Calculating return on investment is not as simple as using costs and savings to determine a payback period on a capital investment. Today, greenhouse-gas reporting has changed the picture. Not only does a plant have to consider the capital cost, but also its effect on the facility's carbon footprint.

Catalytic Products International, Lake Zurich, Ill., has a gas-saving estimator on its website to help users calculate the return on investment (ROI) of a new or replacement air pollution control system or energy recovery system in terms of financial savings and greenhouse gas emission reductions.

To use the calculator, go to