Mostly the insight into worlds that I'd never crossed paths with before.
The catering businesses, the WVO markets, and the other bio/veggers in general. Learned a tump of things about injection systems, that I probably would never have dabbled in, along with the chemistry of the process, and building the plant.
If someone had told me what it was all about, before I got involved, I wouldn't have believed them, which is probably similar to so many not believing me when I tell them about it. (not often, these days......)
Surprising how many people I thought were pretty clued up, who opened their mouths and told me with absolute authority that what I was doing was illegal, and I'd end up regretting it.
Worked out what a few think of me, when the repeatedly ask me if it's worth it, like I'm a bit simple and would put the effort in for no reward. Eye opening, for sure.
And met a whole load of people involved in other stuff that I never knew existed.
Certainly been one of my better decisions.