Section 096-167-5 - Net GHG emissions estimatesA.Categories. Estimates of net GHG emissions in Maine shall include estimates of emissions and sequestration from the following categories: (1) Fossil fuels. Fossil fuel emissions shall be estimated in accordance with section 4. A.(2)(a)(ii) (CO2 from fossil fuel combustion) of this Chapter and reported by the following sectors: transportation, residential, industrial, electric power, and commercial.(2) Waste. Emissions from waste shall be estimated in accordance with sections 4. A.(2)(a)(ix) (Municipal solid waste), 4. A.(2)(a)(xi) (Wastewater), and 4.A.(3)(c) (Solid waste) of this Chapter.(3) Forests (live biomass, dead biomass, and soils)(a) Acreage data shall be obtained from the USGS National Land Cover Database (NLCD).(b) Aboveground forest carbon data shall be obtained from the USDA Forest Service Forest Inventory and Analysis database (FIA). Fluxes shall be calculated as the difference in stock inventories between the first and last years of the analysis window. Carbon estimation methods shall follow those outlined in Annex 3 of the EPA's "Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2017" as published by EPA in 2019. The methods in this Annex 3 are incorporated by reference herein. NOTE: The incorporated material can be accessed at www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2017, and copies of the incorporated material are also available from the Department by calling (207) 287-2235.
(c) Soils data shall be obtained from the USDA Natural Resources Conservation Service SSURGO soils database. Soil fluxes shall be calculated as differences in soil carbon stock by land use change between the first and last years of the analysis window based on the NLCD.(d) When the 'forest floor' data from the FIA partially includes the SSURGO total soil measurements, the FIA forest floor carbon estimates shall be subtracted from the total SSURGO soil carbon estimates in forest soil carbon stock difference calculations.(e) Shrubland non-soil component estimates shall be included in the aboveground forestland estimates.(4) Wood products (sawlogs, pulp, and landfilled). Sequestration of carbon in forest products shall be estimated based on timber flows (harvest minus export plus import) from the Maine Forest Service Annual Wood Processing Reports. Processed wood shall be divided into sawlogs, pulp logs, biomass, and fuelwood. The longevity of the products made from these four wood types shall be applied based on factors in the USFS For GATE Tool, which estimates wood product decay and deposition into landfills. Processed wood that could be utilized outside of Maine (i.e., exports) and wood processed elsewhere that could be utilized in Maine (i.e., imports) shall not be considered in this assessment.(5) Wetlands (biomass and soils) (a) Non-woody wetland soil carbon shall be estimated by:(i) Using data from a direct monitoring network for non-woody wetland fluxes in Maine; or(ii) Taking the non-woody wetland land use data from the NLCD database representing the first and last year of the analysis window years and assigning a carbon value from the SSURGO database. Changes in land area by non-woody wetland soil type over time shall be used to estimate fluxes. (b) Woody wetlands, including forested swamps and shrub swamps, shall be accounted for in the forest estimates.(6) Agriculture (emissions and soils) (a) Emissions from agricultural activities shall be estimated in accordance with section 4.A.(2)(a)(i)(Agriculture) of this Chapter.(b) Accounting for agricultural soil carbon from changes in farm practices may be included if the Department determines that an available data source and methodology are sufficiently representative of activities in Maine.(7) Urban (biomass and soils) (a) Urban aboveground biomass carbon shall be based on the forest stock change from the FIA database. (b) Urban soil carbon estimates shall be based on NLCD land use data that includes developed lands with different intensities ranging from open space to low, medium, and high intensity with the associated soil carbon data for the urban land use change from the SSURGO database.(8) Inland waters (sedimentation). Inland water carbon estimates shall be based on the amount of carbon delivered to the ocean at the mouth of a river. Specifically, this is the transport of dissolved organic carbon from watersheds through surface waters (e.g., lakes and streams) to rivers and exported to the ocean. (This estimate shall not include dissolved inorganic carbon.) A preliminary estimate of 20% shall be assumed to represent the amount of dissolved organic carbon delivered to the ocean that is then sequestered by sedimentation, with the rest assumed to be lost to photo-oxidation and decomposition back to the atmosphere.(9) Coastal waters (sedimentation and biomass; blue carbon) (a) Blue carbon stock and flux estimates for salt marshes shall be based on: (i) Total salt marsh area as reported in the most recent Maine Tidal Marshes Map produced by the Department of Agriculture, Conservation and Forestry, Maine Natural Areas Program.(ii) The average carbon density over the upper 1 meter.(iii) The average burial rate flux for coastal marsh sediments.(b) Blue carbon stock and flux estimates for eelgrass shall be based on:(i) The eelgrass meadow area determined by the State of Maine agencies and partners eelgrass surveys (e.g., Maine Department of Environmental Protection, Maine Department of Marine Resources, and partner mapping efforts where quality assurance is known an accepted by Department staff).(ii) The average carbon density over the upper 1 meter.(iii) The average burial rate flux for eelgrass beds.(c) Carbon stocks shall be calculated by multiplying the ecosystem area in square meters by the carbon density of a one-square-meter area. Carbon fluxes shall be calculated by multiplying the ecosystem area by the burial rate.B.Calculations of net GHG emissions(1) Carbon emitted and sequestered shall be calculated for each of the categories in section 5A, above. The difference between emission and sequestration from these categories shall provide an estimate of net carbon emissions over the defined analysis window.(2) For conversions of carbon to CO2e, CO2e shall be assumed equal to the molecular weight of CO2 (44) divided by the atomic weight of carbon (12) times the elemental carbon.(3) Final net GHG emissions shall be compared to the Maine goal of carbon neutrality by 2045 and reported for all years in the period of 1990-2045 for which the data identified in section 5A above are available.06-096 C.M.R. ch. 167, § 5