The NAAQS goals of health-based standards for the quality of ambient air are designed to ensure that the air everywhere in the U.S. is fit to breathe. Locations throughout the country are classified as either "in attainment" or "nonattainment" for a given pollutant. Find out if your location's status here.
Deploying CHP technologies in nonattainment areas can be significantly harder due to stricter air quality permitting rules on certain equipment such as large engines. Currently, emissions limits are input-based, that is, they have been established on a unit of pollutant emitted per unit of fuel input (lb/MMBtu) basis. This approach relies on the application of pollution control devices to reduce emissions and does not explicitly recognize the efficiency of the process in converting fuel input into a useful output. As such, input-based regulations do not encourage pollution reductions through energy efficiency.
The goal of output-based regulations (OBR) is to encourage the use of fuel conversion efficiency and renewable energy as air pollution control measures. OBR level the playing field by establishing performance criteria and allowing efficiency and renewable energy to compete on equal footing with any other method of reducing emissions, such as combustion controls and add-on controls.
Comparing different energy generation facilities is easy and clear when they are permitted on an output-basis, as demonstrated below. The input-based emissions limits stated on the left provide a limited indication of the actual emissions impact of the plants, while the limits on the right directly correlate to the actual emissions impact of the plants.
Source: U.S. EPA CHP Partnership website