scrap Costing calculation issues

Dear All,

 3 items like Item_A, Item_B, Item_c are  in Different Bom lines. All these items are facing same problem As below

Each of the standard drums weights 190kg . When we dispense material from the drum an estimated 4 kgs remains in the drum so our loss factor is  2.1% (=4/190). I want AX to automatically cost this waste as part of a batch. The actual weights required per batch must not change as this is part of the formulation

if any one suggest me how i can solve the issue

Thanks in advance.

Regards,

Tarak