1
Supporting Information:
2
Uncertainty analysis of the environmental
3
sustainability of biofuels
4
Stephan Pfister1*, Laura Scherer1
5
1
ETH Zurich, Institute of Environmental Engineering, Schafmattstrasse 6, 8093 Zurich,
6
Switzerland
7
*Corresponding author e-mail: pfister@ifu.baug.ethz.ch; phone: +41 44 633 75 71
8
1
9
10
S1. Abbreviations
Table S1: List of abbreviations
bg_agri
bg_biowaste
bg_grass
bg_sewage
bg_whey
CF
CTV
CV
GHG
GM
GWP20, GWP100,
GWP500
k
LCA
LMC
vkm
PMC
R-EQ
R-HH
R-RS
R-TT
WSFP
WSI
Biogas, from agricultural digestion, not covered, at storage
Biogas, from biowaste, at storage
Biogas, from grass, digestion, at storage
Biogas, from sewage sludge, at storage
Biogas, from whey, digestion, at storage
Characterization factor (impact assessment)
contribution to variance
Coefficient of variation
greenhouse gas
geometric mean
Global warming potential for the 20, 100 and 500 years, respectively
k-value for uncertainty assessment based on Slob (1994)
Life Cycle Assessment
Monte Carlo simulations with Latin hypercube sampling
vehicle-kilometer (transport unit)
primitive Monte Carlo simulations
ReCiPe (H/A) endpoint results for ecosystem quality impacts
ReCiPe (H/A) endpoint results for human health impacts
ReCiPe (H/A) endpoint results for resources impacts
ReCiPe (H/A) endpoint results for total impacts
water scarcity footprint
water stress index (CF for water consumption)
11
12
2
13
S2. System description (example of most important flows and processes for
14
“biogas” and “natgas”
15
16
17
18
19
Figure S1: System description (processes and flows) for the “natgas” transport case. Most important processes and
flows identified for GWP100 are selected and presented based on their level in the product system (e.g. level 5 is an
input to level 4 etc.). Results extracted from the Aveny LCA tool (Aveny GmbH 2011).
3
20
21
22
23
Figure S2: System description (processes and flows) for the “biogas” transport case. Most important processes and
flows identified for GWP100 are selected and presented based on their level in the product system (e.g. level 5 is an
input to level 4 etc.). Results extracted from the Aveny LCA tool (Aveny GmbH 2011).
24
25
26
4
27
S3. Partial uncertainty assessment
28
Table S2 shows the probabilities if only part of the uncertainty is analyzed. For the liquid fuels decision
29
uncertainty is mainly caused by emission factors for GWP, and basically no uncertainty exists for WSFP.
30
For gas alternatives, the result decision uncertainty is affected by all three uncertainties for the GWP20,
31
while it is robust (>90% chance) for the GWP500.
32
33
34
Table S2Probabilities that biofuel is the better option compared to its fossil alternative, considering: (1)
uncertainties in impact assessment, only, (2) uncertainties in impact assessment and emission factors, only, or (3)
all uncertainties (including process activity)
Case
Diesel - biodiesel
petrol - biopetrol
natgas - biogas
natgas - bg_agri
natgas - bg_biowaste
natgas - bg_sewage
natgas - bg_grass
natgas - bg_whey
GWP 20a
100
80.5
79
0
47
47
1
7
14
0
1
2
0
4
5
37
38
47
1
5
23
5
15
32
GWP 100a
100
78.2
78
0
49
48
94
86
82
63
62
60
63
64
63
100
100
95
76
59
58
99
90
80
35
36
5
GWP 500a
100
85.5
85
0
49
49
100
100
100
100
100
100
100
99
99
100
100
100
100
98
92
100
100
98
WDF total
0
0
0
0
0
0
66
72
65
47
55
52
67
72
66
66
71
66
4
12
13
25
40
37
Level
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
37
S4. CTV results
38
Table S3 shows the CTV results for GWP and Table S4 shows CTV results for WSFP. While the CTV_all
39
for GWP is not robust, for WFSP we see that 97% of CTV is related to process activities, and 2.5% to
40
emission factors.
6
41
Table S3: CTV results for carbon footprint of the “biogas vs. natural gas” comparison. Only the top 50 CTV results are reported in each assessment.
CTV_all
Flow
Process
Biogas, from
biowaste, at
storage
Biogas, from
sewage sludge, at
st
Methane, 96 vol%, from biogas, a
Methane, 96 vol%, from biogas, h
Disposal,
municipal solid
waste,
Methane, 96 vol%, from biogas, p
Natural gas,
burned in boiler
atm
Electricity, at
cogen with biogas
Crude oil, at
production
onshore
Disposal, plastics,
mixture, 15.3
Methane, 96 vol%, from biogas, l
Natural gas, high
pressure, at co
Crude oil, at
production
Refinery gas, at
refinery
Disposal, refinery
CTV_B
CTV
[%]
St
ag
e
Flow
process
x
Dinitrogen
monoxide
Potatoes IP, at far
Methane,
biogenic
Electricity, at c
Dinitrogen
monoxide
Hard coal, burned
i
Methane, fossil
Bitumen, at ref
0.38
x
0.37
x
0.36
x
Methane, dichloro-,
HCC-30
0.51
Methane, 96 vol-%, from biogas, at
purification
0.38
Carbon monoxide,
fossil
4.60
Ethane, hexafluoro-,
HFC-116
0.51
Methane, 96 vol-%, from biogas, high
pressure, at consumer
0.37
0.43
Disposal, municipal solid waste, 22.9%
water, to municipal incineration
0.36
Treatment, cera
x
Carbon dioxide,
fossil
Copper, primary,
at re
0.37
Carbon dioxide,
fossil
Agricultural
machinery
0.35
Methane, fossil
Hard coal, burn
0.42
0.38
0.38
0.32
x
0.32
x
0.32
0.35
x
Methane, fossil
Disposal, plast
0.32
0.33
x
0.32
x
0.31
x
Carbon dioxide,
fossil
Dinitrogen
monoxide
Disposal,
polyvinylchl
Hard coal, burned
i
Chloroform
Trifluorom
Methane, bromo-,
Halon 1001
3.27
Methane, fossil
0.32
19.0
2
Carbon dioxide, land
transformation
x
0.33
Carbon dioxide, fossil
0.40
Flow
0.39
Hard coal, burned
in p
Solid unbleached
board
x
CTV_C
CTV
[%]
Biogas, from sewage sludge, at
storage
Carbon dioxide,
fossil
Carbon dioxide,
fossil
x
Flow
0.53
Harvesting, by
complet
0.34
CTV_y
CTV
[%]
Biogas, from biowaste, at storage
Carbon dioxide,
fossil
0.35
Process
0.57
0.35
x
CTV_x
CTV
[%]
Methane, 96 vol-%, from biogas,
production mix, at service station
Natural gas, burned in boiler atm.
low-NOx condensing non-modulating
<100kW
Electricity, at cogen with biogas
engine, allocation exergy
Crude oil, at production onshore
Chloroform
Dinitrogen monoxide
0.35
0.35
0.34
0.33
Disposal, plastics, mixture, 15.3%
water, to municipal incineration
Methane, 96 vol-%, from biogas, low
pressure, at consumer
Natural gas, high pressure, at
consumer
0.33
0.33
0.33
Refinery gas, at refinery
0.32
0.32
Disposal, refinery sludge, 89.5%
7
8.91
Ethane, 1,1,1,2tetrafluoro-, HFC-134a
Ethane, 1,1,2-trichloro1,2,2-trifluoro-, CFC113
Ethane, 1,1-difluoro-,
HFC-152a
Ethane, 1,2-dichloro1,1,2,2-tetrafluoro-,
CFC-114
Ethane, 2-chloro1,1,1,2-tetrafluoro-,
HCFC-124
Ethane, hexafluoro-,
HFC-116
Methane, biogenic
0.33
Crude oil, at production
0.32
2.93
4.98
1.01
1.02
0.02
1.84
0.79
1.40
14.2
3
12.9
6
10.3
0
9.48
6.25
5.66
Ethane, 1,2-dichloro1,1,2,2-tetrafluoro-,
CFC-114
Nitrogen fluoride
1.61
15.8
9
Methane, bromo-,
Halon 1001
Methane,
bromochlorodifluoro-,
Halon 1211
Methane,
Methane,
bromotrifluoro-, Halon
1301
Ethane,
chloropentafluoro-,
CFC-115
Sulfur hexafluoride
CTV
[%]
5.05
3.85
Methane, difluoro-,
HFC-32
Ethane, 2,2-dichloro1,1,1-trifluoro-, HCFC123
Methane,
chlorotrifluoro-, CFC-13
Methane, tetrafluoro-,
R-14
Methane,
trichlorofluoro-, CFC-11
Ethane, 1,1-difluoro-,
HFC-152a
Methane, trifluoro-,
3.38
3.23
3.16
2.83
2.73
2.55
sludge, 89.5%
Crude oil, at
production
onshore
Crude oil, at
production
onshore
Crude oil,
production GB, at
long
Refinery gas,
burned in furnace
Crude oil,
production RAF,
at lon
Crude oil,
production NL, at
long
Crude oil, at
production
offshore
Crude oil,
production RLA,
at lon
Crude oil, at
production
offshore
Crude oil, at
production
offshore
Crude oil,
production NO, at
long
Crude oil, at
production
onshore
Crude oil,
production RU, at
long
Crude oil,
production NG, at
long
Crude oil,
production RME,
at lon
0.31
0.31
x
Methane, fossil
Hard coal coke,
0.31
0.31
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
x
0.30
water, to hazardous waste
incineration
Crude oil, at production onshore
0.32
0.32
Carbon dioxide,
fossil
Methyl acetate, at
pla
0.31
Crude oil, at production onshore
Carbon dioxide,
fossil
Benzaldehyde, at
plant
0.30
Dinitrogen
monoxide
Disposal,
polyureth
0.30
Carbon
monoxide, fossil
Disposal, lead in
car s
0.29
Crude oil, production RAF, at long
distance transport
0.32
Methane,
biogenic
Treatment,
plywoo
0.29
Crude oil, production NL, at long
distance transport
0.32
Carbon dioxide,
fossil
Operation,
aircraft, f
0.29
Carbon dioxide,
fossil
Operation,
passenger c
0.29
Dinitrogen
monoxide
Hard coal, burned
i
0.28
Carbon dioxide,
fossil
Steel, converter,
chro
0.28
Carbon dioxide,
fossil
3-methyl-1butanol, at
0.27
Dinitrogen
monoxide
Disposal, paper, 11
Carbon dioxide,
fossil
Benzal chloride, at
pl
0.27
Crude oil, production RU, at long
distance transport
0.31
Carbon dioxide,
fossil
Natural gas, high
pres
0.27
Crude oil, production NG, at long
distance transport
0.31
Carbon dioxide,
fossil
Corrugated board
base
0.27
Crude oil, production RME, at long
distance transport
0.31
0.32
Crude oil, production GB, at long
distance transport
Ethane, 1-chloro-1,1difluoro-, HCFC-142b
2.08
3.13
Ethane, pentafluoro-,
HFC-125
1.67
1.10
Methane, monochloro, R-40
2.65
Ethane, 1,1,1,2tetrafluoro-, HFC-134a
1.05
0.32
Methane, tetrachloro-,
R-10
2.95
0.32
Methane, tetrafluoro-,
R-14
3.35
0.31
Methane,
trichlorofluoro-, CFC-11
0.97
0.31
Methane, trifluoro-,
HFC-23
0.87
Crude oil, at production offshore
2.68
Nitrogen fluoride
0.31
Crude oil, at production onshore
Methane,
dichlorofluoro-, HCFC21
Methane, tetrachloro-,
R-10
Methane,
dichlorodifluoro-, CFC12
Ethane, 1,1,1-trifluoro-,
HFC-143a
1.38
1.24
0.78
0.73
0.55
0.52
Dinitrogen monoxide
0.00
Sulfur hexafluoride
0.31
8
2.77
Methane,
chlorotrifluoro-, CFC-13
Crude oil, at production offshore
0.27
2.17
3.49
Crude oil, at production offshore
Crude oil, production NO, at long
distance transport
HFC-23
0.99
0.32
Methane,
dichlorodifluoro-, CFC12
Methane,
dichlorofluoro-, HCFC21
Methane, fossil
4.82
Methane,
bromochlorodifluoro-,
Halon 1211
Carbon monoxide,
fossil
0.32
Refinery gas, burned in furnace
Crude oil, production RLA, at long
distance transport
bromotrifluoro-, Halon
1301
Methane,
chlorodifluoro-, HCFC22
Methane, dichloro-,
HCC-30
4.03
0.32
Methane, monochloro, R-40
0.18
Carbon dioxide, fossil
0.14
Chloroform
0.13
Ethane, 2-chloro1,1,1,2-tetrafluoro-,
HCFC-124
0.11
Heavy fuel oil,
burned in refiner
Disposal, refinery
sludge, 89.5%
Naphtha, at
refinery
Natural gas,
burned in boiler
con
Electricity, low
voltage, at grid
Heat, at cogen
with biogas
engine
Heavy fuel oil,
burned in refiner
Diesel, at refinery
x
Carbon dioxide,
fossil
Carbon dioxide,
fossil
Sulphate pulp,
unbleac
Copper, primary,
at re
Carbon dioxide,
fossil
Ethane, 1,1,1,2tetrafluoro-, HFC134a
Methane,
chlorodifluoro-,
HCFC-22
Carbon dioxide,
fossil
Disposal, emulsion
pai
Uranium, enriched
4.0%, at TENEX
enric
Tetrafluoroethylen
e, at plant
Dinitrogen
monoxide
Carbon dioxide,
fossil
Carbon dioxide,
fossil
Methane,
dichloro-, HCC-30
Combine
harvesting
Hard coal, burned
in p
MG-silicon, at
plant
Bipyridyliumcompounds, at
Carbon
monoxide, fossil
Disposal,
antifreezer l
Carbon dioxide,
fossil
Dinitrogen
monoxide
Carbon
monoxide, fossil
Trimethyl borate,
at p
Harvesting, by
comp
Paper, woodfree,
coated
Carbon dioxide,
fossil
Ethylene vinyl
acetate
Carbon dioxide,
fossil
Dinitrogen
monoxide
Agricultural
machinery
Hard coal, burned
i
x
Methane, fossil
Natural gas, at
x
Dinitrogen
monoxide
Operation, coal fre
0.30
x
0.29
x
0.29
x
0.29
x
0.29
x
0.29
x
0.28
x
0.28
Excavation, skidsteer loader
Crude oil,
production NG, at
long
Crude oil,
production RAF,
at lon
Refinery gas,
burned in flare
Operation,
passenger car
Electricity,
hydropower, at
reser
Crude oil,
production RME,
at lon
Refinery gas,
burned in furnace
Treatment,
rainwater mineral
oil
Refinery gas, at
refinery
Urea, as N, at
regional
x
0.28
x
0.28
x
0.28
x
0.28
x
0.28
x
0.27
x
0.27
x
0.27
x
0.27
1-pentanol, at
plant
0.26
0.26
0.27
0.27
Heavy fuel oil, burned in refinery
furnace
Disposal, refinery sludge, 89.5%
water, to sanitary landfill
Methane, biogenic
0.31
0.31
Naphtha, at refinery
0.26
0.26
0.31
Natural gas, burned in boiler
condensing modulating >100kW
0.30
Electricity, low voltage, at grid
0.25
0.25
0.25
0.30
Heat, at cogen with biogas engine,
allocation exergy
Heavy fuel oil, burned in refinery
furnace
Diesel, at refinery
0.25
0.30
0.30
0.30
Excavation, skid-steer loader
0.25
0.30
0.24
Crude oil, production NG, at long
distance transport
0.29
0.24
Crude oil, production RAF, at long
distance transport
0.29
Refinery gas, burned in flare
0.24
0.29
Operation, passenger car
0.24
0.29
0.23
Electricity, hydropower, at reservoir
power plant, alpine region
0.29
0.23
Crude oil, production RME, at long
distance transport
0.28
Refinery gas, burned in furnace
0.23
0.23
0.28
Treatment, rainwater mineral oil
storage, to wastewater treatment,
class 2
Refinery gas, at refinery
0.23
0.28
0.27
Urea, as N, at regional storehouse
0.23
0.27
9
0.08
Methane,
chlorodifluoro-, HCFC22
Ethane, 1,1-dichloro-1fluoro-, HCFC-141b
Ethane, 1,1,2-trichloro1,2,2-trifluoro-, CFC113
0.07
0.01
0.01
storehous
Diesel, at refinery
x
0.25
Carbon dioxide,
fossil
Heavy fuel oil,
burned
Diesel, at refinery
0.23
0.26
42
43
Table S4: CTV results for water scarcity footprint of the “biogas vs. natural gas” comparison. For CTV_all only results >0.1% are included.
CTV_all
Flow
Process
CTV_B
CTV
[%]
Husked nuts harvesting, at farm
Stage
Flow
process
x
Blue water
consumption in
CH
Blue water
consumption in
MY
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
CN
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
FR
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
Rape seed
extensive, at
farm
Palm fruit
bunches, at farm
26.7
Palm fruit bunches, at farm
x
25.8
Rape seed IP, at farm
x
9.3
Protein peas, IP, at farm
x
9.0
Soy beans IP, at farm
x
9.0
Potatoes IP, at farm
x
6.6
Potato seed IP, at farm
x
6.5
Sugarcane, at farm
x
3.0
Blue water
Rape seed
consumption in
extensive, at farm
CH
Maize seed organic, at farm
B
0.5
x
0.3
Blue water
consumption in
MY
Blue water
consumption in
Palm fruit
bunches, at farm
0.2
B
Grass seed IP, at
farm
0.2
B
CTV_x
CTV
[%]
Process
CTV_y
CTV
[%]
19.9
Husked nuts
harvesting, at farm
27.5
9.2
Palm fruit bunches, at
farm
26.6
Grass seed IP, at
farm
7.1
Rape seed IP, at farm
Barley grains
organic, at fa
6.8
Sweet sorghum
stem, at farm
6.4
Maize seed
organic, at farm
6.1
Wheat grains
extensive, at f
5.6
Rape seed IP, at
farm
4.4
Fava beans
organic, at farm
4.3
Maize seed organic, at
farm
0.4
Maize seed IP, at
farm
4.1
Rape seed, organic, at
farm
0.2
Protein peas, IP,
at farm
3.6
Grain maize organic, at
farm
0.2
Potatoes IP, at
farm
3.5
Protein peas, organic,
at farm
0.1
9.6
Protein peas, IP, at
farm
9.3
Soy beans IP, at farm
9.2
Potatoes IP, at farm
6.8
Potato seed IP, at farm
6.7
Sugarcane, at farm
10
3.1
Flow
Blue water
consumption in
PH
Blue water
consumption in
CH
Blue water
consumption in
MY
Blue water
consumption in
BR
Blue water
consumption in
US
Blue water
consumption in
CN
Blue water
consumption in
FR
CTV_C
CTV [%]
47.4
26.4
23.3
2.6
0.2
0.1
0.0
Flow
Blue water
consumption in
FR
Blue water
consumption in
PH
Blue water
consumption in
CH
Blue water
consumption in
MY
Blue water
consumption in
US
Blue water
consumption in
CN
Blue water
consumption in
BR
CTV
[%]
52.8
20.4
12.1
7.3
5.1
2.1
0.1
CH
CH
Blue water
Barley grains
consumption in
organic, at farm
CH
Rape seed, organic, at farm
B
0.2
x
0.2
Blue water
Sweet sorghum
consumption in
stem, at farm
CN
Blue water consumption in FR
B
0.2
C
0.2
Blue water
Maize seed
consumption in
organic, at farm
CH
Grain maize organic, at farm
B
0.2
x
0.1
Blue water
Wheat grains
consumption in
extensive, at farm
CH
Protein peas, organic, at farm
B
0.1
x
0.1
Blue water
Rape seed IP, at
consumption in
farm
CH
Blue water
Fava beans
consumption in
organic, at farm
FR
Grass seed IP, at farm
B
0.1
B
0.1
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
BR
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
US
Blue water
consumption in
PH
Blue water
consumption in
CH
Blue water
consumption in
CH
Blue water
consumption in
CH
Grain maize IP,
at farm
3.5
Grass seed IP, at farm
Potato seed IP,
at farm
3.0
Sugarcane, at
farm
3.0
Rape seed extensive, at
farm
0.1
Protein peas,
organic, at fa
2.8
Sweet sorghum stem,
at farm
0.1
Soy beans IP, at
farm
2.4
0.1
Corn, at farm
0.1
Grain maize IP, at farm
Corn, at farm
0.0
1.7
Fava beans organic, at
farm
0.0
Husked nuts
harvesting, at f
1.5
Wheat grains IP, at
farm
0.0
Grain maize
organic, at farm
0.6
Rape seed,
organic, at farm
0.3
Wheat grains
extensive, at farm
0.0
Wheat grains IP,
at farm
0.1
Barley grains organic,
at farm
0.0
Maize seed IP, at farm
0.0
x
0.1
Corn, at farm
x
0.1
Blue water
consumption in
CH
Maize seed IP, at
farm
B
0.1
44
45
References
46
Aveny GmbH (2011). Aveny LCA tool (NFP66). Zurich
47
Slob W (1994) Uncertainty Analysis in Multiplicative Models. Risk Anal 14(4): 571–576. doi: 10.1111/j.1539-6924.1994.tb00271.x
11