It is possible to produce liquid fuels such as alcohol from plants, thus utilizing the energy being stored currently by photosynthesis. When the competing uses for plants as sources of food, lumber, paper, fiber, and other products are taken into account, there does not appear to be much promise of being able to obtain amounts of energy from this source which are comparable to the industrial power requirements.

GEOTHERMAL ENERGY

Power plants using steam from wells drilled in volcanic areas have been in operation for more than half a century. The first such plant was in­stalled near Larderello in Tuscany, Italy, in 1904. Subsequently, Italian power capacity from geothermal energy has been progressively increased to a present figure of about 400 megawatts.

In the United States, the first geothermal power plant, with a capaci­ty of 12.5 megawatts at The Geysers in northern California, began opera­tion in 1960. By 1969 the power capacity had been increased to 82 mega­watts. In New Zealand geothermal power production was begun in 1958 and has now reached a level of 290 megawatts.

In other parts of the world — Mexico, Japan, Iceland, and the ussr — geothermal plants of small capacity have either recently been installed or are under construction. The total world geothermal power capacity for the early 1970’s is estimated to be about 1,124 megawatts.

From a study of the world’s known geothermal areas, White (1965) estimated roughly that the ultimate amount of geothermal power that may be developed is about 60,000 megawatts. White estimates further that since geothermal plants operate principally by depleting natural reservoirs of stored thermal energy, the life expectancy of geothermal plants is on the order of only about 50 years.