As the planet becomes increasingly covered with concrete, Tarun
Naik says at least some of it could be used to help the
environment rather than hurt it. Some of the negative
consequences are worrisome. The production of one ton of cement,
the paste used to make concrete, creates almost an equal amount
of greenhouse gases. That's more than 1.2 billion tons of carbon
dioxide a year, says Naik, a University of Wisconsin-Milwaukee
engineering professor. Concrete roads and buildings have been
linked to "hot city syndrome," a condition in which temperatures
keep rising in urban areas. There's a direct link between
concrete and global warming, according to Naik, who has spent
decades studying greener alternatives to conventional cement and
concrete. What's more, entire geographical regions of the world
are running out of limestone to make cement, Naik says. "As
limestone becomes a limited resource, employment and
construction associated with the concrete industry will
decline," he wrote in a recent study about the s