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The first general metric for green chemistry remains one of the most flexible and popular ones. Roger A. Sheldon’s environmental factor (E-factor) can be made as complex and thorough or as simple as desired and useful. [10] The E-factor of a process is the ratio of the mass of waste per mass of product:
An emission intensity (also carbon intensity or C.I.) is the emission rate of a given pollutant relative to the intensity of a specific activity, or an industrial production process; for example grams of carbon dioxide released per megajoule of energy produced, or the ratio of greenhouse gas emissions produced to gross domestic product (GDP).
The factors help to estimate emissions from various sources of air pollution. In most cases, the factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages. The equation for the estimation of emissions before emission reduction controls are applied is: E = A × EF
A great many computer programs for calculating the dispersion of air pollutant emissions were developed during that period of time and they were called "air dispersion models". The basis for most of those models was the Complete Equation For Gaussian Dispersion Modeling Of Continuous, Buoyant Air Pollution Plumes shown below: [4] [5]
As an example, a measured NO x concentration of 45 ppmv in a dry gas having 5 volume % O 2 is: 45 × ( 20.9 - 3 ) ÷ ( 20.9 - 5 ) = 50.7 ppmv of NO x. when corrected to a dry gas having a specified reference O 2 content of 3 volume %. Note: The measured gas concentration C m must first be corrected to a dry basis before using the above equation.
Vacuum emission from metals tends to become significant only for temperatures over 1,000 K (730 °C; 1,340 °F). Charge flow increases dramatically with temperature. The term thermionic emission is now also used to refer to any thermally-excited charge emission process, even when the charge is emitted from one solid-state region into another.
Spontaneous emission is ultimately responsible for most of the light we see all around us; it is so ubiquitous that there are many names given to what is essentially the same process. If atoms (or molecules) are excited by some means other than heating, the spontaneous emission is called luminescence. For example, fireflies are luminescent.
Radiative forcing is defined in the IPCC Sixth Assessment Report as follows: "The change in the net, downward minus upward, radiative flux (expressed in W/m 2) due to a change in an external driver of climate change, such as a change in the concentration of carbon dioxide (CO 2), the concentration of volcanic aerosols or the output of the Sun." [3]: 2245