Mobile Combustion CO2 Emissions
CO2 emissions, which account for the majority of emissions from mobile sources, are directly related to the quantity of fuel combusted (e.g. gasoline, diesel, and CNG) and thus can be calculated using fuel consumption data.
The LGOP provides four methodologies for calculating mobile combustion CO2 emissions:
Recommended Approach: Known Fuel Use
- Identify total annual fuel consumption by fuel type. This can be obtained from accounts payable, departmental records, fleet manager, fuel tracking system, maintenance records, fuel vendors/suppliers, etc.
- Determine the appropriate emission factor using Table G.9 in Appendix G of LGO Protocol
- Calculate total CO2 emissions using Equation 7.2.
Alternate Approach 1: Detailed Annual Mileage and Fuel Efficiency
- Identify the vehicle make, model, fuel type, and model years for all the vehicles operated by local government.
- Identify the annual distance traveled by vehicle type. Sources include odometer readings, maintenance records, or trip manifests that include distances to destinations. Alternatively, reimbursement records can be used using Equation 7.3.
- Determine the fuel economy of each vehicle (U.S. EPA’s website www.fueleconomy.gov).
- Convert annual mileage to fuel consumption. If there is accurate information about the driving patterns of the local government fleet, apply a specific mix of city and highway driving, using Equation 7.4. Otherwise, assume 45 percent of vehicles’ mileage is highway driving and 55 percent is city driving.
- Calculate total CO2 emissions using Equation 7.2 in the Recommended Approach section.
Alternate Approach 2: Fuel Estimates Based on Dollars Spent
- Identify total annual dollars spent by fuel type. Sources include collected fuel receipts and purchase records for fuel station accounts.
- Identify the cost per gallon for each fuel type. If cost is not available, go to the Energy Information Administration at http://tonto.eia.doe.gov/oog/info/gdu/gasdiesel.asp.
- Convert annual dollars spent to fuel consumption for each fuel type.
- Calculate total CO2 emissions using Equation 7.2 in the Recommended Approach section.
Alternate Approach 3: Proxy Year Fuel Use Data
Typically, this approach is used in cases of one or a few vehicles. Generally, it should not be used for a large group of vehicles or for the entire vehicle fleet.
- Identify total annual fuel consumption by fuel type in proxy year (calendar or else fiscal year).
- Adjust the fuel consumption by fuel type based on any changes in fleet size and composition between the proxy year and the inventory year.
- Calculate total CO2 emissions using Equation 7.2 in the Recommended Approach section.
