After years of false starts, a new industry selling motor fuel made from waste is getting a big push in the United States, with the first commercial sales possible within months.

Many companies have announced plans to build plants that would take in material like wood chips, garbage or crop waste and turn out motor fuels. About 28 small plants are in advanced planning, under construction or, in a handful of cases, already up and running in test mode.

For decades scientists have known it was possible to convert waste to fuel, but in an era of cheap oil, it made little sense. With oil now trading around $125 a barrel and gasoline above $4 a gallon, the potential economics of a waste-to-fuel industry have shifted radically, setting off a frenzy to be first to market.

If I were, say, the Saudis, I’d try to push prices down just long enough to bankrupt all these new alternative-energy schemes. Then, back over $100 a barrel again.