Investment in China's environment protection industry during the next five years is estimated to be 23 trillion yuan ($3.7 trillion), according to Lan Hong, a professor of environmental finance at Renmin University of China.

Funding needed for environmental infrastructure construction would be about 8.6 trillion yuan while that for the renewable and clean energy industry is about 2.3 billion yuan, said Lan at the Tianjin Yujiapu Forum on Wednesday, quoting an ongoing study on green finance she does with colleagues.

The study will be complete in November and reported directly to Premier Li Keqiang, she said.

Fiscal investment in the environment sector during the next five years will be about 2 billion a year, Wu Shunze, deputy head of the Chinese Academy for Environmental Planning, said last month.

"The introduction of foreign capital and technology will be necessary and the newly established free trade zones will play a vital role," said Lan, a specialist in environmental finance with the World Bank between 2007 and 2009.

"At the same time, China has also to learn to better adhere to the international standard in banking and finance concerning environment protection".

The Industrial Development Bank is so far the only Chinese bank to embrace the Equator Principles, the international standard for effective environmental risk management of project investments.

"I believe more Chinese banks will follow suit with more Chinese banks going overseas and the revision of environmental and financial laws," Lan said.

Dai Qing contributed to the story