NATURAL GAS FOR CARS AND TRUCKS: OPTIONS AND CHALLENGES - Natural Gas-powered Cars and Trucks: Options and Issues - page 4

Source: U.S. Department of Energy, Energy Information Administration, Natural Gas
Gross Withdrawals and Production, http://www.eia.gov/dnav/ng/ng_prod_sum_
dcu_NUS_m.htm.
Figure 1. U.S. Natural Gas Production. (2000-2013)
Among the key factors determining the attractiveness of natural gas as a
transportation fuel is its price relative to diesel fuel. The energy content of a
given volume of natural gas in compressed or liquefied form differs from that
of refined petroleum products. For example, one gallon of LNG has 82,644
British thermal units (Btu) of energy compared to 139,000 Btu per gallon of
diesel fuel and 114,000 Btu per gallon of gasoline. 4 Prices can be compared by
converting natural gas to its gasoline gallon equivalent (GGE) or diesel gallon
equivalent (DGE). Measured by Btus, a barrel of oil has historically cost
several times as much as a comparable unit of natural gas ( Figure 2). U.S.
natural gas prices fell by half between 2008 and 2014 as increasing supplies
from shale formations became available. The competitive price advantage that
natural gas now demonstrates could be eroded if crude oil prices fall or natural
gas prices rise.
V EHICLE T ECHNOLOGIES U SING N ATURAL G AS
Several different technologies can be used to harness natural gas as a
vehicle fuel. Some of them require pressurized systems to burn the fuel in a
gaseous state, and others convert natural gas to a liquid. Still others process
natural gas into a variety of liquid fuels suitable for powering internal-
combustion engines.