Introduction - Mathematics and Statistics for the Environment - page 29

STANDARD CONVERSIONS FOR MANUAL CALCULATIONS

Volume Weight Length

1 gal = 3.78 L 1 lb = 453 g or 0.453 kg 1 in. = 2.54 cm

1 L = 0.26 gal 1 kg = 2.2 lb 1 cm = 0.39 in.

1 tsp = 5 mL 3.28 ft = 1 m

1.7 GREENHOUSE GAS EMISSION NUMBERS TO EQUIVALENT UNITS
This section describes the calculations used to convert greenhouse gas emission numbers—an area
of increasing concern for environmental practitioners—into different types of equivalent units.

1.7.1 e leCtriCity r eduCtions (K iloWatt -h ours )
The U.S. Environmental Protection Agency's Greenhouse Gas Equivalencies Calculator uses the
Emissions & Generation Resource Integrated Database (eGRID) of U.S. annual non-baseload
CO 2 output emission rates to convert reductions of kilowatt-hours into avoided units of car-
bon dioxide emissions. Most users of the Equivalencies Calculator who seek equivalencies for
electricity-related emissions want to know equivalencies for emissions reductions due to energy
efficiency or renewable entry programs. These programs are not generally assumed to affect base-
load emissions (the emissions from power plants that run all the time), but rather non-baseload
generation (power plants that are brought online as necessary to meet demand). For that reason,
the Equivalencies Calculator uses a non-baseload emissions rate (USEPA 2012a).

1.7.1.1 Emission Factor

7.0555 × 10 -4 metric tons CO 2 /kWh

Note: This calculation does not include any greenhouse gases other than CO 2 , and it does not
include line losses.

1.7.2 p assenger v ehiCles per y ear
Passenger vehicles are defined as two-axle, four-tire vehicles, including passenger cars, vans,
pickup trucks, and sport/utility vehicles. In 2010, the weighted average combined fuel economy
of cars and light trucks was 21.6 miles per gallon (FHWA, 2012). The average vehicle miles trav-
eled in 2010 was 11,489 miles per year. In 2010, the ratio of carbon dioxide emissions to total
greenhouse gas emissions (including carbon dioxide, methane, and nitrous oxide, all expressed
as carbon dioxide equivalents) for passenger vehicles was 0.985 (USEPA, 2013a). The amount
of carbon dioxide emitted per gallon of motor gasoline burned was 8.92 × 10 -3 metric tons, as
calculated in the Section 1.7.3.
To determine the annual greenhouse gas emissions per passenger vehicle, the following meth-
odology was used: Vehicle miles traveled (VMT) was divided by average gas mileage to deter-
mine gallons of gasoline consumed per vehicle per year. Gallons of gasoline consumed was
multiplied by carbon dioxide per gallon of gasoline to determine carbon dioxide emitted per
vehicle per year. Carbon dioxide emissions were than divided by the ratio of carbon dioxide emis-
sions to total vehicle greenhouse gas emissions to account for vehicle methane and nitrous oxide
emissions.