If you are working with biological materials it is extremely difficult to keep sterile for mass production. If you just want a small little room of it, feasible. You want 100 acres of it? You're gunna get a hole or leak or single contamination and now you need to resterilize 100 acres of material.

Basically the problem is sterilization doesn't get easier at scale; which is the same problem many other biological technologies suffer like artificial photosynthesis or pesticide-free indoor farming. Eventually something gets in that isn't suppose to and you have a perfect feasting ground for pests, free of any competition.