Food product      Protein by-product (1 kg protein)                 - 1 kg protein        Animal products - 0.5 kg soy oil 0.5 kg rape oil   Margarine etc. 0.25 kg protein                          …and so on   By iteration, it can be calculated that 1 kg of raw protein in a food industry by-product requires the following system expansion: a reduction in volume of soy protein of 1 + 0.25 + 0.25² +0.25³ + …. = 1.33 kg raw protein, which is equivalent to 3.9 kg soy beans (at a protein content of 34%), and an increase in rape production of 0.25 + 0.25² +0.25³ + …. = 0.33 kg raw protein, which is equivalent to 1.66 kg rapeseed (at a protein content of 20%). Food prod. I₁ Soy prod. Animal husbandry I₂ Rape prod. Edible oil production I₁