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 Data Management

Emission Inventory Overview

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

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

Calculating Indirect Emissions from Electricity Use

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

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

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USEPA’s eGRID Power Pool Regions

Example Emission Factor Table by eGRID Subregion

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.

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

Example: Electricity Use2. Determine Annual Consumption and Calculate GHGs

• 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

Emissions FactorAnnual Electricity Consumption

Unit Conversion

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

Calculating Direct Emissions from Mobile Combustion

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

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

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

1.Identify the vehicle types, fuel, and model years of all vehicles owned and operated.

2.Identify the annual mileage by vehicle type.3.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).

4.Calculate each vehicle type CH4 and N2O emissions and convert to metric tons.

5.Sum the emissions over each vehicle and fuel type.

6.Convert CH4 and N2O emissions to CO2‑e.

7.Total CO2‑e emissions from mobile combustion.

Example: Mobile Combustion1. Vehicle Inventory

Number of Vehicles Model Year Vehicle Type

200 2000 Passenger cars

Understand Your Vehicle Inventory:

This example focuses on passenger cars, though a typical vehicle inventory would include other vehicle

types in addition.

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

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

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

Example emission factors for each fuel and vehicle type

Vehicle type Fuel Model year

Methane (CH4)

(g/mi)

Nitrous oxide (N2O)

(g/mi)

Passenger cars Motor gasoline 2000 0.0178 0.0273

Source: TCR General Reporting Protocol Table 13.4  

•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

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

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

Calculating Direct Emissions from Stationary Combustion

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.

Example: Stationary Combustion Emissions

Stationary Combustion• Natural Gas used for space heating

• 788,400 MMBtu of natural gas used in one year

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.

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

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

Water Utility Emission Sources

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

Data Management

Granularity of Data

Equipment Level DataBest Data if availableDecreases the number of assumptionsAllows for better understanding of opportunities

Grouped Sources within the same categoryExamples are Emergency generators, gasoline trucksData is often maintained at the facility level but sometimes at the corporate level

Bulk DataExamples are total fuel purchased by fuel type or total electricity purchasedGrosser Assumptions will have to be made

IN

CR

EA

SIN

G

GR

AN

ULA

RIT

Y

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

Data Security

User Identification and Password

Departmental accessibility via the Intranet

Access/Write Protection to ensure data cannot be accidentally modified

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

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

Quality Assurance

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?

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

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

Roles and Responsibilities

Support of top-level organizational management

Inventory Manager

Listing of Entity Staff Consulted

Employee Training

GHG Training Program ElementsAudience

Inventory ManagersUtility LeadershipGeneral PersonnelOthers

Comprehensive Curriculums Tailored to Roles Inventory Managers - Inventory Development 101Utility Leadership - GHG management issuesGeneral Personnel - Awareness training

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

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