Commercial deep-sea mining by China of polymetallic nodules that contain copper, nickel and cobalt among other key minerals, can begin as early as 2030, according to the former head of the State Oceanic Administration.

"With the improvement in deep-sea technology, metal resources under the ocean can be explored and mined within 20 years," said Sun Zhihui.

Last year, China was among the first group of countries approved by the International Seabed Authority to look for polymetallic sulphide deposits, a recently discovered mineral source, in the Southwest Indian Ridge, a tectonic plate boundary on the bed of the Indian Ocean, he said, adding the country is applying to explore for cobalt in a new area in the Pacific Ocean. 

Sun said many countries are developing technologies for commercial mining, but a low-cost method of mining polymetallic nodules has not been found yet.

China has explored more than 80,000 square kilometers of the floor of the Pacific and Indian oceans, Sun said.

Xiang Jianhai, researcher at the Institute of Oceanology under the Chinese Academy of Sciences, said: "When we can carry out commercial mining depends on technological development, financial support and the price of key minerals on the market."

Xiang added that current exploration, such as that carried out by China's manned deep-sea vessel Jiaolong, will provide the technology and geological information for future mining.

He added the extent of the country's deep-sea exploration was catching up with that of advanced countries. Scientists estimate that about 480 million to 13.5 billion tons of polymetallic nodules can be commercially mined, Science and Technology Daily reported.

Polymetallic nodules are rock concretions, mostly about the size of a potato, on the seabed containing metals such as cobalt, manganese, iron, nickel and aluminum, which have huge economic potential.

Xiang said the deep-sea environment was much more difficult to mine compared with land, because mining equipment has to endure high underwater pressures and marine corrosion.

Feng Xisheng, deputy director of underwater robot research at the Chinese Academy of Sciences, said the Jiaolong has dived to 6,000 meters. According to China Ocean News, the nation will conduct a 7,000-meter test dive later this year.

For Jin Jiancai, secretary-general of the China Ocean Mineral Resources Research and Development Association, another obstacle to commercially mining polymetallic nodules is its effect on the deep-sea environment and ecosystem.

Nodule regrowth can take millions of years and that would make such mining unsustainable.

People have little knowledge of most deep-sea species and environments, making environmental assessment almost impossible, Jin told Science and Technology Daily. He added that a law on deep-sea environment protection should be established to avoid potential harm during exploration and mining.

Improving the legal system relating to deep-sea mining and exploration was the key work of the State Oceanic Administration, Liu Cigui, administration director, said at the administration's annual conference in December.

An official of the administration, who did not wish to be named, told China Daily that regulation of deep-sea resources exploration and mining is under discussion, with an aim to protect the ocean.

The total output value of China's marine-based industries was 3.2 trillion yuan ($508 billion) in 2009, accounting for 9.5 percent of the country's GDP, according to the administration's website.