,7

80-83

33

3

0,6

1,4

174,72

4,3

64,4

83,9

112,3

8,9

84-85

28

2,4

0,48

1,6

174,72

4,3

61,7

80,4

107,6

9,3

86-87

22

2

0,4

1,9

174,72

4,3

58,8

76,6

102,5

9,8

88

18,5

1,7

0,34

1,8

174,72

4,3

57,1

74,3

99,5

10,1

89

15,2

1,6

0,32

1,6

174,72

4,3

55,6

72,4

96,9

10,3

90

13,3

1,4

0,28

1,4

177,11

0,43

55,2

72,0

96,3

10,4

91

11,5

1,3

0,26

1,3

178,7

0,43

54,8

71,4

95,5

10,5

92

6,2

0,6

0,12

0,6

193,4

0,32

55,9

72,9

97,5

10,3

93

6,3

0,6

0,12

0,8

193,4

0,32

56,0

72,9

97,6

10,2

94

6

0,6

0,12

0,7

193,4

0,32

55,8

72,8

97,3

10,3

95

4,7

0,6

0,12

0,6

206,9

0,32

59,0

76,8

102,8

9,7

 (*) 22% anhydrous alcohol 76,75% of mass is C and specific mass of 0,7474 kg/liter

In the following Table 2 data is presented as a function of emitted carbon, what will ease our calculations.

Table 2 – Mass of gases emitted by one unit of carbon mass contained (gasohol)

CO

HC-met.

CH4

NOx

C02

Evaporativas

0,7211

0,0502

0,0126

0,0160

2,3333

0,0574

0,5124

0,0373

0,0093

0,0217

2,7129

0,0668

0,4535

0,0311

0,0078

0,0259

2,8300

0,0696

0,3740

0,0272

0,0068

0,0323

2,9705

0,0731

0,3242

0,0238

0,0060

0,0315

3,0622

0,0754

0,2736

0,0230

0,0058

0,0288

3,1449

0,0774

0,2409

0,0203

0,0051

0,0254

3,2073

0,0078

0,2099

0,0190

0,0047

0,0237

3,2612

0,0078

0,1109

0,0086

0,0021

0,0107

3,4582

0,0057

0,1126

0,0086

0,0021

0,0143

3,4556

0,0057

0,1075

0,0086

0,0021

0,0125

3,4636

0,0057

0,0797

0,0081

0,0020

0,0102

3,5090

0,0054

In tables 3 and 4 the corresponding values for hydrated alcohol are shown

Table 3 – Emissions for New Vehicles– Hydrated Alcohol  

 

CO

HC-met

CH4

NOx

C02

Evaporativas

C

Álcool Hidr.

 

 

 

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(g/km)

(ml/km)

(km/l)

80-83

18

0,96

0,64

1

174,7

1,8

56,7

108,6

134,3

7,4

84-85

16,9

0,96

0,64

1,2

174,7

1,8

56,2

107,7

133,2

7,5

86-87

16

0,96

0,64

1,8

174,7

1,8

55,8

107,0

132,3

7,6

88

13,3

1,02

0,68

1,4

174,7

1,8

54,7

104,9

129,7

7,7

89

12,8

0,96

0,64

1,1

164,2

1,8

51,6

98,9

122,2

8,2

90

10,8

0,78

0,52

1,2

163,6

0,29

50,3

96,5

119,2

8,4

91

8,4

0,66

0,44

1

163,1

0,29

49,0

93,9

116,1

8,6

92

3,6

0,36

0,24

0,5

165,6

0,14

47,2

90,5

111,8

8,9

93

4,2

0,42

0,28

0,6

165,6

0,14

47,5

91,1

112,6

8,9

94

4,6

0,42

0,28

0,7

165,6

0,14

47,7

91,4

113,0

8,8

95

4,6

0,42

0,28

0,7

164,9

0,14

47,5

91,1

112,6

8,9

Table 4 - Mass of emitted gases as a function of carbon mass contained (hydrated alcohol)

 

CO

HC

CH4

NOx

C02

Evaporativas

80-83

0,3176

0,0169

0,0113

0,0176

3,0826

0,0318

84-85

0,3007

0,0171

0,0114

0,0213

3,1084

0,0320

86-87

0,2866

0,0172

0,0115

0,0322

3,1299

0,0322

88

0,2429

0,0186

0,0124

0,0256

3,1914

0,0329

89

0,2482

0,0186

0,0124

0,0213

3,1832

0,0349

90

0,2146

0,0155

0,0103

0,0238

3,2516

0,0058

91

0,1715

0,0135

0,0090

0,0204

3,3295

0,0059

92

0,0763

0,0076

0,0051

0,0106

3,5085

0,0030

93

0,0883

0,0088

0,0059

0,0126

3,4835

0,0029

94

0,0964

0,0088

0,0059

0,0147

3,4709

0,0029

95

0,0968

0,0088

0,0059

0,0147

3,4702

0,0029

5 – Emissions in the 1990-1997 Period

The general treatment applied to the data permits to obtain results for the whole 1990-1997 period and they will be presented in the annexed tables 6A 1 to 3. The values of annual fuel consumption were distributed among the vehicles so that there would be the same consumption proportion by age range as those calculated. In Table 5 we compare the fleet of the present work with that considered in the Inventory. The fleet of the present work is 20% higher than that of the Inventory. As we have already commented, Brazilian statistics concerning the fleet are precarious. Our fleet was adjusted so that it would reproduce the amount and average age of DENATRAN’s statistics quoted by  ANFAVEA in (R8). They practically coincide with the total fleet for the last years used by ANFAVEA. The mentioned discrepancies found when calculating emissions are adjusted in order to reproduce the consumption values.

Table 5 – Light Vehicle Fleet (thousand vehicles Inventory (R11)        

 

Gasoline

Alcohol

Total

Total

 

Automóveis

Com. Leves

Automóveis

Com. Leves

Automóveis

Com. Leves

Geral

1990

7085

811

3941

454

11026

1265

12290

1991

7279

832

4001

458

11280

1290

12570

1992

7437

846

4104

471

11540

1318

12858

1993

7678

871

4248

491

11926

1362

13288

1994

8189

931

4362

504

12551

1435

13986

1995

9032

1052

4368

502

13400

1554

14954

Cars

 Light Com

 General

Present work

Este Trabalho

 

Gasoline

Alcohol 

Total

Total

 

Automóveis

Com. Leves

Automóveis

Com. Leves

Automóveis

Com. Leves

Geral

1990

5724

741

3442

417

9166

1158

10324

1991

5807

762

3481

425

9288

1187

10475

1992

5860

773

3538

440

9398

1213

10611

1993

6458

808

3639

459

10097

1267

11364

1994

6795

873

3615

461

10410

1334

11744

1995

7788

1001

3490

446

11278

1447

12725

               

Cars

Light Com.

 General

Comparison between the two works (our values=100)     

 

Gasoline

Alcohol

Total

Total

 

Automóveis

Com. Leves

Automóveis

Com. Leves

Automóveis

Com. Leves

Geral

1990

124

109

114

109

120

109

119

1991

125

109

115

108

121

109

120

1992

127

109

116

107

123

109

121

1993

119

108

117

107

118

107

117

1994

121

107

121

109

121

108

119

1995

116

105

125

112

119

107

118

 Cars

Light Com.

 General

The emission values are shown in Table 6

In the emissions it was considered :

·        Estimated fleet in the age ranges,

·        Consumption corresponding to this fleet, considering the consumption of the new vehicle in the year of origin and the age of the vehicle,

·        Re-normalized consumption so that it reproduces the Otto cycle demand for light vehicles,

·        Evaluation of emission levels degradation for hydrocarbons (including methane) and carbon monoxide[2];.

·        Determination of emission in carbon from the carbon mass by kg of fuel,·

·        Determination of emission in the initial year according to Tables 2 and 4,·

Propagation of emissions in the year of sale of the vehicle for each age range (weighted average of values, according to the case)

·        Evaluation of the aging effect by age range for CO and HC, and  

·        Determination of emissions by fuel and by polluting gas

· Table 6 – Emissions by Light Vehicles  (thousand t/year)

Gasoline (pure) 

 

CO

HC

NOx

CH4

CO2

Evap

1990

3296

225

83

56

9345

273

1991

3322

229

98

57

11412

248

1992

3125

218

105

55

12400

229

1993

2974

207

103

52

14142

235

1994

2874

201

112

50

17010

220

1995

2983

210

125

52

22198

199

1996

3128

221

140

55

27526

216

1997

3090

218

149

55

31622

216

Anhydrous Alcohol (in mixture)

 

CO

HC

NOx

CH4

CO2*

Evap

1990

406

28

10

7

1191

34

1991

511

35

15

9

1799

38

1992

652

46

22

11

2643

48

1993

644

45

22

11

3123

51

1994

732

51

29

13

4396

56

1995

684

48

29

12

5142

46

1996

736

52

33

13

6539

51

1997

823

58

40

15

8487

58

Fuel Mixture (gasohol) 

 

CO

HC

NOx

CH4

CO2+CO2*

Evap

1990

3702

252

94

63

10536

306

1991

3833

265

113

66

13211

286

1992

3777

264

126

66

15043

276

1993

3618

252

125

63

17265

286

1994

3606

252

141

63

21406

276

1995

3667

258

154

65

27340

245

1996

3864

273

173

68

34065

267

1997

3913

276

188

69

40110

274

Hydrated Alcohol

 

CO

HC

NOx

CH4

CO2*

Evap

1990

1241

77

98

51

12052

116

1991

1259

77

91

51

12082

112

1992

1117

68

75

45

11147

95

1993

1099

66

76

44

11614

86

1994

1082

65

76

43

11771

85

1995

1124

68

79

45

11934

96

1996

1076

66

79

44

11801

89

1997

907

57

69

38

10029

72

                          Total             

 

CO

HC

NOx

CH4

CO2+CO2*

Evap

1990

4942

329

192

114

22588

422

1991

5092

342

204

118

25293

398

1992

4894

332

202

111

26190

371

1993

4718

318

201

107

28879

372

1994

4687

317

217

106

33177

361

1995

4791

326

233

110

39274

341

1996

4940

339

251

112

45866

355

1997

4819

333

257

107

50138

346

 

38883

2635

1758

885

271406

2967

                                                                     

 (*) The CO2 emitted by biomass is annulled in the production from the point of view of the greenhouse effect . From the cumulative point of view, the same procedure should be adopted for CO.  

The results of the present work concerning emissions are not far from the expected one for hydrated alcohol. Actually the specific consumption adjustment compensates the superior value of the fleet. There are significant differences referring to fuel mixture or gasohol. Apparently these differences are due to the criterion adopted, namely  considering the CO2 emissions as the total conversion of the carbon contained in the fuel. Analysis of these differences are made in the annex.

6 – Variation in the Mixture

Emissions from fuel mixtures vary according to their composition. The correct consideration of this variation would nevertheless demand analysis of the effect on these emissions.. It has been reported that the worse the emission conditions are, the effects on CO emission  would be more positive in percent terms. This fact does not seem to be reflected in the table used as reference.  

The variation in the fuel mixtures are shown in Figure 4.

 
Figure 4: Variation of anhydrous alcohol in the mixture (national average)

In the period examined by the present work, 1990/1997, there was considerable change in the mixture, mainly in the two last years. In our calculation process, the division between anhydrous alcohol and gasoline is carried out automatically.

7- Emissions by Age of Fleet 

 The adopted procedure permits to identify the age range from where the emission comes, by type of emission. The process allows to easily change this range. The evaluation was made year by year between 1990 and 1998. The corresponding tables are Tables 6 A 4, 5 and 6.

In Figure 5 the evolution of CO2 emissions from gasoline by age range is shown (not including those due to anhydrous alcohol which should not be accounted for because they originate from biomass).

 

Figure 5: Emissions from the gasoline light fleet by age range

Figure 6 shows the dramatic changes in emissions resulting from modifications in the fleet.

 

Figure 7: Emissions from vehicles that were more than 5 years old were responsible for almost 90% of emissions in 1988.

8 - Avoided Emissions 

Emissions that were prevented due to substitution and displacement that occurred in the country’s fleet in the past but whose effects last until now should consider at least three factors:

·        The presence of anhydrous and hydrated alcohol,

·        Displacement of gasoline by diesel (of larger efficiency) and

·        Improvement in efficiency of engines.

We will try to evaluate the first two factors.

The use of useful energy permits to treat in a clear and simple way the substitution process without confounding it with a general improvement in efficiency which would be the third factor that affects the group of fuels.

 

Table 7:Avoided Emissions

Real Emissions

 

CO

CO*

HC

NOx

CH4

CO2

Evap

1990

3296

1647

329

192

114

9345

273

1991

3322

1770

342

204

118

11412

248

1992

3125

1769

332

202

111

12400

229

1993

2974

1744

318

201

107

14142

235

1994

2874

1813

317

217

106

17010

220

1995

2983

1808

326

233

110

22198

199

1996

3128

1812

339

251

112

27526

216

1997

3090

1729

333

257

107

31622

216

 

Emissions Using Gasoline

 

CO

CO*

HC

NOx

CH4

CO2

Evap

1990

7913

 

540

200

135

22439

655

1991

7616

 

526

225

131

26163

569

1992

6937

 

485

232

121

27522

507

1993

6492

 

452

225

113

30868

513

1994

6085

 

426

238

107

36012

466

1995

5795

 

408

243

102

43124

387

1996

5694

 

402

255

101

50112

393

1997

5285

 

373

254

93

54083

370

Avoided Emissions

 

CO

CO*

HC

NOx

CH4

CO2

Evap

1990

2971

1647

211

9

21

13094

382

1991

2524

1770

184

21

14

14751

321

1992

2043

1769

153

31

10

15122

279

1993

1774

1744

134

24

6

16726

278

1994

1397

1813

109

21

0

19002

246

1995

1004

1808

82

10

-8

20926

188

1996

754

1812

63

3

-12

22587

177

1997

465

1729

40

-3

-14

22460

153

Avoided Emissions (percent relative to gasoline)

 

CO

CO*

HC

NOx

CH4

CO2

Evap

1990

38%

21%

39%

4%

15%

58%

58%

1991

33%

23%

35%

9%

11%

56%

56%

1992

29%

25%

32%

13%

8%

55%

55%

1993

27%

27%

30%

11%

5%

54%

54%

1994

23%

30%

26%

9%

0%

53%

53%

1995

17%

31%

20%

4%

-7%

49%

49%

1996

13%

32%

16%

1%

-12%

45%

45%

1997

9%

33%

11%

-1%

-15%

42%

42%

The avoided emissions (average in the period) are summarized in the substitution table. The substitution of one tep of gasoline (equivalent) by anhydrous alcohol in the mixture produced a reduction of 2.26 t of CO2 in the emission. The effects of adding anhydrous alcohol for reduction of emissions were not calculated for other gases since emission from gasoline was considered as being the same as that of fuel mixture. Tests carried out in Brazil, the United States and Japan verified a reduction of CO and HC emission and increase of NOx and CH4. Normally, the beneficial effects are larger than the negative ones. In a general way,  mixture reduction for cars adjusted to use it has negative effects on the performance and emissions.

The substitution of one tep of gasoline by hydrated alcohol produced on the average a reduction of 2.13 t of CO2, 0.24 t of CO and practically negligible results for the other gases.

In the 1997 conditions , the effects of better yields in gasoline vehicles, reduction of improvements in alcohol vehicles and mainly the aging of the fleet made the effects of substitution less significant.

In Table 8 we have also marked the carbon emissions in the form of CO* that represent material of organic nature that once completely oxidized interrupt their effects on the environment. The alternative is to consider the CO2 credit in biomass production and the debit in CO.

REFERENCES

(1)   Um Modelo econométrico para Demanda de Gasolina pelos Automóveis de Passeio Ricardo Paes de Barros e Silvério Soares Ferreira IPEA - May 1992 - 135 pag

(2) Estatísticas Históricas do Brasil  IBGE 1987 - Volume 3

(3) Últimos anos GEIPOT e ANFAVEA - Anuário Estatístico / Statistical Yearbook   1998 (Internet) 

See Also: Emission Parameters of Heavy Vehicles and
Evaluation of heavy Vehicles Emissions