The world will have to triple coal consumption between now and 2000 if any kind of real economic growth is to be sustained, according to a major energy study released yesterday.

Describing itself as "carefully optimistic," the World Coal Study organization of researchers from 16 countries concluded that enough coal is available and that it "can be mined, moved and used at the most stringent environmental protection standards and at acceptable costs" to accomplish the task.

The only hitch is that key decisions must be made now, before heavy demand begins, because of the time involved in setting up mines, rail lines and shipping facilities, the study said.

The two-volume report, entitled "Coal: Bridge to the Future," was coordinated by Dr. Carroll L. Wilson of the Massachusetts Institute of Technology and involved 38 high government and international corporation leaders.

Wilson directed a 1977 workshop on alternative energy strategies study that predicted recession would accompany reduced Middle East oil output in the early 1980s. "We were too optimistic," he said in an interview. "It's happening now, and at lower oil levels than we predicted."

The new report, Wilson said, shows there is a way out.

It involves major conservation efforts, marshaling of all other available energy resources and a 10- to 15-fold increase in world coal trade."Without such a coal expansion the outlook is bleak," he said.

To maintain a modest 3 percent annual average growth rate worldwide, world oil exports would have to rise about 4 million barrels per day from the current 26-million-barrel level, the report estimated. Instead, exports are likely to drop to 22 million barrels per day because of growing internal demand or conservation policies in exporting countries.

Tar sands and heavy oil shales offer promise after 2000 but not before; natural gas will require building expensive, time-consuming facilities, and nuclear power is suffering from "political uncertainty" that is delaying new plant construction worldwide, the report said.

Conservation "may well become one of the world's largest energy 'sources'" over the next 20 years but cannot do the job alone, the study continued. Hydropower, alcohol fuels and solar energy along with other "alternative" energy sources will make a growing contribution, it said, but only really come into their own after 2000.

Until then the world must rely on coal, the study concluded.

In fact, where oil supplied two-thirds of the power for economic growth in developed countries during the last 20 years, coal can and should supply that much over the next 20, it said, with oil providing little or none of the economic growth.

This would require a total world increase in coal consumption from 2.5 billion metric tons this year to 6 billion or 7 billion tons by 2000, an annual growth rate of 4 to 4.5 percent, about the same rate as coal use grew during the 1950s, the study said. Reserves are ample, so vast they are "difficult to comprehend," totaling about 250 times the world 1977 production.

But it will take money, about $200 billion over the coming two decades for mining, transport, ports and ships, the study said, and $740 billion for construction and conversion of power plants. Government help will clearly be essential, not only in providing capital but also in smoothing licensing procedures, providing a stable investment climate and setting up believable environmental standards.

The researchers acknowledged that coal's environmental impact is one of its most controversial aspects. However, they said, crude oil at $35 a barrel means that coal can cost up to $165 per metric ton and still be cheaper. Right now, the study said, all environmental requirements on mining, reclamation, emissions and wastes can be met at an average of $35 a ton in Japan, for example, where controls are strict, and the total cost per ton is $80.

"It is likely that environmental concerns or control costs will preclude the development of certain sites or certain coal resources," the study said. "However, there are so many possible sites and resources remaining worldwide that such exclusions will not be a limiting factor to the expansion of coal use."

The only environmental impact of coal about which nothing can be done is a worldwide buildup of carbon dioxide in the atmosphere. Researchers fear this could lead to a "greenhouse effect" that would warm the atmosphere, change the earth's climate patterns and disrupt the growing seasons.

The study acknowledged that coal puts out 25 percent more carbon dioxide than oil, but added, "most [researchers] expect that there are at least several decades to evaluate the carbon dioxide modification issue."