Why not start a black oxide operation?

I worked in a machine shop a few years back that did black oxide in-house. It wasn't that hard, really- the setup was two hotplates, and 5 or 6 steel 5-gallon buckets full of the chemicals. The chemicals that needed to be heated were heated in the buckets they came in on the hot plates, and everything was stored by just putting the lids back on after use. We just did it out on the loading dock for ventilation.

The chemicals were bought from an industrial supplier as a system, and full instructions for each step were printed on the each bucket's label, with a number on each one to ensure that you used the chemicals in the right order.

It only worked for pieces that were small enough to fit in the buckets, obviously, but the finish came out fine.

No idea how tough it would be to deal with EPA issues- the setup I saw was in a place that did a lot of things that were a little shady, so I doubt they were doing anything in particular to minimize environmental concerns. I certainly wouldn't dump the chemicals in your backyard after use!