Waste
Waste is input material lost during production with no recovery value at all, such as evaporation or dust, unlike scrap, which can still be sold for something, however small the amount.
What it is
See it move
A chemical process starts with 500 kg of raw material. Heating evaporates 20 kg of solvent, which has no market value at all — waste, not scrap. The remaining 500 − 20 = 480 kg becomes saleable product. Because waste has zero recovery value, its cost is absorbed entirely into the 480 kg of good output that survives.
Check yourself
A food processor starts with 800 kg of raw vegetables. During preparation, 60 kg is lost to trimmings with no market value at all, and a further 40 kg of trimmings is sold to a livestock feed supplier for a small amount. How many kilograms should be classified as waste, and how many as scrap?