Net Energy Use and Energy Substitution Efficiency

The energy substitution efficiency (ESE) was calculated for a number of the options investigated in this study. The calculations show the effect of allocation methods as well as fuel blends and vehicle/fuel performance on the WtW net energy use and the energy sub­stitution efficiency. The results are given in Table 6 and illustrated in Figure 6.

Allocation LUC

Fuel

WtT

(MJp/MJth)

TtW

(MJth/km)

WtW

(MJp/km)

Index

(-)

Energy

substitution

efficiency

REF

REF

Gasoline

1.362

X

2.564

= 3.493

100.0

A-1

LUC-1

E5-1

0.401

X

1.413

= 0.567

16.2

69.6%

A-2

LUC-1

E5-1

0.758

X

1.413

= 1.071

30.7

57.6%

A-3

LUC-1

E5-1

0.405

X

1.413

= 0.573

16.4

69.5%

A-4

LUC-1

E5-1

0.359

X

1.413

= 0.493

14.1

71.4%

S-1

LUC-1

E5-1

1.281

X

1.413

= 1.810

51.8

40.0%

S-2

LUC-1

E5-1

-0.220

X

1.413

= -0.310

-8.9

90.5%

S-3

LUC-1

E5-1

0.450

X

1.413

= 0.636

18.2

68.0%

S-4

LUC-1

E5-1

-1.051

X

1.413

= -1.485

-42.5

118.4%

A-1

LUC-1

E5-1

0.401

X

1.413

= 0.567

16.2

69.6%

A-1

LUC-1

E10-1

0.401

X

1.174

= 0.471

13.5

86.5%

A-1

LUC-1

E85-1

0.401

X

2.485

= 0.997

28.5

33.8%

A-1

LUC-1

E-2

0.401

X

1.703

= 0.684

19.6

55.4%

A-1

LUC-1

E-3

0.401

X

2.564

= 1.029

29.5

32.3%

TABLE 6 WtW Net NonRenewable Primary Energy Use and Energy Substitution Efficiency of Ethanol according to Selected Options

Allocation

LUC

Fuel

Energy

Index

Gasoline

100.0

A-1

LUC-1

Bioethanol,

as E5

E5-1

16.2

A-2

LUC-1

Bioethanol,

as E5

E5-1

30.7

A-3

LUC-1

Bioethanol,

as E5

E5-1

16.4

A-4

LUC-1

Bioethanol,

as E5

E5-1

14.1

S-1

LUC-1

Bioethanol,

as E5

E5-1

51.8

S-2

LUC-1

Bioethanol,

as E5

E5-1

-8.9

S-3

LUC-1

Bioethanol,

as E5

E5-1

18.2

S-4

LUC-1

Bioethanol,

as E5

E5-1

-42.5

A-1

LUC-1

Bioethanol,

as E5

E5-1

16.2

A-1

LUC-1

Bioethanol,

as E10

E10-1

13.5

A-1

LUC-1

Bioethanol,

as E85

E85-1

28.5

A-1

LUC-1

Bioethanol

E-2

19.6

A-1

LUC-1

Bioethanol

E-3

29.5

Подпись: Index base 100 for gasoline -60 -40 -20 0 20 40 60 80 100 120

FIGURE 6 WtW net non-renewable primary energy use of ethanol according to selected options.

The results indicate that the choice of the allocation method has a significant impact on the WtW net energy use, with values ranging from -1.485 MJp/km (S-4, i. e., substitution with both straw and DDGS as fuel) to 1.810 MJp/km (S-1, i. e., substitution with both straw and DDGS as animal feed), that is, from -143% to -48% with respect to gasoline, with E5-1 as the option regarding fuels blend and vehicle/fuel performance. The effect of the fuel blend and vehi — cle/fuel performance is also significant, with net energy uses ranging from 0.471 MJp/km (E10-1, i. e., ethanol used as E10 based on actual test data) to 1.029 MJp/km (E-3, i. e., energy basis), that is, from -86% to -70% with respect to gasoline, respectively.

Both these methodological choices also significantly affect the energy substitution effi­ciency (ESE). For a given fuel blend and vehicle/fuel performance, the higher the nonrenew­able primary energy use, the lower the ESE. For a given allocation method and bioethanol production pathway, the ESE is best when bioethanol is used in the form of E10. This notion is particularly useful when considering a given volume of bioethanol (at the scale of a country or a region for example). The results show how much more efficient it is to use this volume of bioethanol as E10 than to use it as E85 or even E5, for a given service (i. e., a given overall dis­tance traveled). The situation is obviously different when considering a vehicle owner traveling a given distance every year. The best choice (in terms of both energy and GHG bal­ance) for a specific consumer is obviously to use E85 (with a maximum volume of gasoline displaced), as long as the net energy use or net GHG emissions of the biofuel are better than those of gasoline.