Hi Suhant
Actually co-product concept is used when all the products are mandatory to be produced in the process means you can't avoid any product to produce. Basically in chemical industry or in a tar industry when you process any chemical some co-products with main product will be produced and thats why this apportionment structure is used.
In your case it is not that type of process..so you could make it By-product method of process instead of co-product. Then this could be avoided.
Kamal