Greenpeace activists try to prevent the unloading of coal at the BLCP power plant in Rayong yesterday.

The 20 protesters - seven foreigners and 13 Thais - tried to immobilise cranes that would have been used to unload the coal from an Australian ship. However, police at Map Ta Phut Industrial Estate arrested the activists before they reached the cranes in a rubber dinghy and a long-tail boat.

The activists only succeeded in hanging a banner saying "Clean Energy Now" at BLCP's harbour.

"The BLCP coal plant will exacerbate the impact of climate change, which is already starting to exact a heavy toll on the people and economies of Thailand and Southeast Asia," said Tara Buakamsri of Greenpeace Southeast Asia.

"It does not help that Australia is fuelling climate change in the region with its coal exports. Thailand must stop any further use of coal and put a policy in place for the massive increase of renewable energy and energy-efficiency projects."

Greenpeace claimed the plant would release nearly 12 million metric tonnes of carbon dioxide annually - and cause Thailand's carbon emissions to rise by almost 6 per cent a year.

Coal is the dirtiest of fossil fuels, emitting 29 per cent more carbon per unit of energy than oil and 80 per cent more than gas. It is a major contributor to climate change, Greenpeace says.

A senior BLCP staff member denied the accusation, saying the plant had implemented all measures demanded by its environmental impact assessment.

Speaking on condition of anonymity, the source claimed the plant used high-grade bituminous coal - not low-grade lignite that would emit a high volume of sulphur dioxide and carbon dioxide to the atmosphere.

The source said the protest did not cost any economic damage to the company and the unloading of the coal would go ahead as scheduled.

"This was the third time the activists have visited us in this way. We are not surprised anymore and are well prepared to cope with it," the source said.

The plant, jointly owned by Thailand's Banpu Plc and Hong Kong-based China Light and Power Corp, is an independent power producer with the capacity to generate 1,434 megawatts of electricity.

BLCP has a contract to sell electricity to the Electricity Generating Authority of Thailand (Egat) for 25 years.

The plant is currently being tested, with its first transmission to Egat due next month.