4.1 Atom Economy – quantifying waste in chemical reactions

One way of gauging the efficiency of a chemical manufacturing process and hence its environmental impact is to determine the atom economy for the reaction.

Atom economy – expressed as a percentage – is a sustainability metric that considers every chemical used in a chemical reaction, and the extent to which each is incorporated into the product.

To calculate atom economy, you start from a balanced chemical equation and determine how many atoms of reactant are incorporated into the product, and how many end up as by-products or waste.

The atom economy of a process is quantified by the following formula:

Where the formula mass of a substance is the sum of the average relative atomic masses of each atom in the chemical formula. 

The higher the atom economy, the more efficient is the chemical manufacturing process, and the less waste is produced.