Dave Guilford, from Automotive News.

There are an estimated 835 million motor vehicles on the world’s roads, according to J.D. Power and Associates.

The big number — global vehicle count — is expected to swell from today’s 835 million to 1.1 billion within 15 years. That would be an increase of 265 million vehicles — more than the total number on U.S. roads today.

Other industry sages see similar growth. Garel Rhys, director of the Centre for Automotive Industry Research at Cardiff University in Wales, predicts that the industry will crank out more vehicles in the next 20 years than the 1.8 billion it built in its first 110 years.

But we have to look at what is visible today. What we can see coming vastly increases the pressure to replace petroleum-fueled engines with fuel cells, ethanol, electric vehicles, compressed natural gas or some combination of those.

As Larry Burns, General Motors’ fuel cell point man, put it recently, “We really have to ask ourselves, can the world sustain 1 billion automobiles?“

If they all burn petroleum, probably not.