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Carbon sinks and biofuels:
Optimal greenhouse mitigation
strategies with inclusion of feedback
effects of the global carbon cycle.
Miko U.F. Kirschbaum
CSIRO Forestry and Forest Products &
CRC for Greenhouse Accounting
Canberra, Australia
[email protected]
Pre-industrially
280 ppm
Atmosphere
280 ppm
Oceans
Pre-industrially
Currently
280 ppm
370 ppm
280 ppm
280 ppm
Various fractions of CO2 in the atmosphere enter
into pools with different turn-over times (shallow
ocean, deep ocean, etc.).
About 18% remain permanently in the atmosphere.
Stop
emissions
Atmospheric
CO2 (ppmv)
400
375
350
325
300
1800
1900
2000
2100
2200
Based on “Bern” model as given in IPCC (2000).
2020
2040
2060
2080
2100
0.0
-0.5
-1.0
0.5
0.0
Temperature
difference (10-12 K)
-0.5
-1.0
0
-1
-2
2000
2020
2040
2060
2080
2100
Difference in atmospheric
carbon content (tC)
Extra sink
(tC)
2000
2020
2040
2060
2080
2100
0.0
-0.5
-1.0
0.5
0.0
Temperature
difference (10-12 K)
-0.5
-1.0
0
-1
-2
2000
2020
2040
2060
2080
2100
Difference in atmospheric
carbon content (tC)
Extra sink
(tC)
2000
Which aspect of climate change
impacts us most?
Instantaneous climatic conditions?
• Heat damage
• Severe weather
• Tropical diseases (e.g. malaria)
• Food production
Rate of climate change?
• Ecological mal-adaptation
• Socio-economic institutions
Cumulative climate change?
• Sea level rise
T change (K)
2.5
2000
2020
2040
2060
2080
2100
SRES A2
2.0
1.5
T
1.0
0.5
10

8
6
4
2
0
Cumulative T
(K yr)
150
100

50
0
2000
2020
2040
2060
2080
2100
Rate of T change
[(10-3 K yr-1]
12
0.0
Time ‘bought’ by sinks
2000 2020 2040
80
Permanent
60
2060
2080
2100

Days per GtC
40
T
20

0
Temporary (20 yrs)
10
0
-10
2000
2020
2040
2060
2080
Year of sink activity
2100
Time ‘bought’ by planted forests
2000
10
2020
2040
Days per Mha planted
8
4
0
0.6
2080
2100
2080
2100

6
2
2060
T

0.4
0.2
0.0
-0.2
2000
2020
2040
2060
Planting year
Biofuels
Days per Mha
Instantaneous
impacts only
Substitution
100% efficiency
5
4
3
2
1
50%
0%
0
2000
2020
2040
2060
2080
Initial planting year
2100
20-yr rotations;
replanted after
each harvest
Days per Mha
Biofuels and permanent sinks
5
4
100%
Perm
3
2
1
50%
0%
0
2000
2020
2040
2060
2080
Initial planting year
2100
0
20
Carbon benefit (tC ha-1)
100
40
60
80
100
50% substitution
efficiency
fossil fuel
offset
75
stored C
50
25
0
150
perpetual
sink
100
total biofuel
benefit
50
0
0
20
40
60
Years of growth
80
100
2000
2020
2040
2060
2080
2100
5
100%
4
Perm.
Days per Mha
3
2
1
50%
0%
0
1.5
With wood
products
20-yr
10-yr
1.0
5-yr
0.5
0.0
2000
no storage
2020
2040
2060
2080
Initial planting year
2100
Wood products
with different
product
turn-over times
Relative impact
mitigation
“Business-as-usual” scenario
1.0
SRES A2
0.5

0.0

-0.5
-1.0
0
20
40
60
80
100
Duration of sinks from 2000 (yrs)
Relative impact
mitigation
“Business-as-usual” scenario
1.0
SRES A2
0.5

Average
0.0

-0.5
-1.0
0
20
40
60
80
100
Duration of sinks from 2000 (yrs)
Relative impact
mitigation
“Sustainable” scenario
1.0
SRES B1
0.5


0.0

-0.5
-1.0
0
20
40
60
80
100
Duration of sinks from 2000 (yrs)
Carbon stocks (tC ha-1)
Average Carbon Stock accounting
250
Total
C stocks
200
ACS
150
100
A-g biomass
C stocks
50
0
0
10
20
30
40
Years
50
60
70
Carbon stocks (tC ha-1)
Average Carbon Stock accounting
250
Delayed
200 crediting
150
Credit
100
50
0
0
10
20
30
40
Years
50
60
70
Conclusions (1)
• Permanent carbon storage in
vegetation sinks can make a small,
but useful contribution.
• Temporary storage is much less
valuable than permanent storage, or
not valuable at all.
Conclusions (2)
• The best timing of tree planting
depends on the nature of climate
change impacts:
Plant now if cumulative impacts are
main concern;
Otherwise, later planting may be better
(but that also depends on growth rate).
Conclusions (3)
• Biofuels can make on-going
contribution (similar to permanent).
• Climate-mitigation policy needs to
ensure permanent storage (not
tonne-year accounting).
References:
1.
Kirschbaum, M.U.F., Schlamadinger, B., Cannell, M.G.R.,
Hamburg, S.P., Karjalainen, T., Kurz, W.A., Prisley, S., Schulze,
E.-D., and Singh, T.P. (2001): A generalised approach of accounting
for biospheric carbon stock changes under the Kyoto Protocol.
Environmental Science and Policy 4: 73-85.
2.
Kirschbaum, M.U.F. (2003). To sink or burn? A discussion of the
potential contributions of forests to greenhouse gas balances
through storing carbon or providing biofuels. Biomass and
Bioenergy 24: 297-310.
3.
Kirschbaum, M.U.F. (2003). Can trees buy time? An assessment of
the role of vegetation sinks as part of the global carbon cycle.
Climatic Change 58: 47-71.
Thank you!