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LCA of biogas from different purchased
substrates and energy crops
47th LCA Discussion Symposium
Berne, 23. April 2012
Matthias Stucki, Niels Jungbluth
ESU-services Ltd., Uster, Switzerland
USE USE
www.esu-services.ch Page 2
Introduction • Most Biogas in CH from sewage sludge, slurry, or
biowaste.
• In order to improve the yield of biogas plants,
operators often purchase or cultivate substrates
with high energy content.
• Environmental impacts of biogas from these
substrates?
www.esu-services.ch Page 3
Substrates considered in this study
Sugar beet Fodder beet Beet residues
www.esu-services.ch Page 4
Substrates considered in this study
Maize silage Molasses Glycerine
a) From vegetable oil
b) From waste oil
www.esu-services.ch Page 5
Life cycle inventory analysis • New LCI of biogas from different substrates
– Literature data
– Results from survey (ENERS)
• New LCI of methane purification technologies
• Updated LCI of biogas combustion in
cogeneration unit
• Modelling of biogas based car driving with
ecoinvent data
www.esu-services.ch Page 6
Biogas system overview
0
40
80
120
160
200
mai
ze s
ilage
suga
r b
eet
fod
der
bee
t
bee
t re
sid
ues
mo
lass
es
rap
e o
il gl
ycer
ine
was
te o
il gl
ycer
ine
CH
mix
of
pu
rifi
ed b
ioga
s
die
sel
nat
ura
l gas
pet
rol
new inventories biogas co-substrates ecoinvent v2.2 conventional
gCO2-eq./pkm
Car infrastructure Road infrastructure Car operation
Biogas purification Biogas production Fossil fuel production
Page 7
Results: car transportation with biogas Greenhouse gases
threshold for tax reduction of biofuels
0
50
100
150200250
300350
400
mai
ze s
ilage
suga
r b
eet
fod
der
bee
t
bee
t re
sid
ues
mo
lass
es
rap
e o
il gl
ycer
ine
was
te o
il gl
ycer
ine
CH
mix
of
pu
rifi
edb
ioga
s die
sel
nat
ura
l gas
pet
rol
new inventories biogas co-substrates ecoinvent v2.2 conventional
ecopoints/pkmCar infrastructure Road infrastructure Car operation
Biogas purification Biogas production Fossil fuel production
Page 8
Results: car transportation with biogas Ecological Scarcity
threshold for tax reduction of biofuels
Substrate
production &
cultivation
Biogas
production
Digestate
application on
land
Agricultural
plant
cultivation
Wastewater treatment
(production of sewage sludge)
Biogas production
Disposal of digested
sewage sludge
Substrate
collection and
transport
Animal
breeding
(manure
production)
Biogas
production
Manure
application on
land
Agricultural
plant
cultivation
Transport
Allocated to wastewater
treatment
Allocated to biogas production
Allocated to animal
breeding
Allocated to biogas
production Allocated to plant cultivation
Allocated to biogas production
Emissions
from
manure
storage
Additional
emissions
from storage
Additional
emissions
from
digestate
application
Allocated to plant cultivation
SUBSTRATE BIOGAS DIGESTATE
Biogas from
sewage
sludge in
ecoinvent
v2.2
Biogas from
manure in
ecoinvent
v2.2
Biogas from
high energy
substrates in
this study
Allocation
Substrate
production &
cultivation
Biogas
production
Digestate
application on
land
Agricultural
plant
cultivation
Substrate
collection and
transport
Allocated to biogas production Allocated to
plant cultivation
SUBSTRATE BIOGAS DIGESTATE
Allocation: scenario
Substrate
production &
cultivation
Biogas
production
Digestate
application on
land
Agricultural
plant
cultivation
Substrate
collection and
transport
Allocated to biogas production Allocated to plant cultivation
www.esu-services.ch Page 10
Standard
case:
Scenario:
0
50
100
150
200
250
300
350
400
mai
ze s
ilage
suga
r b
eet
fod
der
bee
t
bee
t re
sid
ues
mo
lass
es
rap
e o
il gl
ycer
ine
was
te o
il gl
ycer
ine
CH
mix
of
pu
rifi
edb
ioga
s die
sel
nat
ura
l gas
pet
rol
new inventories biogas co-substrates ecoinvent v2.2 conventional
ecopoints/pkmCar infrastructure Road infrastructure Car operation Biogas purificationBiogas production Fossil fuel production Digestate application
Page 11
Scenario: Including application of digestates Ecological Scarcity
threshold for tax reduction of biofuels
-
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60 70 80 90 100 110
t CO2-eq./ha
1'000 km/ha
rape methyl ester
ethanol from sugar beets
ethanol from corn (from USA)
miscanthus BTL
wood BTL-CUTEC
wood BTL-TUV
wood BTL-UET
soy methyl ester (from Brazil)
soy methyl ester (from USA)
palm oil methyl ester
biogas from sugar beets
biogas from fodder beet
biogas from grass
biogas from maize silage
biogas from rape glycerine
www.esu-services.ch Page 12
Results: yield and impact per hectare Greenhouse gases
-
5
10
15
20
25
30
35
40
45
50
0 10 20 30 40 50 60 70 80 90 100 110
Mio ecopoints/ha
1'000 km/ha
rape methyl ester
ethanol from sugar beets
ethanol from corn (from USA)
miscanthus BTL
wood BTL-CUTEC
wood BTL-TUV
wood BTL-UET
soy methyl ester (from Brazil)
soy methyl ester (from USA)
palm oil methyl ester
biogas from sugar beets
biogas from fodder beet
biogas from grass
biogas from maize silage
biogas from rape glycerine
www.esu-services.ch Page 13
Results: yield and impact per hectare Ecological Scarcity
www.esu-services.ch Page 14
• Yield and environmental impacts of producing biogas
from cultivated energy crops are in the same range as
compared to liquid biofuels.
• The case of sugar beets indicates that the bioethanol
route is more efficient than the biogas conversion route
for producing biofuels.
Results: yield and impact per hectare
-250
0
250
500
750
1000
1250
mai
ze s
ilage
suga
r b
eet
fod
der
bee
t
bee
t re
sid
ues
mo
lass
es
rap
e o
il gl
ycer
ine
was
te o
il gl
ycer
ine
bio
was
te &
sew
age
slu
dge
slu
rry
CH
gri
d m
ixnew inventories ecoinvent v2.2
ecopoints/kWh electricity
Water recourses
Toxic hydrocarbons
Ozone depletion
Mineral resources
NMVOC
Heavy metals to air
Radioactive waste
Land resources
Energy resources
Pesticides
Radioactive water
Eutrophication
Human health
Acidification
Climate changewww.esu-services.ch Page 15
Results: electricity generation from biogas Ecological Scarcity
www.esu-services.ch Page 16
Conclusions 1
• Some environmental benefits of using biogas from
purchased substrates compared to fossil fuels
• Higher environmental impacts of biogas from purchased
substrates compared to waste substrates
• Allocation of digestate application has a high impact on
results
www.esu-services.ch Page 17
Conclusions 2
• Pure biogas production from purchased substrates does
mostly not comply with thresholds for tax reductions
• In contrast to electricity from biogas produced with
wastes, electricity from biogas produced with cultivated
crops is not favourable from an environmental view:
emissions from crop cultivation and biogas combustion
www.esu-services.ch Page 18
Conclusions
The current trend towards using high energy substrates
made from agricultural crops leads to higher
environmental impacts and a worse environmental
performance of biogas.
Page 19
Thank you very much for your attention!
Matthias Stucki
www.esu-services.ch
ESU-services, Uster, Schweiz
Acknowledgements: The work presented here was made possible thanks to
financial support from the Swiss Federal Office for Energy (FOEN).
Download the study and electronic data: http://www.lc-inventories.ch/
www.esu-services.ch Page 20
Additional Slides
www.esu-services.ch Page 21
Results: car transportation with biogas Eco-Indicator 99 (H, A)
0.0E+00
5.0E-03
1.0E-02
1.5E-02
2.0E-02
2.5E-02
3.0E-02
mai
ze s
ilage
suga
r b
eet
fod
der
be
et
bee
t re
sid
ue
s
mo
lass
es
rap
e o
il gl
yce
rin
e
gras
s re
fin
ery
(gra
ss &
co
w s
lurr
y)
gras
s re
fin
ery*
(gr
ass
& c
ow
slu
rry)
was
te o
il gl
ycer
ine
Swis
s m
ix o
f p
uri
fie
d b
ioga
s (t
his
stu
dy)
bio
was
te
fat
and
oil
sew
age
slu
dge
slu
rry
wh
ey
die
sel
nat
ura
l gas
pet
rol
new inventories biogas co-substrates ecoinvent v2.2 biogas ecoinvent v2.2conventional
EIP 99/pkm Fossil fuels Minerals Land use Acidification/ Eutrophication
Ecotoxicity Ozone layer Radiation Climate change
Resp. inorganics Resp. organics Carcinogens
threshold for tax reduction of biofuels
www.esu-services.ch Page 22
Allocation of biowaste digestion in
ecoinvent v2.2 Agricultural digestion
plant (Biowaste)
Substrate treatment Biogas production Digestate application
Biogas plant 100% -
Energy consumption 55% 45% -
NH3 & N2O emissions 47% 39% 14%
CH4 & HS emissions 55% 45% -
Emissions into soil 50% - 50%
Anaerobic digestion
plant (Biowaste)
Substrate treatment Biogas production Digestate application
Biogas plant 69% 31% -
Energy consumption 69% 31% -
Ammonia emissions 64% 22% 14%
CH4 & HS emissions 69% 31% -
Emissions into soil 50% - 50%
www.esu-services.ch Page 23
Biogas purification
3 Technologies in CH
• pressure swing
adsorption (PSA)
• glycol washing
• amino washing
Glycol washing in Pratteln
