ISTANBUL — Fatih Birol, executive director of the International Energy Agency (IEA), on Tuesday lauded China's efforts to extract combustible ice from sea.

Referring to the fact that China leads the world in terms of its research and development efforts, Birol said "China takes once again the leadership."

"Today China is number one in terms of the wind, number one in terms of the solar and number one in terms of the energy-efficiency effort as well as in nuclear power," he told Xinhua.

On Sunday, China completed in the South China Sea a 60-day trial of mining gas hydrates, commonly known as combustible ice, marking a breakthrough in the search for alternative clean energy resources.

It was announced that the exploration produced over 300,000 cubic meters of gas, mainly methane, with an average daily extraction of more than 5,000 cubic meters of high-purity gas, and a highest daily output of 35,000 cubic meters.

"What we are seeing is that the natural gas industry is in transformation," Birol said. "We are seeing more and more unconventional gas being part of the total gas mix."

Speaking of the ongoing efforts on methane hydrate by China, Japan and others, as US is doing on shale gas and Australia on coalbed methane, the IEA chief commented "it is not a technology for today but maybe for tomorrow."

China began its research on combustible ice in 1998, as one cubic meter of combustible ice, a kind of natural gas hydrate, equals 164 cubic meters of regular natural gas.