Skog som biobrennstoff: Påvirkning på karbonkretsløp og albedo-effekt

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1 Skog som biobrennstoff: Påvirkning på karbonkretsløp og albedo-effekt Terje Berntsen Universitetet i Oslo og CICERO Med innspill fra Anders Strømman og Ryan Bright, NTNU

2 There is more to do beyond GHG Source: IPCC Biogeophysical interactions also play a prominent role in our climate system and should not be forgotten (See Bonan, Science 2008) 2

3 CO 2 From Biomass Atmosphere A Y CO2 in B Above ground carbon stock X CO 2 out Rotation period, r Time, years Cherubini et al., 2011a 3

4 CO 2 in the Atmosphere during Regrowth Atmosphere A Y CO2 in B Above ground carbon stock Warming during Regrowth X CO 2 out Rotation period, r Time, years Cherubini et al., 2011a 4

5 Both biogenic and anthropogenic CO 2 emissions cause a perturbation to atmospheric CO 2 concentrations This perturbation is modeled with an Impulse Response Function (IRF) to simulate interactions among the atmosphere, the oceans, and the terrestrial biosphere An IRF essentially gives us the time profile of CO 2 in the atmosphere The IRF in IPCC 4AR is for anthropogenic CO 2 and is based on the Bern2.5 carbon cycle-climate model The Bern2.5 IRF does NOT contain formulations to represent constant stock forests in rotation In other words, using it does not allow us to assess radiative forcing impacts of bioenergy sourced from biomass managed in rotation cycles Cherubini et al., 2011a 5

6 Atmospheric Fraction Estimating New IRFs for Biogenic CO Anthropogenic CO2 Time (Year) Cherubini et al., 2011a 6

7 Atmospheric Fraction Estimating New IRFs for Biogenic CO Anthropogenic CO2 Annual crops (r=1 year) Time (Year) Cherubini et al., 2011a 7

8 Atmospheric Fraction Estimating New IRFs for Biogenic CO Anthropogenic CO2 Annual crops (r=1 year) Poplar (r=20 years) Time (Year) Cherubini et al., 2011a 8

9 Atmospheric Fraction Estimating New IRFs for Biogenic CO Anthropogenic CO2 Annual crops (r=1 year) Poplar (r=20 years) Birch (r=60 years) Time (Year) Cherubini et al., 2011a 9

10 Atmospheric Fraction Estimating New IRFs for Biogenic CO Anthropogenic CO2 Annual crops (r=1 year) Poplar (r=20 years) Birch (r=60 years) Spruce (r=100 years) Time (Year) Cherubini et al., 2011a 10

11 11 CO2 ekvivalenter for biobrensel GWP bio AGWP AGWP bioco CO 2 2 C C 0 0 TH 0 TH 0 CO CO 2 2 f t dt y t dt Biogenic CO 2 emissions are treated as the other GHGs Rotation FIRF Annual crops Fast growing biomass Tropical forest Temperate forest Boreal forest r GWP bio GWP bio GWP bio (years) TH = 20 TH = 100 TH =

12 Overarching Research Question Overarching research question: How important is albedo for the assessment of climate impacts of Norwegian ( Boreal) forest biofuels. 12

13 Determine Albedo Coefficients for mature forests and clear cut areas α = 0.13 Actual sky surface albedo data is provided by NASA s moderate-resolution imaging spectroradiometer, or MODIS (MCD43A1 BRDF/Albedo Product, Collection 5) High quality w/snow cover, cloud-cleared results. Data are retrieved for a 9-yr time series spanning January 2001 to December 2009 for each site. 13

14 Albedo and forest regrowth Albedo for clear cut area and full grown forest established earlier. No data on albedo vs age class for Norway Based on literature on Summer Albedo, Canopy Closure etc... Functional form: Linear Average Albedo saturation age: ~ 1/3 of harvest age for Needleleaf ~ 2/5 of harvest age for Birch 14

15 Scenario Analysis Scenario: Increase of logging to 15 Mm 3 /yr from 8.3Mm 3 /yr for the production of bioenergy in Norway for the next 100 years. Case A) Wood based Bio-electricity vs lignite based electricity: Identical efficiency assumptions. GHG: CO2, N2O, CH4 Case B) Wood based Fischer-Tropsch Diesel, conversion efficiency = 45%, No utilization of excess heat. Substitutes fossil diesel, at vehicle. GHG: CO2, N2O, CH4 Landscape-level forest simulation model using data from Norway s 7th National Forest Inventory Carbon accounting is done following IPCC s Gain-Loss (atmospheric flux) method 6 Carbon pools: Above ground living, Below ground living, Litter, Dead wood, Soil organic, Harvested wood products (including biofuels) Yasso07 soil carbon model parameterized for Norwegian conditions is implemented to account for fluxes in soil organic C-pools 15

16 A) Radiative Forcing (RF) Bio vs Coal Increased harvest for bio energy that substitutes lignite results in net cooling over the whole period. 16

17 B) Radiative Forcing (RF) - FTD Albedo Increased harvest for FTD that substitutes gasoline results initial cooling then warming. Better utilization of the energy in the wood feedstock required. E.g Bio-refineries ( fuel, heat, el, chemicals ) 17

18 Konklusjon Er det forskjell på CO 2 fra olje og ved? Nei, CO2 er CO2, men den marginale konsentrasjonsresponsen er forskjelling: Dette gir ulik levetid og ulik klimapåvirkning. Hvordan beregne CO 2 ekvivalenter for biobrensel Beregne absorbert energi fra CO2 gjennom gjennvektsperioden. Hva betyr albedo for klimaeffektene av bioenergi fra norsk skog? For boreal skog så er denne vesentlig Netto kjøling over de neste 100 år for bio vs kull. Energieffektiviteten i utnyttelsen av biobrennstoffet er viktig for nettoeffekten Andre forhold som endringer i evapotranspirasjon, utslipp av andre klimagasser/partikler enn CO2 og muligheten for å forkorte rotasjonsperioden er ikke inkludert her. 18