is biomass from boreal forests better or worse than fossil fuels from a climate perspective?
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Is biomass from boreal forests better or worse than fossil fuels from a climate perspective?. A work in progress By Bjart Holtsmark Statistics Norway. The traditional starting point. Sjølie, H. K., E. Trømborg, B. Solberg and T. F. Bolkesjø in Forest Policy and Economics 12, 57-66, (2010) - PowerPoint PPT PresentationTRANSCRIPT
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Is biomass from boreal forests Is biomass from boreal forests better or worse than fossil better or worse than fossil fuels from a climate fuels from a climate perspective? perspective?
A work in progress
By Bjart Holtsmark
Statistics Norway
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The traditional starting point
• Sjølie, H. K., E. Trømborg, B. Solberg and T. F. Bolkesjø in Forest Policy and Economics 12, 57-66, (2010)
• “The objective of this study is [..] to analyse [..] the impacts on GHG emissions by replacing one energy unit of fossil fuel with wood fuel in various types of heating facilities.”
• At the same time they write:• “CO2 is excluded in calculation of emissions from combustion [of wood],
as wood is considered carbon neutral”.• Their conclusion: Increased use of biomass from the Norwegian forest
will provide climate benefits.• Similar arguments and conclusion found in several recent studies, for
example Bright RM, Strømman AH (2009) Life cycle assessment of second generation bioethanol produced from Scandinavian boreal forest resources. J IndEcol 13:514–530
• Bright, Strømman, Peters (2011) • New paper, taking both CC and albedo into account – work in progress!
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The forest’s standard parcel• An overlapping
generations model of trees
• The model consists of a set of parcels, each of 1 km2, all with the same properties, but with different time since last clear cutting (age)
• Productivity follows the Braastad (1975) production tables – probably too small areas - adjusted
• As dead wood decomposes slowly, this gives accumulation of dead wood in older forests – important part of the forests carbon stock
• After clearcutting in a parcel the growth path restarts
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The forest’s standard parcel
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The forest’s standard parcel
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The forest’s standard parcel
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The forest’s standard parcel
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Speed of decomposition of deadwood
0
25
50
75
100
0 25 50 75 100
Years after natural death or felling
Per
cent
age
Harvest residues
Natural dead wood
Increase of the the forest's carbon stock
0
50
100
150
200
250
300
2000 2100 2200 2300
Mill
. ton
nes
carb
on
Reference scenario (no harvest)Harvest scenario (8.2 Mm3/yr incl residues)
• Consider an area of 34 000 km2
• Two scenarios:• No harvest• Annual harvest
of 6.8 Mm3/year + 1.4 Mm3 residues/year
10
0
50
100
150
200
250
2000 2050 2100 2150 2200 2250 2300 2350 2400
Mill
ion
tonn
es c
arbo
n
Drop in the forest's carbon stock due to increasedloggingAccumulated reduction in carbon emissions from fossiloil combustionAccumulated reduction in carbon emissions from coalcombustion
Two examples:
• First case, the wood is used as the raw material for manufacturing pellets. The pellets then replace coal in power plants
• In the second case, wood is used for producing second generation liquid biofuels, and replaces petrol or diesel.
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-50
0
50
100
150
200
250
2000 2050 2100 2150 2200 2250 2300 2350 2400
Mill
ion
tonn
es c
arbo
n
Drop in the forest's carbon stock due to increasedloggingAccumulated reduction in carbon emissions from fossiloil combustionAccumulated reduction in carbon emissions from coalcombustionRemaining carbon debt - biodiesel
Remaining carbon debt - pellets
12
-50
0
50
100
150
200
250
2000 2050 2100 2150 2200 2250 2300 2350 2400
Mill
ion
tonn
es c
arbo
n
Drop in the forest's carbon stock due to increasedloggingAccumulated reduction in carbon emissions from fossiloil combustionAccumulated reduction in carbon emissions from coalcombustionRemaining carbon debt - biodiesel
Remaining carbon debt - pellets
CO2 Impulse response function (IRF)
0
0.25
0.5
0.75
1
0 100 200 300 400
Time since emission
Sh
are
re
ma
inin
g in
the
atm
osp
he
re
• Next step:
• Total effect on radiative forcing, taking albedo into account
0
200
400
600
800
1 000
2000 2050 2100 2150 2200 2250 2300
Time
CO
2 c
on
cen
tra
tion
(p
pm
v)
0
1
2
3
4
5
Te
mp
era
ture
incr
ea
se (
°C)
CO2 concentration in high emission scenario
CO2 concentration in low emission scenario
Temperature increase in high emission scenario
Temperature increase in low emission scenario
14
0
2.5
5
7.5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
0
50
100
150
200
250
Mill
ion
ton
ne
s ca
rbo
n
RF due to the carbon flux - harvest
Drop in the forest's carbon stock due toincreased logging
0
2.5
5
7.5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
0
50
100
150
200
250
Mill
ion
tonn
es c
arbo
n
High emission scenario
Low emission scenario
RF due to the carbon flux - harvest
Drop in the forest's carbon stock due toincreased logging
Scenario with constant CO2 concentration
-2.5
0
2.5
5
7.5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
Low emissions scenario
-2.5
0
2.5
5
7.5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
High emissions scenario
-2.5
0
2.5
5
7.5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
First conclusion: Harvesting of wood fuels is not a climate neutral activity – even if albedo is accounted for
Next question: Is wood fuels better or worse than fossil fuels?
Scenario with constant CO2 concentration
-2.5
0
2.5
5
7.5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
Scenario with constant CO2 concentration
-2.5
0
2.5
5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - biodiesel
RF - net total change - biodiesel
RF - net total change due to harvest/combustion of wood fuels
Low emission scenario
-2.5
0
2.5
5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - biodiesel
RF - net total change - biodiesel
RF - net total change due to harvest/combustion of wood fuels
High emission scenario
-2.5
0
2.5
5
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
RF due to the carbon flux - biodiesel
RF - net total change - biodiesel
RF - net total change due to harvest/combustion of wood fuels
Net effect on RF - biodiesel case
-4
-3
-2
-1
0
1
2
3
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
Constant CO2-level Low emission scenario High emission scenario
Second conclusion:
• Harvesting of wood fuels does not appear to be good climate policy – even if albedo is accounted for and the wood fuels replaces petrol or diesel
Net effect on RF - pellets/coal case
-4
-3
-2
-1
0
1
2
2000 2050 2100 2150 2200 2250 2300
Year
Ra
dia
tive
forc
ing
10
-4 W
/m2
Constant CO2-level Low emission scenario High emission scenario
Third conclusion:
• When wood fuels replaces coal, the climate impacts are less clear
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Background• Based on the assumption of
climate neutrality, wood fuels from the Scandinavian forest have conventionally, from a climate perspective, been considered as a better energy source than fossil fuels.
• Policies in order to increase the supply of biofuels through increased harvest from the forest.
• In this paper I find: • Wood fuels are not climate
neutral and that continued use of fossil fuels is in most cases a better alternative than increased use of biomass from the forest.
• Relevance beyond the Scandinavian debate:
• The Scandinavian forest is part of the vast boreal forests
A map of the boreal forests