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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

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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