Prospective Environmental Assessments BIOGENIC CARBON ACCOUNTING

Transcription

1 Prospective Environmental Assessments BIOGENIC CARBON ACCOUNTING Bernhard Steubing April 29th, 2015

2 Global carbon cycle Major carbon pools and fluxes of the global carbon balance in Giga tons of carbon (GtC) [10]. Petrokofsky et al. Environmental Evidence :6 doi: /

3 Metrics for measuring climate change IPCC 2013, chapter 8 GWP GTP* Human health Ecosystem effects * Global temperature potential 3

4 Impulse response function (IRF) of CO2 according to different models Modelled responses to a pulse emission at time 0 Despite terrestrial and oceanic uptake, some CO 2 remains for a very long time in the atmosphere (new equilibrium) It is a complex system uncertainty in the predictions Especially for the cumulative effect Joos et al

5 Global warming potential (GWP) ( relative cumulative forcing index (IPCC 2013)) Index of total energy added to the atmosphere over a given time horizon Based on radiative forcing of greenhouse gases (GHG) in the atmosphere GWP measures the effect of GHGs relative to the effect of CO 2 GHG X GHG Y radiative efficiency decay Substance Lifetime (y) GWP 20y GWP 100y Carbon dioxide (CO 2 ) 1 1 Methane (CH 4 ) Nitrous oxide (N 2 O) CO 2 Tetrafluoromethane (CF 4 ) y time 100 y

6 Carbon cycle of biomass systems Aren t forests (at least sustainably managed ones) carbon neutral? Doesn t carbon neutrality mean climate neutrality? Which factors could influence carbon or climate neutrality so that accounting for biogenic carbon emissions (and uptake) becomes necessary? CO2 fossil = CO2 biogenic (in terms of atmospheric effect) Image source:

7 Outline biogenic carbon emissions accounting Why? Carbon stock changes Timing of emissions Reference scenario How? The GWP bio indicator Current assessment methods LCA Standards (ISO TR 14067, PAS 2050, GHG protocol) National GHG accounting Summary and conclusions Exercise Non-carbon climate effects from biomass 7

8 WHY TO ACCOUNT FOR BIOGENIC CARBON EMISSIONS? 8

9 C-forest Forest-atmosphere C dynamics in a managed forest Forest-C time Atmospheric-C = = = = = What influences biomass climate neutrality?

10 1. Carbon stock changes Forest Atmosphere This situation is neither carbon nor climate neutral in LCA often biogenic carbon is assumed to be carbon neutral by default. This means that even if biogenic carbon emissions are modelled, they might not be counted (i.e. CF of biogenic carbon in LCIA methods could be zero)

11 Deforestation 2000 Source: FAO 2012, State of the World s Forests Source: NASA

12 Carbon stock change through land use changes??

13 ILUC indirect land use changes Figure from: Indirect land use and biofuels, 2011, European Parliament 13

14 Carbon stock change & forest management e.g. change to short rotation forest Stock reduction 100 years 30 years

15 2. Timing of emissions and sequestration Forest-C Atmospheric-C Carbon neutrality does NOT necessarily imply climate neutrality = = = = Natural state Use by humans The timing of emissions and sinks has an impact on the overall cumulative climatic impact (Levasseur 2010, 2012; Cherubini et al. 2011)

16 Factors affecting the timing Speed of biomass re-growth Storage of biomass products (e.g. furniture) Decay of harvest residues (branches, leafs) Harvest method (clear-cutting vs. selective harvesting: speed of re-growth and forest-soil interaction)

17 Starting situation dilemma (chicken or egg) : chicken Initial C-stock 1800: egg Initial C-stock Mommy, how cool, by growing forests we can mitigate climate change!! Impacts Benefits No darling, every rotation period we contribute to climate change!! (eggs the sweetest things, but sooo naïve ) The chicken s perspective seems to be more accepted (Helin 2013)

18 3. Reference scenario Is extraction of wood from forests a loss of sequestration potential? X Unused additional GWP benefits through sequestration So far no guidance in directives, standards and guidelines on how to define a reference scenario (Helin 2013). Different approaches are used.

19 Results of different accounting procedures ( Baseline problem; Johnson 2012) C-footprint of bioenergy from wood cut on purpose for biofuels Four different baselines: No baseline, but carbon neutrality Reference point: net carbon stock compared between start-end of reference period (used in Kyoto protocol) Marginal fossil fuel: net C emissions from forest minus emissions from a fossil-fuel-fired alternative (consistent with CLCA) Biomass opportunity cost: carbon debt, as forest would have stored more (consistent with CLCA) Baseline (i.e. calculation procedures) is the greatest single influence on the footprint

20 Summary Why to account for C-bio (mechanisms)? Carbon stock changes Timing of emissions and uptake Baseline / reference scenario physical reality counterfactual (what would have been)

21 BIOGENIC CARBON EMISSIONS ACCOUNTING: METHOD OF CHERUBINI AND COLLEAGUES 21

22 Cherubini method (2011): Convolution between atmospheric CO 2 decay and carbon sequestration in biomass atmospheric CO 2 decay growth function atmospheric CO 2 decay (convolution) t f t = y t g t y t t dt 0 FIRF = full impulse response function (based on Bern 2.5 CC model) - Terrestrial uptake - Oceanic uptake g(t ) y(t) 22

23 GWP bio indicator (FIRF) Describes the climate change effect of biogenic carbon relative to the same emission of fossil carbon 0 = no climate effect 1 = climate effect like fossil CO 2 Strong influence of time horizon Rotation period TH=20 TH=100 TH=

24 Influence of time horizon (TH) Chosen time horizon (TH) has a strong influence (no objective / scientific basis for TH choice it remains a value choice) 24

25 Possible climate change impact of biogenic CO 2 Steubing, B., Die Ökobilanz der energetischen Holzverwertung: Faktoren für einen hohen ökologischen Nutzen. Schweizerische Zeitschrift für Forstwesen Method of Cherubini et al TH = 100 years 25

26 Extensions to the GWP bio indicator Decay of forest harvest residues (Guest et al GCB) Storage (Guest et al JIE) Carbon stock changes (Cherubini et al. 2013, JEM) Reference scenario is not a physical reality and therefore accounted for separately Formula extension (showing only the principle, in reality it is more complicated): 26

27 Temporary storage Temporary storage results in a delay in the timing of emissions The forest continues to sequester CO 2 The longer the storage, the lower the GWP bio Guest et al

28 GWP bio (rotation period & storage) Source: Guest et al

29 Cascade use of wood increases storage time Höglmeier, K., Res. Cons. Recyc

30 BIOGENIC CARBON ACCOUNTING IN CARBON FOOTPRINTING GUIDELINES 30

31 Guidelines related to carbon accounting (selection) International Standard Organisation EPD / ISO (env. labeling) ISO ISO TR (carbon footprint) (2013) IPCC (United Nations) Guidelines for national GHG inventories (2006) European ILCD handbook Product Environmental Footprint (PEF) Guide (2013) Product focus NGO GHG protocol (WRI / WBCSD) (2011) National PAS 2050 (GHG accounting, British) (2008/2011) BP X (good practices, env. labeling, France) 31

32 ISO (carbon footprint) Emissions Biogenic carbon emissions and removals included (assumption of carbon and climate neutrality, if biomass removals and emissions are equal) Non-CO2 emissions (e.g. methane) like fossil ones Timing of emissions: not accounted for Storage Shall be reported separately Is not counted to the environmental footprint of a product (no benefits) 32

33 PAS 2050 Emissions Biogenic carbon emissions are excluded from accounting (assumption of carbon neutrality) unless it arises from land use changes Other biogenic GHG (e.g. methane) are included Storage Carbon storage shall be included where: biogenic carbon forms of a product (e.g. wood fibre in a table) atmospheric carbon is taken up by a product (sequestration) over its life cycle (e.g. cement) 33

34 Summary: product carbon footprint Biogenic carbon ISO PAS 2050 GHG protocol Cherubini et al. Stock changes Yes Yes Yes Yes. All issues within one Emissions and removals Timing of emissions / removals (except storage) Storage Yes, reported separately. No. Unless from land-use change. No No No No. Shall not be counted for CF, but reported separately. Yes (weighted by duration). Full benefit, if carbon is stored > 100 years. Shall be reported separately. Yes, reported separately. No. Unless carbon is stored > TH of study, (min. 100 years, full benefit). Delayed emissions can be reported separately. formula describing the carbon flows to an from the atmosphere, i.e. the carbon exchanges between biomass production, terrestrial and oceanic uptake as well as product use. Reference scenario No No No No. Can be accounted for separately from the above formula (not part of the physical reality ). 34

35 GWP Comparison of approaches to account for temporary storage of biogenic carbon GWP bio approach: Guest et al Other approaches: Impact 0 ISO GHG protocol PAS years

36 Carbon storage in PAS 2050 Source: Rolf Frischknecht PAS 2050 impact (benefit) of biogenic carbon due to storage: -42 t According to physical GWP bio model: -0.16*60 = -9.6 t (with R = 100, TH = 100, storage = 70 years) 36

37 BIOGENIC CARBON ACCOUNTING UNDER THE KYOTO PROTOCOL 37

38 IPCC, UNFCCC, Kyoto Protocol IPCC, 1988: scientific intergovernmental body under the UN, produces reports/guidelines for the UNFCCC, e.g. 5th Assessment Report 2014 ( Guidelines for National GHG inventories Earth Summit, 1992: Negotiation of a treaty called: United Nations Framework Convention on Climate Change (UNFCCC) Aim: stabilize greenhouse gas concentrations to prevent dangerous anthropogenic interference with the climate system Not legally binding, but framework for negotiation of protocols Kyoto Protocol, 1997: Legally binding GHG reduction targets for developing countries Reporting of National GHG inventories Flexibility mechanisms: emission trading, clean development mechanisms (CDM), joint implementation (JI), etc. 38

39 Kyoto Protocol Participation 39

40 Kyoto protocol: C pools in national GHG inventories 2006 IPCC Guidelines for National Greenhouse Gas Inventories 1 st commitment period nd commitment period

41 1 st period of Kyoto protocol Swiss commitment 100% GHG-Emissions 1990 (without sink) -8% Reduction+ Certificate 40% 2.4 Mt CO 2 60% Reduction + Certificate Forest Sink 92% 4.2 Mt CO 2 Forest Sink 1.8 Mt CO Slide from Paolo Camin / BAFU

42 1 st period of Kyoto protocol Gains outweigh losses Forest represents a net carbon sink for Switzerland (due to underused forests) Cap of 1.8 Mt CO2 Based on material from Paolo Camin / BAFU

43 2 nd period of Kyoto protocol Forest and HWP accounting Forest - Pools HWP- Pool HWP Sawnwood Panels Paper Harvest Source Recovered wood Source Soil increment Litter Dead wood Sink HWP production Sink Slide from Paolo Camin / BAFU

44 Summary: national GHG inventory accounting Biogenic carbon Kyoto Protocol Cherubini et al. Stock changes Emissions and removals Timing of emissions / removals (except storage) Storage Yes. Detailed differentiation of carbon pools. Yes. Different sources distinguished. No Yes. HWP, but no benefit for storage given. Net emissions from HWP possible. Yes. All issues within one formula describing the carbon flows to an from the atmosphere, i.e. the carbon exchanges between biomass production, terrestrial and oceanic uptake as well as product use. Reference scenario No No. Can be accounted for separately from the above formula (not part of the physical reality ). IPCC 5 th Assessment Report (Physical Science Basis, Chapt. 8): Mentions the work of Cherubini et al. under New Metric Concepts, but does not (yet) apply it It states that GWP bio and GTP bio have been used in only a few applications, and more research is needed to assess their robustness and applicability. 44

45 Take home messages Biogenic carbon emissions are neither carbon neutral nor climate neutral by default Carbon stock changes, timing of emissions and reference scenario should be considered GWP bio approach of Cherubini et al. accounts for both biomass sequestration and atmospheric decay of biogenic carbon Factors such as carbon stock changes, timing of emissions as well as biomass re-growth curve and storage time of products can be considered chosen time horizon strongly affects the results Biogenic carbon flows can have considerable influence on the climate impact of biomass products and bioenergy Currently, different approaches are used in guidelines and scientific literature (no consensus yet) need for harmonization Generally, guidelines do not yet consider the timing of emissions All methods and their results have inherent uncertainties 45

46 Literature IPCC, 5 th Assessment Report 2014 ( Cherubini, F., G. P. Peters, et al. (2011). "CO 2 emissions from biomass combustion for bioenergy: Atmospheric decay and contribution to global warming." GCB Bioenergy 3(5): Guest, G.; Cherubini, F.; Strømman, A. H., Global Warming Potential of Carbon Dioxide Emissions from Biomass Stored in the Anthroposphere and Used for Bioenergy at End of Life. Journal of Industrial Ecology 2013, 17, (1), Cherubini, F., G. Guest, et al. (2013). "Bioenergy from forestry and changes in atmospheric CO2: Reconciling single stand and landscape level approaches." Journal of Environmental Management 129: Helin, T., L. Sokka, et al. (2013). "Approaches for inclusion of forest carbon cycle in life cycle assessment - A review." GCB Bioenergy 5(5): Brandão, M., A. Levasseur, et al. (2013). "Key issues and options in accounting for carbon sequestration and temporary storage in life cycle assessment and carbon footprinting." International Journal of Life Cycle Assessment 18(1): Further reading: Levasseur, A., M. Brandão, et al. (2012). "Valuing temporary carbon storage." Nature Climate Change 2(1): 6-8. Levasseur, A., P. Lesage, et al. (2010). "Considering time in LCA: Dynamic LCA and its application to global warming impact assessments." Environmental Science and Technology 44(8): Bright, R. M., F. Cherubini, et al. (2012). "Climate impacts of bioenergy: Inclusion of carbon cycle and albedo dynamics in life cycle impact assessment." Environmental Impact Assessment Review 37: Cherubini, F., R. M. Bright, et al. (2012). "Site-specific global warming potentials of biogenic CO2 for bioenergy: Contributions from carbon fluxes and albedo dynamics." Environmental Research Letters 7(4). Cherubini, F., R. M. Bright, et al. (2013). "Global climate impacts of forest bioenergy: What, when and how to measure?" Environmental Research Letters 8(1). Johnson, E. (2009). "Goodbye to carbon neutral: Getting biomass footprints right." Environmental Impact Assessment Review 29(3): Johnson, E. and D. Tschudi (2012). "Baseline effects on carbon footprints of biofuels: The case of wood." Environmental Impact Assessment Review 37: Levasseur, A., P. Lesage, et al. (2012). "Assessing temporary carbon sequestration and storage projects through land use, land-use change and forestry: Comparison of dynamic life cycle assessment with ton-year approaches." Climatic Change 115(3-4): Levasseur, A., P. Lesage, et al. (2013). "Biogenic Carbon and Temporary Storage Addressed with Dynamic Life Cycle Assessment." Journal of Industrial Ecology 17(1): Zanchi, G., N. Pena, et al. (2012). "Is woody bioenergy carbon neutral? A comparative assessment of emissions from consumption of woody bioenergy and fossil fuel." GCB Bioenergy 4(6):

47 NON-CARBON CLIMATE EFFECTS FROM BIOMASS 47

48 There is more than carbon, when we speak about biomass and climate change Source: IPCC, AR5, Phys. Sci. Bas., Chapt.8

49 Site-specific global warming potentials of biogenic CO2 for bioenergy: contributions from carbon fluxes and albedo dynamics (Cherubini 2012)

50 Historical perspective on Albedo change over time Source: IPCC, AR5, Phys. Sci. Bas., Chapt.8 50

51 Exercise 3 Objectives Model the emissions (CO2) over time of: all processes, cumulated emissions Apply a discounting rate (rate is your choice, please motivate your choice) Evaluate climate effects from biogenic carbon emissions using GWPbio factors (consider storage time for flow BC) Compare your best and worst case scenarios from the Ex 1&2 Discuss the above results Identify key factors to reduce the environmental impacts of the system Give recommendations for the environmental use of wood Data Carbon emissions (fossil + biogenic) GWPbio factors depending on storage time 51