SAP PP - By product & Co Product.

                                                        

What is the difference between by-product and co-product and how do you differentiate them in a BOM?

A "co-product" is produced along with a main product and carries equal importance as main product. Whereas a "by- product" is not a planned product and is produced after carrying out the process e.g. ethanol is a by product of a sugar industry need to define both in BOM.