Encyclopedia of Environmental Science and Engineering, Volume I and II

ENERGY SOURCES—ALTERNATIVES 301

remains or will be again accepted by political authorities and

population, proceed nearer to the demand centers. This could

be of double advantage, should the district heating technol-

ogy be extended, what is recommendable. Whatever kind of

energy source may be used, and in this connection the energy

sources—alternatives are not excluded, the psychological

distance to the energy in general will be shorter at the end

of this century, and this fact may contribute to resolve some

technical and economic problems, and regarding heat it could

be advantageous to reduce urban air pollution.

Employment and Safety

The direct employment of labor in the various energy indus-

tries is a small fraction of the total labor force, however, such

statistics do not reflect the vital need for energy in manufac-

turing and industrial processes and to provide comfort, light,

and labor-saving functions in all working activities. The

employment of labor in some energy industries is listed in

Table 4 along with the injury rate in each industry. Additional

data on the fatal injury rate and the number of injuries, both

fatal and nonfatal, are given for mining activities. Statistics

on injuries in federal government service, excluding mili-

tary personnel, are also given for comparison purposes. It is

apparent that the underground coal mining activity has the

poorest safety record of the energy industries listed, the most

significant problems involving collapse of mine tunnels and

explosions due to the methane released from the coal bed

during mining operations. Research and development is in

progress in the coal mine safety area, including the study of

methods of stabilizing mine tunnels as the coal is extracted

and other methods of protecting the workers in the event of

a fire or mine failure. An example of one novel scheme to

guard against fire in high-methane mines is the provision

of an oxygen-free atmosphere in the mine with the workers

using portable breathing apparatus.^9

Air Pollutants

A survey^10 performed by the National Air Pollution Control

Administration (NAPCA) of the emission of air pollutants in

the United States for the year 1968 identifies energy conver-

sion operations in stationary and mobile power plants as the

major source of carbon monoxide, particulates sulfur diox-

ide, hydrocarbons, and oxides of nitrogen. The total emis-

sions of these pollutants are indicated by source in Table 5.

The Office of Air Programs in the Environmental Protection

Agency (EPA), formerly the NAPCA, has also published a

compilation of air pollutant emission factors^11 which give

the average quantity of pollutants released in the operation

of various fuel-energy conversion system combinations. The

emissions are given for uncontrolled sources unless other-

wise noted. Control measures that may be used to reduce

these emission factors involve treatment of fuels, modifica-

tion of the energy conversion system, or treatment of efflu-

ents depending upon the particular case.

Carbon Monoxide

This poisonous gas is produced by the incomplete com-

bustion of carbon in fuels. When combustion conditions are

well controlled and excess air can be provided, combustion

is generally complete and CO 2 is produced with only trace

amounts of CO. In mobile power plants, such as internal-

combustion engines which account for almost two-thirds of

the total emissions of this pollutant, operating conditions are

quite variable and CO may be in equilibrium in high concen-

trations with other combustion products at the high tempera-

tures involved. These hot gases are cooled rapidly and there

is not sufficient time to convert the CO to CO 2 before they are

expelled from the cylinder.

Emission factors for CO from uncontrolled sources at

average operating conditions are given in Table 6. Control of

these emissions is accomplished, when possible, by proper

TABLE 4

Employment and safety record in selected energy industries

Industry No. of employees, 1969 No. of injuries, 1968

Injury rate per 10^6

man-hours, 1968

(thousands) fatal non-fatal fatal non-fatal

Coal mining 136 311 9460 1.33 40.36

Petroleum and natural gas extraction 282 102 9069 0.10 9.19

Petroleum refining 146 — — — 8.6c

Electric, gas, and sanitary services 664 — — — 6.2c

Automotive service stations 575 a — — — 14.5c

Fuel dealers 101 a ————

Federal government servicesb 3006 — — — 6.9c

a 1967 data.

b Excluding military.

c Includes fatal injuries.

Source: Statistical Abstracts of the US, 1970.

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