Strange-looking synthetic trees that suck carbon dioxide out of the air. Algae that can turn into gas. A candy factory fueled by methane from a local dump.
These examples may sound bizarre, but all are potential moneymakers.
It's the unlocked potential of these eco-friendly ideas that has many saying that the government should spend taxpayer dollars on "going green."
At an Earth Day celebration in Newton, Iowa, today, President Obama said the United States must lead the world in renewable energy. He said his energy plan would simultaneously help the environment and the economy.
"The choice we face is between prosperity and decline," Obama said. "The nation that leads the world in creating new sources of clean energy will be the nation that leads the 21st century global economy."
In the middle of the worst recession since the Great Depression, skeptics question the wisdom of spending billions of dollars to fight global warming.
Proponents of the spending, on the other hand, argue that by investing in technologies like wind and solar energy, the government can create millions of jobs.
"This is precisely the time to invest in solutions because those investments are actually going to help us get out of the downturn that we're in," said Jeffrey Sachs, executive director of the Earth Institute at Columbia University.
Representatives of more than 175 companies, including the snack food company Mars Inc., are meeting in California at the Fortune Brainstorm Green to talk about making money by going green.
A Mars Inc. official said the company's new candy factory that runs on methane is saving $500,000 a year.
"We believe that proves being green can be more profitable," said Brian Camastral, president of global food for Mars Inc. "We feel we have the responsibility to take leadership actions and to tell people about the success we're having so they can see why going green makes sense."
But, some disagree.
Steven Hayward, a scholar at the American Enterprise Institute who testified before Congress Wednesday, said in order for the U.S. to truly take on climate change, it would have to be more expensive for Americans to gas up their cars and power their homes.
"When you make a major factor of production, like energy, more expensive in a time of a recession, you will probably prolong the recession by a certain amount," Hayward warned.
Proponents of tackling climate change now say that while making gas and coal more expensive might be painful for the consumer, it will also create a stream of new industries that will ultimately promote economic growth.
For example, consider the fake trees that suck up carbon dioxide out of the atmosphere. Inventor Klaus Lackner said the synthetic trees are nearly 1,000 times more effective than real trees are at removing carbon dioxide from the environment.
Lackner argued that synthetic trees could become a $1 trillion-per-year industry if the government decides to crack down on carbon emissions.
"The government has done this in other cases," he said. "The governments of the world many, many decades ago said sewage in the streets is not acceptable. And so now we have an industry around taking care of sewage. ... Nobody in his right mind would say, 'I don't want to be a part of this and I'll just throw stuff in the street. CO2 is another waste product."