Encyclopedia of Environmental Science and Engineering, Volume I and II

1.58 
 10 12 tons of coal in the US in seams at least 14 inches

thick and at depths of less than 3000 feet, and about half of

this is considered recoverable at a cost near current levels.

These deposits are described by grade and sulfur content in

Table 12. On the same basis, the world’s coal resources are

8.3 
 10 12 tons. The time of peak annual recovery and the

time at which about 90% of this resource will be consumed

are projected to be the year 2150 and 2440, respectively, for

the US and 2150 and 2380 for the world. The annual extrac-

tion of bituminous coal in the world was in 1974 2245 M of

tons, the extraction of lignite 847 M of tons (Data source:

Friedensburg/Dorstewitz, Enzyklopaedie Naturwissenschaft

und Technik, Muenchen, 1980).

Sulfur is present in coal as pyrite (FeS 2 ) and organic

sulfur in roughly equal amounts. The organic sulfur is dif-

ficult to remove, while only 30% of the sulfur present as

pyrite is removed by the standard coal-cleaning technique

of crushing and flotation. Processes are available for the

liquefaction and gasification of coal and lignite, the pro-

cess for the liquefaction and gasification of coal had worked

before the petroleum era and is working with improved

technologies in semi-industrial installations, the process for

the liquefaction and gasification of lignite may go in the

near future into the phase of pilot plants. These processes

will provide a sulfur-free fuel in more convenient form.

Hydrogenation plants are foreseen that will produce 100,000

bbl/day of synthetic crude oil from 3.24 
 10 5 tons of coal^34

at a cost after sufficient development of about the double of

the world marked price of natural crude oil, that means, all

gasification and liquefaction plants are not yet competitive

with the conventional process of refining natural crude oil.

But the engagement of several industrial countries demon-

strates that the technical processes of substitution exist and

are available for a certain period to overcome the problems

of modification of the world energy economy until alterna-

tive energy sources of long-term significance and necessary

quantities are available for the then modified applications in

the human life.

The liquid of synthetic crude oil has a high gasoline

content and the process yields a high-sulfur char residue.

In the gasification of coal, the sulfur is recovered as H 2 S.

Carbonization, or pyrolysis, yields a gas, mostly hydrogen,

FIGURE 4 Portion of central station electric cost attributable to the transportation of energy.

Natural gas by pipeline

Coal by integral train

Oil by pipeline

Oil by tankship

550 kv, ac

(Source: Reference 29.)

Electric transmission

345 kv, ac

220 kv, ac

Distance (miles)

100 200 300 400 500 600 700 800

0

0.5

1.0

1.5

2.0

2.5

3.0

Cost (mils/kwh of electricity produced at

conversion efficiency of 33%)

308 ENERGY SOURCES—ALTERNATIVES

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