In its first major report on bioenergy, the U.N. tried to temper the enthusiasm over biofuels by raising the alarm about their potential negative impact. The report was issued just days after a climate conference in Bangkok said the world had both the money and technology to prevent the sharp rise in global temperatures blamed in part on greenhouse gas emissions.
Biofuels, which are made from corn, palm oil, sugar cane and other agricultural products, have been seen by many as a cleaner and cheaper way to meet the world's soaring energy needs than with greenhouse-gas emitting fossil fuels.
European leaders have decided that at least 10 percent of fuels will come from biofuels, like ethanol, by 2020, and the U.S. Congress is working on a proposal that would increase production of biofuels by seven times by 2022. With oil prices at record highs, biofuels have become an attractive alternative energy source for poor countries, some of which spend six times as much money importing oil than on health care.
But environmentalists have warned that the biofuel craze can do as much or more damage to the environment as dirty fossil fuels, a concern reflected throughout the report, which was released Tuesday in New York by U.N.-Energy, a consortium of 20 U.N. agencies and programs.
U.N.-Energy chairman Mats Karlsson said it only seemed natural to look to biofuels for energy since a quarter of the world's population has no access to power.
"What would be more interesting than to reflect on a source of energy that takes simply sunshine and water, and transforms it into power through photosynthesis?" he told a press conference in New York. "Well, when you reflect on it you find that there are many challenges."
The report said bioenergy represents an "extraordinary opportunity" to reduce greenhouse gas emissions. But it warned that "rapid growth in liquid biofuel production will make substantial demands on the world's land and water resources at a time when demand for both food and forest products is also rising rapidly."
Changes in the carbon content of soils and carbon stocks in forests and peat lands might offset some or all of the benefits of the greenhouse gas reductions, it said.
"Use of large-scale monocropping could lead to significant biodiversity loss, soil erosion and nutrient leaching," it said, adding that investments in bioenergy must be managed carefully, at national, regional and local levels to avoid new environmental and social problems "some of which could have irreversible consequences."
It noted that soaring palm oil demand has already led to the clearing of tropical forests in southeast Asia. Such clearings could result in emissions that were even higher than those caused by fossil fuels.
In addition, the diversion of land used to grow food for fuel will increase food prices for basic commodities, putting a strain on the poor. Already, there has been recent steep rises in maize and sugar prices, the report said.