Environmental Engineering Reference
In-Depth Information
data for 2001 show a total annual throughput of about
725 Mt (30.5 EJ) of crude oil and primary energy con-
sumption of roughly 3.5 EJ, or 4.6 GJ/t of crude oil, an
equivalent of about 11% of energy in the input (Worrell
and Galitsky 2003). Process rates for gasoline (most of
it produced by catalytic cracking) is just over 6 GJ/t
(Brown, Hamel, and Hedman 1996), implying EROI of
about 7.3. Similarly, Cleveland (2005) put the EROI
range for U.S. gasoline at 6-10. Energy use in refining,
amounting to 4%-11% of crude oil input, or 1.7-4.6
GJ/t, lowers the fraction of initial energy delivered in
refined products to as little as 0.8 and as high as 0.93;
values of 0.85-0.88 (EROI 6.7-8.3) may be typical for
most refined products.
U.S. data show that natural gas exploration claims en-
ergy equal to about 0.6% of the discovered fuel. This is
followed by a sequence of field and transportation losses
that appreciably reduce the fuel's marketable share, and
whose totals are available in considerable detail in annual
statistics (EIA 2005d). In 2005 flaring amounted to
about 4% of global natural gas production, with extremes
ranging from an equivalent of nearly 90% of annual out-
put in Nigeria to less than 0.5% in the United States
(Mouton 2005). U.S. extraction losses equal or surpass
all flaring and venting (about 3.5% of total production
in 2003). Lease fuel, used in well and field operations,
claims about 3%, and in old gas fields repressurization is
the main energy debit before the gas gets processed and
distributed; in 2003 it claimed nearly 15% of dry gas
extraction.
Specific energy embodied in natural gas pipelines
(seamless pipes for smaller diameters and welded sheet
steel for pipelines with diameters of 50 cm and larger)
varies with their function (trunk lines, gathering and dis-
tribution lines) and diameter, but it always prorates to a
very small share of the energy transported by the pipeline
over its lifetime of at least 30 years. U.S. natural gas
transmission pipelines embody on average materials
worth about 1.1 TJ/km, construction 1.3 TJ/km, and
engineering and maintenance 1.2 TJ/km (Meier 2002).
These energies represent less than 0.1% of energy in the
fuel transmitted through a pipeline during its lifetime.
Centrifugal compressors that pressurize the transported
gas to 1.4-10.3 MPa in stations spaced at 60-160-km
intervals have been traditionally powered by natural gas,
but electric motors have been making some inroads.
Shares of natural gas consumed by pipeline distribution
depend on the total length of a network; in Canada and
the United States they are above 3%.
Leakage from U.S. natural gas pipelines averages
1.5%G0.5% of the transported fuel (Lelieveld et al.
2005). In contrast, Reshetnikov, Paramonova, and
Shashkov (2000) found that during the early 1990s the
long and aging gas pipelines in the states of the former
USSR were very leaky, losing annually 47-67 Gm
3
,or
6%-9% of the transported total (a loss larger than the an-
nual natural gas consumption in Saudi Arabia and equal
to annual imports to Italy). But this conclusion is not
supported by Lelieveld et al. (2005), who found that the
leakage from Russian pipelines, at 1%-2.5% of the trans-
ported fuel, is comparable to the U.S. losses. With all
of these production and transportation uses and losses,
shares of natural gas delivered to consumers may thus
amount to more than 90% (EROI
>
12) or less than
70% (EROI
<
3.3) of the initially extracted fuel, with typ-
ical shares between 0.80 and 0.90 (EROI 5-10).
LNG projects require considerable investments in the
liquefaction plant, a fleet of carriers and regasification
and storage facilities. The total for a 5-Mt LNG/year
plant was $3-4 billion in the early 2000s (Total 2005).
