When one of Silicon Valley’s best-known venture capitalists speaks these days, he has a message that catches most of high-technology audience by surprise. John Doerr, a general partner at one of the preeminent Valley venture firms, Kleiner, Perkins, Caufield & Byers, is evangelizing for green technology, or innovations that can promote sustainable growth on the planet.

Greentech, as Mr. Doerr like to call it, is different from what interests most of the Valley: Internet, web 2.0, software, semiconductors, or mobile and wireless communications. These are still interesting but greentech is where the future lies, says Mr. Doerr.

“This is the mother of all markets,” Mr. Doerr said Friday at the TiE conference, a gathering of South Asian entrepreneurs, held in Santa Clara, California. “There has been no innovation in green technology, things like clean energy and water for the last 30 years. A small change now can make a big difference.”

Entrepreneurs and the technology industry better take notice. Mr. Doerr has a track record that brooks little argument.

Mr. Doerr started in Silicon Valley with Intel in 1974 just as the company invented the 8080 processor. In 1980, he joined Kleiner Perkins and since then has backed some of the biggest technology companies in the IT industry including Google, Sun Microsystems, Intuit, and Amazon.

Once again, he may be on to something. Cleantech investments in North America grew 35 percent to $1.63 billion in 2005, according to industry monitor Cleantech Venture Network. And last year, companies in the solar industry had some of the best returns in the public market (see Solar Energy’s Bright Future).

It may be why Mr. Doerr is unafraid to pronounce greentech as the “biggest economic opportunity of the future.”

Going Green for the Planet

Mr. Doerr has a national ally in former U.S. Vice President Al Gore.

Earlier this month, Mr. Gore delivered a speech to a group of Silicon Valley stalwarts, including Mr. Doerr and Steve Jobs, on the issue of the need for clean energy.

Not surprisingly, at the TiE conference, Mr. Doerr showed some startling slides from Mr. Gore’s recent presentation about the impact of global warming on economic hot spots like the San Francisco Bay Area, and Mumbai, India.

“The U.S. consumes 24 percent of the world’s energy despite having just 4 percent of the world’s population,” said Mr. Doerr. “Now if India and China develop in the same way as the U.S., then we will choke the planet to death.”

Ounce of Prevention

And as a small step to prevent that, Mr. Doerr and Kleiner Perkins are pouring money into startups that offer some hope against this.

“Our planet is warming at about 1 percent a year,” said Mr. Doerr. “We need to reduce the emitted carbon dioxide every year.”

One way to do that is to find better ways to generate power. Which is why Kleiner Perkins, said Mr. Doerr, has put its money in a company that promises to do that.

“We are investing in a startup that can generate electricity with 40 percent fewer carbon emissions,” said Mr. Doerr. However, he declined to reveal more about that startup, saying the company is still in a stealth mode.

Kleiner Perkins is backing Mr. Doerr’s passion. Over the last five years, the VC firm has invested in seven greentech startups. It has also earmarked $100 million from its latest fund for investment in greentech investment, said Mr. Doerr.

Finding green technology alternatives is also important for America’s safety, said Mr. Doerr. “Our addiction to oil has resulted is us financing both sides of the war on terrorism,” he said. “We are fighting the terrorists; at the same time we are paying for the mullahs who encourage the acts.”

Policy and Regulation

Mr. Doerr is not the only VC hunting for deals in greentech. From Peter Wagner, general partner at Accel Partners, to Dick Kramlich at New Enterprise Associates, every other VC is hunting for a startup that promises innovation in this market segment.

“If you have any interesting ideas in nuclear energy deals, then come see us,” hustles Mr. Wagner.

Still there are some VCs who are avoiding investing in clean technology startups as returns on investment can be a long time in coming (see VCs Are Wary of Cleantech).

Another concern is the need for entrepreneurs in this segment to be involved in government policy, a task that is distasteful to many Valley businesspeople.

“The big concern I have about investing in clean technology companies is the dependence on government policy and subsidization,” said Accel’s Mr. Wagner.

And that’s where he differs from Mr. Doerr’s philosophy. Once a registered Republican, Mr. Doerr now speaks the language of Democrats. And he says entrepreneurs should not be afraid anymore of engaging with the government.

“You can sit back in your garage and do this stuff,” he said.

And then he gets back to his pitch. “We are in the right place and this is the biggest opportunity in the future for a VC,” he said. “We have to find a way to revolutionize the energy industry and get the enabling technology that makes it efficient.”