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Inventory Methodology

Inventory Methodology. September 29, 2009. Presentation Overview. Emission Inventory Overview Calculating Indirect Emissions from Electricity Use Calculating Direct Emissions from Mobile Combustion Calculating Direct Emissions from Stationary Combustion Water Utility Emissions Sources

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Inventory Methodology

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  1. Inventory Methodology September 29, 2009

  2. Presentation Overview • Emission Inventory Overview • Calculating Indirect Emissions from Electricity Use • Calculating Direct Emissions from Mobile Combustion • Calculating Direct Emissions from Stationary Combustion • Water Utility Emissions Sources • Data Management

  3. Emission Inventory Overview

  4. GHG Accounting Three potential methods for quantifying particular emissions: • Direct measurement – relatively uncommon, largely limited to use of continuous emission monitoring systems (CEMS) installed to measure other pollutants, in particular for NOX and SOX from power plants • Use of “activity data”, or measured surrogate parameters, combined with standard or specific emission factors. • Examples of activity data: • Natural gas and electricity consumption measured by meter and reported on utility bills • Gasoline consumption from purchase records or estimated from vehicle odometer readings and fuel efficiency data • Examples of emission factors: • Carbon content and CO2 from combustion of natural gas do not vary significantly between suppliers when gas is measured on a Btu basis – thus published emission factors can accurately represent emissions • Accurate records exist as to the GHG emission intensity of grid electrical power in various regions of the country • Mass balance (HFCs, PFCs, SF6) • Activity Data = Purchase records, maintenance records

  5. GHG Accounting • Key Scope 1 & Scope 2 Source Categories for Water Utilities • Stationary combustion • Mobile combustion • Electricity purchase • Scope 1 Source Types Examined in Water Research Foundation Study: • N2O from ozone generation • GAC regeneration • Emission impacts of land use • Methane from water storage reservoirs • Sludge decomposition • Biological denitrification • Scope 3 Emissions • Plans to examine benefits of external projects or impacts of upstream/downstream may drive needs for other quantification methodologies

  6. Calculating Indirect Emissions from Electricity Use

  7. Electricity Purchases - Overview Emissions from Electricity Purchases: • Primarily associated with fossil-fuel fired generation • CO2 (> 95% of impact) • CH4, N2O byproducts must be included • Coal generation generally produces highest emissions (with various ranks of coal producing different impacts), followed first by liquid fuels then by natural gas • Hydro, nuclear, renewable power generally produce “zero emission” power • For purchased electricity, information is therefore needed on either utility-specific or grid-average characteristics of power supplied

  8. Process for Estimating Purchased Electricity Emissions • Select Emission Factors • May be supplied from electric utility if available • Otherwise, protocols generally recommend use of “eGRID” database for domestic power. Availability of eGRID data generally lags several years, so use most recent year available • Determine Annual Electricity Consumption and Calculate GHGs per water utility sector • Convert to CO2 equivalent emissions

  9. USEPA’s eGRID Power Pool Regions

  10. Example Emission Factor Table by eGRID Subregion

  11. Example: Electricity Use • Facility in Washington used 22,100 MWH of electricity in 2004. • Calculate the Scope 2 indirect emissions associated with this electricity use.

  12. Example: Electricity Use1. Select Emission Factors • Emissions Factors are geography specific • For Washington, use eGRID subregion NWPP – WECC Northwest: • 921.10 lb CO2/MWH • 0.022 lb CH4/MWH • 0.014 lb N2O/MWH • Source: TCR Table 14.1

  13. Example: Electricity Use2. Determine Annual Consumption and Calculate GHGs Emissions Factor • CO2 Emissions = 921.10 lb/MWH * 22,100 MWH/yr / 2204 lb/metric ton = 9,240 metric tons/ yr • CH4 Emissions = 0.022 lb/MWH * 22,100 MWH/yr / 2204 lb/metric ton = 0.22 metric tons/ yr • N2O Emissions = 0.014 lb/MWH * 22,100 MWH/yr / 2204 lb/metric ton = 0.14 metric tons/ yr • Source: TCR Table 14.1 Annual Electricity Consumption Unit Conversion

  14. Example: Electricity Use3. Convert all emissions to CO2 Equivalents • CO2 Emissions: 9,240 metric tons/yr of CO2 (already calculated) • CH4 Emissions: CH4 has a GWP of 21 (21 times more effective GHG than CO2) • CO2 equivalent emissions = 0.22 metric tons/yr * 21 = 4.6 metric tons/yr • N2O Emissions N2O has a GWP of 310 (310 times more effective GHG than CO2) • CO2 equivalent emissions = 0.14 metric tons/yr * 310 = 43.4 metric tons/yr Total CO2 equivalent emissions= 9,240 mt/yr + 4.6 mt/yr + 43.4 mt/yr = 9,288 mt/yr

  15. Calculating Direct Emissions from Mobile Combustion

  16. Mobile Source Emissions - Overview • Mobile sources emit CO2, CH4, and N2O • CO2 emissions depend only on characteristics and quantity of fuel – type of vehicle not a factor • CH4 and N2O emissions depend on fuel type and vehicle vintage and pollution control technology and are generally estimated based on miles driven (These are usually small fractions of total CO2-e) • Thus need estimates of both fuel quantity and mileage. Where one but both does not exist, vehicle-specific fuel economy estimates can be obtained from www.fueleconomy.gov

  17. Process for CO2: Mobile Combustion • Does your utility have Fuel Consumption Data? • Directly Proportional to Fuel Consumption • Identify total annual fuel consumption by fuel type, and approx split between city/highway driving. • Total Fuel Use (gallons) = Total Mileage (miles) / • (Fuel Economy City (mpg) x 55% + Fuel Economy Highway (mpg) x 45%) • Calculate metric tons of CO2. • Total Emissions (metric tons) = Fuel Consumed (gallons) xEmission Factor (kg CO2/gallon) x 0.001 metric tons/kg • Does your utility have Mileage Data only? • Requires list of vehicle types

  18. Process for CH4 and N2O: Mobile Combustion Dependent on Engine and Pollution Control Technology – Can be Listed by Emission Control “Tier” or by Year and Type of Vehicle • Identify the vehicle types, fuel, and model years of all vehicles owned and operated. • Identify the annual mileage by vehicle type. • Select the appropriate emission factor for each vehicle and fuel from program specific guidance (for example, Table 13.4 from the General Reporting Protocol, TCR). • Calculate each vehicle type CH4 and N2O emissions and convert to metric tons. • Sum the emissions over each vehicle and fuel type. • Convert CH4 and N2O emissions to CO2‑e. • Total CO2‑e emissions from mobile combustion.

  19. Example: Mobile Combustion1. Vehicle Inventory Understand Your Vehicle Inventory: This example focuses on passenger cars, though a typical vehicle inventory would include other vehicle types in addition.

  20. Example: Mobile Combustion2. Fuel Consumption What is your Annual Fuel Usage for this Vehicle Type? • Beginning of Year: 20,000 gallons of motor gasoline in stock • Purchased: 235,000 gallons of motor gasoline • End of Year: 10,000 gallons of motor gasoline in stock • Fuel consumption = 20,000+235,000-10,000 = 245,000 gallons used/year

  21. Example: Mobile Combustion3. Select Emission Factors & Calculate CO2 Emissions • TCR Table 13.1 emission factors for motor gasoline: • 8.81 kg CO2/gallon • CO2 Emissions = 8.81 kg/gallon * 245,000 gallons/yr / 1000 kg/metric ton = 2,158 metric tons/ yr

  22. Example: Mobile Combustion4. Emissions Calculations for CH4 and N2O • Total Mileage = 245,000 gallons x (20 mpg x 55% + 25 mpg x 45%) = 5,451,250 miles • CH4 Emissions (metric tons) = 0.0178 g/mi x 5,541,250 (mi) x 0.000001 metric tons/g = .099 metric tons CH4 • N2O Emissions (metric tons) = 0.0273 g/mi x 5,541,250 (mi) x 0.000001 metric tons/g = .151 metric tons N2O

  23. Example: Mobile CombustionConvert to CO2 Equivalent • CO2 Emissions: 2,158 metric tons/ yr (already calculated) • CH4 Emissions: CH4 has a GWP of 21 (21 times more effective GHG than CO2) • CO2 equivalent emissions = .099 metric tons/yr * 21 = 2.1 metric tons/yr • N2O Emissions: N2O has a GWP of 310 (310 times more effective GHG than CO2) • CO2 equivalent emissions = 0.151 metric tons/yr * 310 = 46.8 metric tons/yr • Total CO2 equivalent emissions= 2,158 mt/yr + 2.1 mt/yr + 46.8 mt/yr = 2,207 mt/yr

  24. Notes Regarding Biofuels • Biofuels (ethanol, biodiesel) generally quantified as zero emission for end user. See specific protocol • Based on continued debate regarding life cycle impacts of some biofuel production, use caution regarding this assumption. Impacts of production likely will continued to be applied to producer, but use of these fuels will not necessarily mean zero life cycle impacts

  25. Calculating Direct Emissions from Stationary Combustion

  26. Process for Estimating: Stationary Combustion • Identify all types of fuel directly combusted as part of operations. • Determine the annual consumption of each type of fuel. • Select the appropriate emission factor for each fuel. • Calculate the CO2 emissions for each fuel and convert to metric tons. • Calculate the CH4 and N2O emissions for each fuel and convert to metric tons. • Convert CH4 and N2O emissions to CO2-e and sum all subtotals.

  27. Example: Stationary Combustion Emissions • Stationary Combustion • Natural Gas used for space heating • 788,400 MMBtu of natural gas used in one year

  28. Example: Stationary Combustion1. Select Emission Factors • TCR emission factors for natural gas are as follows: • 53.06 kg CO2/MMBTU • 0.1 g N2O/MMBTU • 5 g CH4/MMBTU • Source: TCR Tables 12.1 and 12.9 • The CO2 value reflects an unspecified, weighted US average of heat content for natural gas, and default emission factors for N2O and CH4.

  29. Example: Stationary Combustion2. Emission Calculations • CO2 Emissions = 53.06 kg/MMBTU * 788,400 MMBTU/yr / 1,000 kg/metric ton = 41,833 metric tons/ yr • N2O Emissions = 0.1 g/MMBTU * 788,400 MMBTU/yr / 1,000,000 g/metric ton = 0.08 metric tons/ yr • CH4 Emissions = 5 g/MMBTU * 788,400 MMBTU/yr / 1,000,000 g/metric ton = 3.9 metric tons/ yr

  30. Example:3. Convert to CO2 Equivalent • N2O has a GWP of 310 (310 times more effective GHG than CO2) • CO2 equivalent emissions = 0.08 metric tons/yr * 310 = 24.8 metric tons/yr • CH4 has a GWP of 21 (21 times more effective GHG than CO2) • CO2 equivalent emissions = 3.9 metric tons/yr * 21 = 81.9 metric tons/yr • Total CO2 equivalent emissions= 41,833 mt/yr + 24.8 mt/yr + 81.9 mt/yr = 41,940 mt/yr

  31. Water Utility Emission Sources

  32. Data Organization: Six Water Utility Sectors Inventory baselines are more meaningful if organized congruently with typical water utility functionality: • Source • Treatment • Distribution • Buildings/Infrastructure • Fleet • Other

  33. Data Management

  34. Granularity of Data • Equipment Level Data • Best Data if available • Decreases the number of assumptions • Allows for better understanding of opportunities • Grouped Sources within the same category • Examples are Emergency generators, gasoline trucks • Data is often maintained at the facility level but sometimes at the corporate level • Bulk Data • Examples are total fuel purchased by fuel type or total electricity purchased • Grosser Assumptions will have to be made INCREASING GRANULARITY

  35. Environmental Data Management (EDM) • Systems • Paper Data forms collected by an inventory manager • Spreadsheet tools • A Variety of Commercial Software Tools • Selection Factor for the Type of System • Data volume • Number of Data Sources • Number of Personnel Involved • Existing Use of Data Management Tools

  36. Data Security • User Identification and Password • Departmental accessibility via the Intranet • Access/Write Protection to ensure data cannot be accidentally modified

  37. Data Collection Frequency • Collect data daily or monthly by the respective departments • More frequent collection and analysis can be helpful to understand progress toward reduction goal • Compiled at Least Annually

  38. Quality Assurance • Activity data must match meter reading records, utility invoices, or other source records • Unit Conversions • Use of Current Emission Factors • Calculation Methodology • Summation of equipment of facility-level

  39. Data Quality- Common Methods to Improve/ Maintain Quality • Minimize manual entry of data • Comparison of year to year data • Data are used for other regulatory reporting purposes; and thus QC’d as part of that program • Comparison of annual data to a production index • Compare total numbers to summaries from meter readings/ utility company/ other facility totals/ etc. • Compare relative emissions between facilities- does the data make sense in relation to size of the facility?

  40. Base Year • TCR: First year of complete GHG reporting • Shifts if organization changes result in emissions of >5% (CCAR > 10%) • Hydrologic conditions will impact the inventory magnitude • Drier years could result in increased pumping

  41. Adjustment Procedures • Structural • Avoid artificial increases or decreases in emissions • Insourcing • Outsourcing • Organic growth (e.g. decrease in throughput): No adjustments will be made. • Methodology • TCR; if >5% emissions for overall total or one source category • Correction of Errors • Threshold for revision and re-reporting • Wrong Emission Factor • Inaccurate Assumptions • Incorrect Unit Conversions • Quantification Errors

  42. Roles and Responsibilities • Support of top-level organizational management • Inventory Manager • Listing of Entity Staff Consulted

  43. Employee Training

  44. Internal Audits • Identify gaps and errors prior to reporting • Conducted by someone familiar with GHG accounting and reporting principles and the protocol used but not involved in the inventory development process. • Assign corrective actions with a timeframe

  45. External Verification • Credibility of the GHG emissions inventory • Conducted by parties not involved with the development of the inventory • TCR requires third-party verification of all emission reports • USEPA may not require it • Ecology has indicated that it will be required once a cap and trade system is in place

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