The term byproduct refers to an incidental or secondary product, different from the intended or primary product, resulting from a manufacturing process or chemical reaction. A byproduct may or may not be wanted, or considered to be marketable or waste.
See also:
"Byproduct" is in the NAICS Code "311613"
(Rendering and Meat Byproduct ProcessingTallow produced in rendering plant)
Ref: 120955/2006-10-03