Environmental Engineering Reference
In-Depth Information
LNG trade. The largest importers of piped gas are
the United States, from Canadian fields in Alberta and
British Columbia; Germany, from Siberian Russia, the
Netherlands, and Norway; and Italy, mostly from Algeria
and Russia. Japan buys more than half the world's LNG,
mainly from Indonesia and Malaysia. Other major
LNG importers are the South Korea and Taiwan, both
from Indonesia and Malaysia; and France and Spain,
from Algeria.
Most of the techniques underpinning these far-
flung, complex systems have either ceased growing
or are increasing at much slower rates than they did
until the 1970s. As a result, we may never see a larger
overburden-removing shovel, refinery, or supertanker.
The reasons for this end of growth are not primarily
technical but rather environmental, economic, and social
(see chapters 11 and 12). Concentration of fuel extrac-
tion and processing and electricity generation in progres-
sively larger facilities has further increased the inherently
high power densities of fossil-fuel-based energetics. Most
of the world's fuel extraction goes on with densities
surpassing l kW/m
2
, and fuel-processing facilities have
similarly high throughput densities. But the overall
power densities of production systems are considerably
lowered by the extensive transportation and transmis-
sion networks needed to deliver fuels and electricity
as well as by the requirements of pollution and heat con-
trol. Some power production densities may be well below
50 W/m
2
.
tricity generation), from universally adopted large-scale
conversions (hydroelectric generation) to promising but
still marginal techniques (photovoltaics), and from sys-
tems that could conceivably displace fossil fuels (nuclear
fission) to options that will always remain restricted (geo-
thermal electricity generation). Although biomass is by
far the most important source of nonfossil energy, it is
impossible to offer an accurate account of its consump-
tion because most of these fuels are gathered directly by
more than 500 million poor world families rather than
being traded.
Uncertain conversion factors used to express these uses
in common energy units introduce additional errors, and
hence it is not surprising that plausible estimates of the
global use of biomass energies differ by more than 10%.
FAO (1999) estimated that about 63% of 4.4 Gm
3
of
harvested wood were burned as fuel during the late
1990s. With about 0.65 t/m
3
and 15 GJ/t of air-dried
wood, this would be an equivalent of about 27 EJ. In
some countries a major part, and even more than half,
of all woody matter for household consumption is gath-
ered outside forests and groves from bushes, tree planta-
tions (rubber, coconut), and roadside and backyard trees.
Rural surveys show that nonforest fuel wood accounted
for more than 80% of wood burned in Bangladesh, Paki-
stan, and Sri Lanka (RWEDP 1997). A conservative esti-
mate of this nonforest woody biomass could raise the
total to anywhere between 30 EJ and 35 EJ.
Crop residues produced annually in poor countries
added up to about 2.2 Gt of dry matter during the late
1990s (Smil 1999a). Burning in the field, recycling, and
feeding to animals account for most of their disposal, and
if about 25% of all crop wastes (mostly cereal straws)
were used by rural households, this would add about 8
EJ. Collected dried dung amounts to less than 1 EJ. A
9.2 Nonfossil Contributions: Biomass and Primary
Electricity
Nonfossil contributions range from critical but inefficient
and environmentally ruinous inputs (fuel wood and crop
residues in the poor world) to mere curiosities (tidal elec-
