MRV Document 2 of 2: Technical Specifications for the Emissions Calculator

Transcription

1 MRV Document 2 of 2: Technical Specifications for the Emissions Calculator The purpose of this document is to provide a transparent explanation for the process used to calculate greenhouse gas (GHG) emissions in the Carbon Benefits Project (CBP) Emissions Calculator, an internal component within the CBP Landscape Carbon MRV System. It is a technical companion to the more general MRV User Guide (MRV Document 1 of 2). Accounting Principles and Methods The Emissions Calculator follows the guidelines on greenhouse gas accounting published by the Intergovernmental Panel on Climate Change (IPCC, 2003; IPCC, 2006a; IPCC, 2006b). Emissions or removals of carbon dioxide (CO 2 ) can be calculated using the stock-difference method or the annual gainloss method and then converted to units of carbon dioxide by multiplying by 44/12. The Emissions Calculator primarily uses the stock-difference method of accounting to calculate the emissions and removals of carbon dioxide in agriculture, forestry and other land uses (AFOLU) by measuring the change between terrestrial carbon stocks at two or more time periods (see Equation 1 below). The carbon stocks in the Emissions Calculator are defined for each land cover and at specific time period after the initial start year of the project. The carbon stocks can be based on direct inventory measurements and/or process models. C = (C T2 C T1 ) / (T 2 T 1 ) (Equation 1) Where C = the annual change in carbon stocks for an identical parcel of land, tonnes C/yr C T1 = the carbon stocks at time = 1, tonnes C C T2 = the carbon stocks at time = 2, tonnes C The Emissions Calculator does also incorporate some aspects of the annual gain-loss accounting method (see Equation 2 below). The gain-loss method is a process based approach that balances additions and removals from a starting carbon stock. Note that when the stock-difference method is reported annually it approximates the gain-loss method. The Emissions Calculator uses growth rates for forest stands to estimate the annual gains to the above and below ground biomass pools. C = C gain - C loss (Equation 2) Where C = the annual change in carbon stocks, tonnes C/yr C gain = the annual addition to the carbon stocks, tonnes C/yr C loss = the annual removals from the carbon stocks, tonnes C/yr Emissions or removals of non-carbon dioxide gases are typically calculated using activity data and emission factors (see Equation 3 below). Activity data measure the magnitude of human influence and for landscape carbon are typically the land area extent in hectares (but also could be number of animals in agricultural systems, etc). Emissions factors describe the emission of a specific non-co 2 gas per unit of activity data. The Emissions Calculator uses activity data and emission factors to calculate the non- CO 2 emissions from biomass burning and some agricultural practices. Several emission factors are required parameters for defining land covers in the Emissions Calculator. non-co 2 emissions = activity data x emissions factor (Equation 3) 1

2 A reduction of terrestrial carbon stocks is an emission of greenhouse gases to the atmosphere while an increase in terrestrial carbon stocks is a removal from the atmosphere (sequestration). The Emissions Calculator reports the annual stocks for six IPCC terrestrial carbon pools: above ground biomass, below ground biomass, dead wood, litter, soil organic carbon, and also harvested wood products. As these carbon pools change from year to year, CO 2 and non-co 2 greenhouse gases are emitted to and removed from the atmospheric pool of GHGs. The Emissions Calculator computes initial and final carbon stocks in each of the terrestrial carbon pools for the parcel in both the reference and project scenario. Changes in carbon stocks are often reported on an annual basis but sometimes committed emissions are reported in the first year following a change for the entire time period of analysis. GHG emissions and removals are reported as changes occur in the initial and final stocks for that parcel in both of its scenarios. GHG emissions include both CO 2 and non- CO 2 gases. GHG emissions and removals attributed to the project are calculated by subtracting the reference scenario emissions from the project scenario emissions. [Note that the current version of the Emissions Calculator as of March 2013 converts tonnes of carbon into tonnes of carbon dioxide equivalents by a factor of 3.67 rather than 44/12 ( ) so there are some rounding errors in the tco 2 e values.] Pre-Loaded Default Values for Tier 1 The Emissions Calculator computes carbon stocks by multiplying the activity data (typically the land area) of a parcel by the emission factors (typically the carbon density) of the land covers that describe and define that parcel. The land area (in units of hectares) of the parcel is always provided directly by the user when defining a parcel of land to evaluate. The user has several options regarding the emission factors used to calculate carbon stocks and perform GHG calculations. First, users can use the preloaded Tier 1 global default values for emission factors that define land covers throughout the world. The pre-loaded default values made available to the user in the Emissions Calculator are taken from the various tables in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Volume 4 Agriculture, Forestry and Other Land Use (IPCC, 2006b) as organized and implemented in the Ex-Ante Carbon Balance Tool (EX-ACT version 3.1.2) developed by the Food and Agriculture Organization of the United Nations (FAO, 2011). These tables provide a Tier 1 estimate of carbon stocks in multiple carbon pools and other emission factors according to climate and ecosystem throughout the world. Examples of common tables adapted from the 2006 IPCC Guidelines include Table 2.2: Litter and Deadwood Carbon Stocks, Table 2.3: Soil Organic Carbon Stocks, Table 4.7: Above-Ground Biomass in Natural Forests, Table 4.8: Above-Ground Biomass in Plantations, Table 4.9: Above-Ground Biomass Growth Rates in Natural Forests, and Table 4.10: Above-Ground Net Biomass Growth Rates in Tropical and Sub-Tropical Forest Plantations (IPCC, 2006b). A complete and transparent listing of all of the more than 1,500 preloaded default values for all of the parameters and land covers is available for download in an Excel spreadsheet hosted on the Landscape Carbon MRV System Help page. Modifying Tier 1 Emission Factor Values There is a second option for defining the emission factors that describe each land cover in the Emissions Calculator. Sometimes the IPCC publishes an acceptable range of Tier 1 global emission factors for a parameter (ie. 160 to 430 tdm/ha in an African tropical moist deciduous forest) or may provide two different methods (ie. annual growth rates or expected biomass stocks for a forest). Users also have the flexibility to modify one or more default values to another reasonable and defensible IPCC Tier 1 default value. Users can modify one or more parameter in the pre-loaded land covers or develop a new land cover based on other appropriate IPCC Tier 1 data. 2

3 Tier 2 Emission Factor Values A third option for users of the Emissions Calculator is to provide Tier 2 national data to define the emission factors used to compute carbon stocks. If national data are available for important parameters, users can define a land cover to compute carbon stocks that reflect national rather than global emission factors. It is permissible to use multiple sources of data when defining a land cover. Users should document their data sources to confirm that their GHG estimates are conservative and verifiable. National data sources might include national forest inventories or national soil surveys. Tier 3 Emission Factor Values Finally, the emission factors used to define a land cover and compute carbon stocks can be custom defined by the user based on actual measurements and inventory data of carbon stocks collected in the project area. These new data should be the results of field inventories that directly measure some or all of the five major carbon pools (above ground biomass, below ground biomass, litter, dead wood, soil organic matter) in the project area. These Tier 3 data may also be values from published literature from nearby projects or research studies. The Online Landscape Carbon MRV provides resources for users to plan and implement a measurement effort and also tools for users to store and analyze inventory data. These data can then be passed into the Emissions Calculator to define custom land covers based on Tier 3 emission factors. The Emissions Calculator provides flexibility and transparency by displaying and allowing modification of all data and parameters that define land covers. Detailed Explanation of Calculations The calculations performed within the Emissions Calculator are a function of the inputs provided by the user in defining project location, project length, land covers, and two opposing scenarios. The location of the project influences the default land cover values that are matched to the regional ecosystem and climate. The length of the project determines how many years the calculator estimates carbon stocks and GHG emissions. The selection of default land covers or the creation of unique Tier 3 land covers defines the emission factors for that parcel and the resulting GHG emissions from land cover change. The user defines both a reference scenario and a project scenario that include several parameters that all influence the sequestration or emission of GHGs as a result of land cover change in a project. Project Description The user defines several parameters on the Project Description section that influence the calculation of GHG emissions (see Figure 1 below). The Duration of the project determines how many years the calculator computes carbon stocks and GHG emissions. The length of the project impacts net GHG emissions as a very long project may eventually sequester enough GHGs through forest re-growth to more than offset a large emission from deforestation or degradation in the first year of a project. The Emissions Calculator also uses twenty years as a transition point for reaching a new soil organic carbon stock equilibrium and also as the dividing point between young (fast) and old (slow) growth rates for forest biomass growth. 3

4 Figure 1. Example of a Project description page in the Emissions Calculator. The Continent, Climate Zone, and Moisture Zone identified in the drop down menus will influence the selection of Tier 1 default land covers that are made available to the user to define the emission factors for the parcels and scenarios for the project. The Soil Type selected in the drop down menu will influence values of the soil organic carbon (SOC) stocks in the Tier 1 default land covers made available to the user. HAC is high activity clay and LAC is low activity clay. The SOC stocks used in the Emissions Calculator are adapted from Table 2.3 in the 2006 IPCC Guidelines (IPCC, 2006b). Users can manually modify Tier 1 SOC stocks in a land cover based on the IPCC stock change factors due to land use, management, and inputs for cropland (Table 5.5) or grassland (Table 6.2). The Carbon/Dry Matter ratio is set at the IPCC default value of 47% carbon in dry woody biomass. However, the user may revise this ratio by entering another value to define the carbon percentage of dry woody biomass. Altering the Carbon/Dry Matter ratio here will greatly influence the carbon stocks in live biomass for a land cover. Parcel Definition The user defines several parameters on the Parcel Description section that influence the calculation of GHG emissions. The Area of a parcel (in hectares) is the activity data used to calculate carbon stocks for that parcel by multiplying it times the emission factor. The emission factors used in the calculations are determined by the parameters in the Land Cover selected by the user whether those parameters are populated by pre-loaded Tier 1 default values, modified Tier 1 values, national Tier 2 data, or Tier 3 data derived from project measurements and inventories. Users either use or modify an existing land cover or create an entirely new land cover by adding a new land cover populated with project measurement data or other appropriate data sources (see Figure 2 below). 4

5 Figure 2. Example of a Parcel definition page. Reference Scenario and Project Scenario The user defines several parameters when describing the two scenarios that all influence the calculation of carbon stocks and GHG emissions. The calculations are performed in the same manner for both a Reference Scenario and a Project Scenario. Each scenario is independently defined. Both scenarios should use similar data sources for inputs to ensure conservative and reasonable estimates. The Emissions Calculator also reports the difference between the Reference and Project Scenarios to report the GHG emissions or removals attributed to the project. Users may also add multiple subsequent land cover changes within a single scenario to show additional changes that occur later in the project time period on the same parcel of land. 5

6 Figure 3. Example of a Reference Scenario definition page. Land Cover. The selection of the land cover determines the emission factors that calculate carbon stocks and GHG emissions (see Figure 4 below). All land covers, whether populated with Tier 1 default values, Tier 2 national data, or Tier 3 local measurement values, are defined by values that describe the five primary terrestrial carbon pools, the impacts of burning biomass, forest growth rates, and the ratio of above and below ground biomass. Young and old forest growth rates are defined as less than 20 years old and greater than 20 years old respectively. Forest biomass grows according to the defined growth rates but a maximum biomass is capped at the biomass levels used to define the land cover rather than allowing the forest to grow indefinitely in long project durations past a reasonable biomass level for that ecosystem. Users can modify either the growth rate or the biomass stocks in relation to the project time length to calculate desired carbon stocks. 6

7 Figure 4. Example of a Land Cover definition page. Start Year. The selection of the start year is only applicable for scenarios with multiple land cover changes within the time period of the project. The start year of the first land cover change should be left at zero or else the Emissions Calculator may generate an error message ( unhandled exception ). GHGs are emitted or removed as a result of stock differences in the year following the year identified as the start year for that land cover change. Start year is provided as a positive integer (ie. 1-30) rather than the calendar year when the change occurs (ie ). Degradation. Entering a value other than zero in the % Degradation reduces the carbon stocks in the following year by that percentage. Forest carbon stocks then begin to grow in the second year following degradation as the forest recovers from the disturbance. Forest growth is determined by the growth rates defined in the land cover. Unless the user adds local measurement data to define the young and old growth rates, the Tier 1 default growth rates are taken from Tables 4.9 and 4.10 in the 2006 IPCC Guidelines (IPCC, 2006b). For projects with very long durations, the forest is not allowed to grow past the maximum biomass stocks as defined in the land cover. Dead wood and litter stocks are degraded by the given percentage but do not recover. Soil organic carbon stocks degrade over a twenty year period from the initial stock to the degraded stock level. Harvested Wood Products. When a forest is converted to non-forest or degraded to lower carbon stocks, users may set aside some of the forest biomass into long term storage in a harvested wood products (HWP) pool. Users define how many tonnes of dry matter are set aside. The entire HWP pool is set aside in the first year and remains stable (unchanged) throughout the duration of the project. 7

8 Burned. If the user selects Burned, the Emissions Calculator estimates the amount of greenhouse gases emitted to the atmosphere from burning biomass following land cover change in year 1. Several parameters used to define a land cover (% dry matter released, CH 4 released, and N 2 O released) determine the amount of GHGs emitted to the atmosphere. The GHG calculations for burning are based on values taken from Tables 2.4, 2.5, and 2.6 in the 2006 IPCC Guidelines (IPCC, 2006b). Practice. The Practice describes the potential mitigation affects of implementing common agricultural practices on agricultural land cover. These values to describe the mitigation potential are in units of tco 2 e/ha/yr and range from 0.15 to Potential agricultural practices that have GHG mitigation potential include improved agronomic practices, nutrient management, tillage and residues management, water management, manure application, and agroforestry. The default practices perform GHG calculations, primarily on the soil organic carbon stocks, that are based on values adapted from Table 8.4 in the Fourth Assessment Report (IPCC, 2007). Users may choose the specific practices that occur in the project area or select Default where no practices are applied to the calculations. Figure 5. Example of a Practices definition page. Emissions Tables for Reference and Project Scenarios The Emissions Calculator reports GHG emissions for both the Reference Scenario and Project Scenarios in separate tables that show annual terrestrial carbon stocks and both CO 2 and non-co 2 emissions to and removals from the atmospheric GHG pool (see Figure 6 below). The atmosphere pool shows cumulative GHGs rather than annual changes. This full reporting of annual stocks and GHG fluxes for both scenarios is intended to provide complete and transparent reporting of results. Users can verify and reproduce similar GHG emission estimates by replicating the calculations offline in a spreadsheet of their own design or by using the EX-ACT tool (FAO, 2011) using similar inputs. 8

9 Figure 6. Emissions Table for a Reference Scenario. 9

10 Database Tables within the Emissions Calculator The Emissions Calculator is written in Django and the front end html web pages are driven by multiple database tables. The overview of all tables within the Emissions Calculator is given below in Table 1. As stated previously, the tables within the Emissions Calculator are populated by values from the 2006 IPCC National Guidelines on Greenhouse Gas Inventories (IPCC, 2006b) as organized and implemented in the Ex-Ante Carbon Balance Tool (EX-ACT version 3.1.2) developed by the Food and Agriculture Organization of the United Nations (FAO, 2011). This document does not provide an exhaustive listing of the many hundreds of rows of data that define the multiple parameters but instead will show screenshots of the partial Django tables. A complete listing of all of the more than 1,500 values for all of the parameters is available for download in an Excel spreadsheet hosted on the Landscape Carbon MRV System Help page. Table 1. Emissions Calculator Database Tables 10

11 Table 2. AbovegroundBiomass Table 3. BelowgroundRatio 11

12 Table 4. BiomassLandUse Table 5. Carbonpools 12

13 Table 6. Combustion Factor Table 7. Combustionlanduse Table 8. Grasslandbiomass 13

14 Table 9. Grasslandsoil Table 10. Landcover 14

15 Table 11. Landuse Table 12. Necromass Table 13. Parcels 15

16 Table 14. Practices Table 15. Projects 16

17 Table 16. RiceEmission Table 17. RicePractice 17

18 Table 18. Scenarios Table 19. SoilCarbonFactor 18

19 Table 20. SoilCarbonRef 19

20 References FAO ExACT Version released March IPCC Good Practice Guidance for land Use, Land-Use Change and Forestry. Penman, J., Gytarsky, M., Hiraishi, T., Krug, T., Kruger, D., Pipatti, R., Buendia, L., Miwa, K., Ngara, T., Tanabe, K., and Wagner, F. IGES, Japan. IPCC. 2006a IPCC Guidelines for National Greenhouse Gas Inventories. Volume 1: General Guidance and Reporting. Prepared by the National Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds). IGES, Japan. IPCC. 2006b IPCC Guidelines for National Greenhouse Gas Inventories. Volume 4: Agriculture, Forestry and Other Land Use. Eggleston, H.S., Buendia, L., Ngara, T., and Tanabe, K. (eds). IGES, Japan. IPCC Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 20

21 For more information, contact: Mike Smalligan Patrick Paul Research Forester Research Programmer Michigan State University Michigan State University Global Observatory for Ecosystem Services Global Observatory for Ecosystem Services 1405 South Harrison, Suite South Harrison, Suite 101 East Lansing, Michigan USA East Lansing, Michigan USA Phone: (517) Phone: (517) Rob Braswell Matt Hanson Senior Research Scientist Imaging Scientist Applied GeoSolutions Inc. Applied GeoSolutions Inc. 87 Packers Falls Road 87 Packers Falls Road Durham, NH Durham, NH Phone: (603) Phone: (603)