Quezon City, Philippines — Filipinos have become used to talk about "dendrothermal energy." The fancy name means primarily wood-fired, thermal power plants. The Ministry of Energy's 10-year energy program for 1980-89 envisages the construction of close to 200 megawatts of wood-fired plants annually from 1981 to 1984. In 1984, the plan predicts, these plants will provide the equivalent of 1.9 million barrels of oil, and by 1989, 3.4 million barrels.
The basis of such plans is a remarkable tree, called ipil-ipil by the Filipinos, Leucaena luecocephala by scientists. It grows so fast that in three or four years it will stand 25 to 30 feet tall and have a diameter of about five inches. It can then be harvested, dried, and burned. New growth springs from the stump, and another harvest is ready in perhaps three years. Moreover, the leaves contain a high amount of protein and can be used as animal feed. And the ground is enriched with nitrogen.
The National Electrification Administration has been put in charge of this program. The administrator, Brig. Gen. Pedro G. Dumol, says that three ipil-ipil plantations have already been started. By the end of the year, some 12,000 hectares (30,000 acres) of trees will have been planted, he reckons.
The first 3-MW plant should be completed by the end of 1981 or early in 1982.
The plan calls for 1,000-hectare tree plantations (1 hectare equals about 2.5 acres) planted over three or four years in 10 modules of 100 hectares each. These should provide a continuous yield of wood for a 3-MW plant.
Each hectare should yield 20 to 50 tons of wood per year. After felling, the ipil-ipil logs lose about 30 percent of their weight in three months. Then they will be chipped and preheated before being fed into the power plant's boilers to make steam. The plant will consume about 100 tons per day.
Each plantation, as General Dumol plans it, will be run by about 10 farm families combined in an association. They will become 30 percent owners of the stock of a power plant corporation. The local electrical cooperative will own 50 percent and the National Electrification Administration, 20 percent.
Each 3-MW plant is expected to cost about $4.5 million. That includes transmission lines and roads.
The farmers will often be "slash and burn" operators. Traditionally, they have cut down a small area of forest, burned it so the ash fertilized the ground , and then farmed it until the soil was no longer fertile. Then they move, repeating the process.
General Dumol figures these farmers will make more money from raising ipil-ipil trees than from their slash-and-burn agriculture. Since the first planting will need about 10,000 young trees per hectare, it will require much work. But the farmers can also plant corn in the one-meter space between the rows of newly planted trees and after a tree harvest.
Noting that the corn stalks help fertilize the trees later, General Dumol said the two "grow quite well together."
Many of the ipil-ipil plantations will be on hills denuded of their forests. The ipil-ipil trunks are small enough to be handled by men without machinery. General Dumol talks also of setting up a simple cable system so the trees can be hauled down from the hillsides by gravity. He believes that some power can perhaps be created in the process of braking the speed of their fall.
The power from the woof-fired thermal plants promises to be considerably cheaper than that created with bunker oil. The plantations would provide useful jobs. Further, they would slow the shrinkage of Philippine forests. These covered about 18 million hectares of forest in 1960 and only 10 million in 1978.
There are problems, however. The ipil-ipil trees tend to take phosphorus from the soil. Moreover, since dense stands of ipil-ipil inhibit growth of the understory vegetation such as grasses, there is some danger of surface erosion on steep slopes. These stands can also suffer infestations of beetles.
Whatever, national planners see dendrothermal energy as making a substantial contribution to the nation's energy needs. Already some 45 plantation sites have been located.
The planners are also counting on mini- hydro projects as an important source of power. The Philippine islands are mostly mountainous. Rainfall, though varying widely, averages around 120 inches a year. So there are many small rivers or streams, as well as some large rivers, that can be harnessed for power generation.