China plans to collect new samples of combustible ice - a kind of natural gas hydrate - from the northern part of the South China Sea next year, a senior official said.

The move is seen as an effort to ease the country's dependence on oil and coal.

Combustible ice usually exists on the seabed or in tundra areas. It is formed by natural gas and water in conditions of high pressure and low temperatures. It can be lit up like solid ethanol, which is why it has the name "combustible ice".

As a kind of clean energy, combustible ice is regarded as a potential alternative to coal and oil.

The country's first deep-sea exploration vessel for the reconnaissance of combustible ice, which was coded Ocean No 6, has been put into the sea to carry out the combustible ice survey in the South China Sea, according to the Guangzhou Marine Geological Survey Bureau of the Ministry of Land and Resources.

The vessel was independently developed by China, and cost 400 million yuan ($63 million) to build, official figures showed.

The vessel has a gross tonnage of 4,600 tons and an endurance of 15,000 nautical miles. It has been equipped with underwater remote-control survey facilities and other high-tech devices.

China announced its first discovery of the resource on the bed of the South China Sea in May 2007 after nine years of research.

The reserves of combustible ice are ex-pected to reach 19.4 billion cubic meters in the Shenhu sea area in the northern part of the South China Sea, said Yang Shengxiong, chief engineer of the Guangzhou Marine Geological Survey Bu-reau of the Ministry of Land and Resources.

It has been estimated that the total volume of organic carbon in the world's combustible ice is twice the combined volume of the world's proven coal, oil and natural gas re-serves.