Scrap tyres would be burned to fuel a cement plant run in the Pueblo-area under plans proposed by the facility’s owner, Grupo Cementos de Chihuahua (GCC).

The method also provides a partial solution to a major problem: how to deal with the 300 million car and truck tires discarded every year in the US.

But it also is creating concern among some Pueblo residents and environmentalists who fear that burning tyres will produce odors and toxic emissions.

"It’s really like burning hazardous waste," said Ross Vincent, chairman of the Rocky Mountain Sierra Club’s Pueblo-based regional arm. "We think fundamentally that it’s a bad idea."

Not so, say officials of the plant’s Mexican owner, GCC and its Denver-based subsidiary, GCC of America.

Burning tires, they say, actually is cleaner than combustion of other fossil fuels and helps reduce landfill use.

Opponents and proponents cite studies and anecdotal information in support of their claims. Yet little peer-reviewed independent research exists for a business practice that has become prevalent only over the past decade.

GCC recently purchased for US$2m the Midway tire landfill south of Fountain as a potential source for the cement plant.

Officials of GCC said they have no immediate plans to burn tyres, calling the idea a "medium-term project" that would involve filing for state and local zoning and air-quality permits.

The US$300m cement facility southeast of Pueblo began operations last year and has been using coal in conformance with existing permits.