To ensure purity, all production had to be above ground, in an immaculately clean plant free of chemical contamination.

As a result, experts caution, it is hard for consumers to know whether the meat they buy comes from the cleanest plants.

Regarding the new, advanced coal technology we intend to use, these plants will be 80 percent cleaner than today's average United States coal plant.

In some cases, it may even pay utilities to subsidize customer conservation rather than build cleaner plants or buy the right to pollute from someone else.

It was a large, clean, new plant in a crowded, dirty, old industrial neighborhood.

That puts the newer, cleaner but more expensive gas-fired plants at a competitive disadvantage.

It would only be used for the next few years, or until newer, cleaner plants begin operation.

Instead of building new, cleaner plants, many companies simply patched and upgraded their old, dirty plants.

A dirty plant can buy pollution rights from a clean plant, for example.

In fact, they are the cleanest plants possible because there is no environment variable and the dirt in the food supply is extremely limited.