We can turn grass into milk and have been able to do so for some years.
However, there were many issues to be considered before it was put on the supermarket shelves, not least the cost involved.
In a nutshell, you wouldn't be able to afford the stuff. The equipment necessary to do the job would take up a huge amount of space even before the cost of the equipment was taken into account.
Besides, I doubt the idea will ever see the light of day because apart from anything else, dairy farmers would soon be out of business. Just imagine the uproar it would cause in the farming community.