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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
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The traditional starting point
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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
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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
6
The forest’s standard parcel
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Speed of decomposition of deadwood
100
Harvest residues
Natural dead wood
Percentage
75
50
25
0
0
25
50
75
100
Years after natural death or felling
8
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Increase of the the forest's carbon stock
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Mill. tonnes carbon
300
250
200
150
100
50
0
2000
2100
2200
Reference scenario (no harvest)
Harvest scenario (8.2 Mm3/yr incl residues)
2300
Consider an
area of 34 000
km2
Two scenarios:
No harvest
Annual harvest
of 6.8 Mm3/year
+ 1.4 Mm3
residues/year
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.
250
Million tonnes carbon
200
150
100
50
0
2000 2050 2100 2150 2200 2250 2300 2350 2400
Drop in the forest's carbon stock due to increased
logging
Accumulated reduction in carbon emissions from fossil
oil combustion
Accumulated reduction in carbon emissions from coal
combustion
10
250
Million tonnes carbon
200
150
100
50
0
-50
2000 2050 2100 2150 2200 2250 2300 2350 2400
Drop in the forest's carbon stock due to increased
logging
Accumulated reduction in carbon emissions from fossil
oil combustion
Accumulated reduction in carbon emissions from coal
combustion
Remaining carbon debt - biodiesel
Remaining carbon debt - pellets
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250
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150
100
Next step:
Total effect on
radiative forcing,
taking albedo into
account
CO2 Impulse response function (IRF)
50
1
Share remaining in the atmosphere
Million tonnes carbon
200
0
-50
2000 2050 2100 2150 2200 2250 2300 2350 2400
0.75
0.5
Drop in the forest's carbon stock due to increased
logging
Accumulated reduction in carbon emissions from fossil 0.25
oil combustion
Accumulated reduction in carbon emissions from coal
combustion
0
Remaining carbon debt - biodiesel
0
Remaining carbon debt - pellets
100
200
300
400
Time since emission
12
5
800
4
600
3
400
2
CO2 concentration in high emission scenario
CO2 concentration in low emission scenario
200
1
Temperature increase in high emission scenario
Temperature increase in low emission scenario
0
2000
0
2050
2100
2150
Time
2200
2250
2300
Temperature increase (°C)
CO2 concentration (ppmv)
1 000
250
200
5
150
100
2.5
Million tonnes
Million
tonnescarbon
carbon
Radiative forcing 10-4 W/m2
7.5
50
0
2000
2050
2100
2150
2200
2250
0
2300
Year
High emission scenario
RF due to the carbon flux - harvest
Low emission scenario
RF
due
to the
carbon
flux - harvest
Drop
in the
forest's
carbon
stock due to
increased logging
Drop in the forest's carbon stock due to
increased logging
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Scenario with constant CO2 concentration
Radiative forcing 10-4 W/m2
7.5
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
Year
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
2300
Low emissions scenario
Radiative forcing 10-4 W/m2
7.5
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
Year
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
2300
High emissions scenario
Radiative forcing 10-4 W/m2
7.5
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
2300
First conclusion:
RF due to the carbon flux - harvest
Harvesting of wood
RF change due to albedo
fuels is not a climate
RF - net total change due to harvest/combustion of wood fuels
neutral activity – even
if albedo is accounted
for
Year
Next question:
Is wood fuels better or worse than fossil
fuels?
Scenario with constant CO2 concentration
Radiative forcing 10-4 W/m2
7.5
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
Year
RF due to the carbon flux - harvest
RF change due to albedo
RF - net total change due to harvest/combustion of wood fuels
2300
Scenario with constant CO2 concentration
Radiative forcing 10-4 W/m2
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
Year
RF due to the carbon flux - biodiesel
RF - net total change - biodiesel
RF - net total change due to harvest/combustion of wood fuels
2300
Low emission scenario
Radiative forcing 10-4 W/m2
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
Year
RF due to the carbon flux - biodiesel
RF - net total change - biodiesel
RF - net total change due to harvest/combustion of wood fuels
2300
High emission scenario
Radiative forcing 10-4 W/m2
5
2.5
0
-2.5
2000
2050
2100
2150
2200
2250
Year
RF due to the carbon flux - biodiesel
RF - net total change - biodiesel
RF - net total change due to harvest/combustion of wood fuels
2300
Net effect on RF - biodiesel
case
Radiative forcing 10-4 W/m2
3
2
1
0
-1
-2
Second conclusion:
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2000
2050
2100
2150
2200
Year
Constant CO2-level
Low emission scenario
Harvesting of wood fuels
does not appear to be
2250
good
climate2300
policy –
even if albedo is
High emissionfor
scenario
accounted
and the
wood fuels replaces petrol
or diesel
Net effect on RF - pellets/coal case
Radiative forcing 10-4 W/m2
2
1
0
-1
-2
Third conclusion:
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2000
2050
2100
2150
2200
When wood fuels
replaces coal, the climate
2250 are 2300
impacts
less clear
Year
Constant CO2-level
Low emission scenario
High emission scenario
A map of the boreal forests
Background
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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
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