But government support is key, said Richard Gledhill, global leader of Climate Change & Carbon Market Services in London for PricewaterhouseCoopers, a consultancy that helped head the research.
According to the U.S. International Energy Agency, holding climate change to just a 2 degrees Celsius increase over the next two decades will require $9 trillion in extra spending, he said.
"The private sector has a key role to play in delivering the required investment at the scale required to avoid dangerous climate change. But it will only do this if there is a clear, long-term policy framework to underpin prospects of a reasonable return," Gledhill said.
The project defined greentech as technologies, products and services that benefit users as much or more than conventional alternatives, while limiting the impact on the natural environment and promoting efficient and sustainable use of energy, water and other resources.
While such changes are needed worldwide, China's rapid growth and dizzyingly fast urbanization are contributing to a building boom that has created more than twice the floor space as in the U.S.
About 18 million people migrate from rural areas to the cities each year, so that by about 2050 China will have more than 200 cities with populations of more than 1 million people, the report said.
Such growth will require huge increases in use of energy, water and materials that will force China to adopt new, environmentally friendly technologies, it said.
Both Chinese and foreign companies will find new opportunities, though they still face challenges, particularly in overcoming barriers to transfer of technologies and preventing piracy of intellectual property such as patents.
Such issues were a focus of a conference on green technology this week in Shanghai, sponsored by the American Chamber of Commerce in Shanghai and other groups and companies involved in the China Greentech Initiative.
Many of those attending urged China and the United States to make real progress in pushing ahead with collaboration on clean energy projects as President Barack Obama prepares to visit Beijing in November.
Breakthroughs are urgently needed if a U.N. meeting in Copenhagen, Denmark, this December is to succeed in striking a pact to succeed the Kyoto Protocol, which bound 37 industrial countries to reduce greenhouse gas emissions.
Apart from government support for technologies that might not pay for themselves fast enough to entice private investors, China can help by easing controls on its financial sector and private equity to help bring in the funds needed for clean energy projects, said Stan Barer, co-chairman of the U.S.-China Joint Clean Energy forum.
"Is there a market here and can I make money in it, and can I get finance?" Barer told the conference. "Finance wants proof it will make money," he said.