The sterile conditions become more fragile and easily contaminatible the larger the batch gets. So they need to increase the size of batches to make it economic

The sterile conditions become more fragile and easily contaminatible the larger the batch gets. So they need to increase the size of batches to make it economically viable, but increasing batch sizes makes it more likely to get contaminated, which kills the whole batch. Then you have to dispose of bio-waste material that has been contaminated in a safe and economic fashion, which is a whole different set of problems.