Thoughtful, perceptive environmentalists are coming to realize some of the panaceas suggested as ways to reduce greenhouse gas emissions are no more than political hot air.

Take one favored technology, biofuels. Along with solar and wind power, they can reduce our reliance on fossil fuels, President Barack Obama has assured us.

But just in time for Earth Day, the biofuels bubble was burst. A government-funded study indicates biofuels made from corn residue release 7 percent more greenhouse gases than petroleum-based gasoline.

Shifting away from conventional gasoline to biofuel made from corn would increase global warming.

That really should not come as news. It already is known some so-called “green” technologies are far from environmentally sound.

Consider the ethanol gasoline additives required by law and subsidized by taxpayers. Ethanol, too, is made from corn. Researchers have found the process of manufacturing it releases enormous amounts of greenhouse gases.

And, of course, there are side-effects such as higher food prices because many corn farmers prefer selling their product to ethanol producers.

No thoughtful person would argue against effective, economical alternative energy sources. But the more scientists and economists learn, the more it seems much of the hype about “renewable” energy is no more than propaganda from special interests.