How to grow sourdough starter for increased production?
I've only baked at home, not commercially, but something sounds amiss if you're throwing away a ton of starter. [And wow, having a multi-lb starter!]

You throw away starter to keep your starter from getting too big, when you're not baking with it. And I'd hope a commercial bakery is always baking with it.

Example: if your starter is 4lbs and you're keeping half (so feeding 1lb flour, 1lb water), then you discard 2lbs, which you promptly replace with the new flour &amp; water. This keeps your starter at 4lbs consistently. Ideally, that 2lbs removed from the starter is what you'd use for your baking (possibly after doubling it, to feed it). 

You don't have to remove the 2lbs, either. You can just add 2lbs flour + 2lbs water, doubling your 4lb starter to an 8lb starter.