The price of byproducts: Distinguishing co-products from waste using the rectangular choice-of-technologies model

•A new method is presented that incorporates byproducts in an input-output framework.•Byproducts are endogenously defined as co-products or waste, depending on price.•A set of scenarios about distiller’s grains byproducts illustrates this new method.•This method can fulfill many methodological needs for circular economy research.