The sugar mills won't buy sugar juice at the moment. 1) they use the left-over bagasse (fibres) as fuel to run 'steam engines' that power everything else in the mill -- and some mills generate electricity and sell to the grid-power suppliers. 2) recently, mills are diversifying into bagasse products: (plants) potting mix, food fibres, building materials, ... 3) most mills have invested in transportation network (to carry sugar canes whole to the mills), they will protect their investment.

One more point, sugar canes need washing (with water) before crushing and extracting (sugar) cane juice which must go into other (sugar making: crystallizing, refining,....) processes very quickly, otherwise wild yeasts would make some alcohols and mix alcohols in the juice and that is another problem.

In Aus, most cane growers buy shares in sugar mills (hence are part owners of sugar mills), they would see no reason to change. In Thailand, cane growers do not have any part in sugar mills (same as rice growers, corn growers, cassava growers,...) so they situation will improve by "one link" in the long chain (of processes).

How can growers change enough links or control the whole chain? Answers to this may come from cultural and social innovation as well as technological innovation.