Shellac is a natural finish, using denatured alcohol only as a vehicle that meets Gov. requirements. Any alcohol would work. Best thing about using shellac is that you can buy bulk flakes(which have a very long shelf life) and mix your own mixes and colors.

Another plus is shellac will dry in as short a time as 15 minutes.

The minus is that allowing alcohol to touch a shellac finish will dissolve that part of the finish. The plus to that minus is that using shellac to repair is the best way to fix the damage.

I'd just like to know what you consider "eco-friendly" and "environmentally sustainable" and what is not. Are you concerned for the exposure of your workers, restricted by government what you can apply (or obtain) in your shop, or just want to have an "eco-friendly" green label on the product?

All natural and eco friendly are really two different animals, especially for paints and wood coatings.

For marketing your "eco friendly" "environmentally sustainable" products, look into green label paints, zero VOC, or contain recycled content.

My personal favorite green label wood finish is Sierra from Rustoleum. It is as durable as catalyzed lacquer, has no VOC's, and dries to a true clear without the whitish or blueish hue, which is problematic for many water-based clear wood coatings.

Here is a link that might be useful: sierra

I also work with reclaimed wine barrels and Tung oil works really well for me. It can be a little pricey and hard to find though. You don't need to use very much at a time so a quart can last a while.
Make sure to get "pure tung oil" versus "tung oil finish" which usually has distillates and other not-so-friendly things in it.
It's available at Rockler retail stores and online.

" You don't need to use very much at a time so a quart can last a while."

Real Tung oil must be stored in a container with no air. Any amount of air will cause the tung oil to gel, and then harden by polymerization. Once it does, that's it. You can't thin it down with solvent.

Woodcraft sells pure Tung oil. It comes in a plastic container, so you can squeeze out the air until it's about half empty. Then I transfer it to a smaller plastic container, and always make sure to squeeze out all the air before closing it up.

That being said, I have some 3 or 4 year old Tung oil that's still liquid and ready to use.

Tung oil is not a very durable finish, and it takes a long time for it to harden. I have used Waterlox varnish as a top coat over base coats of tung oil, with excellent results. I was basically experimenting with Tung oil, and eventually decided that a more durable finish was necessary. I let the Tung oil dry for a couple of weeks before using the Waterlox Varnish. The resulting finish looks almost identical to using pure varnish, but there is less ambering of the Birch and Maple woods.

Absent a legal definitional of "eco-friendly" and "environmentally sustainable" you can call it whatever you want and do whatever you want.

It does not actually mean anything.

I get a little impatient with people who want "all natural," "eco-friendly," and "sustainable." I would challenge most of these people to pass a ninth-grade science test. In most cases I think they are just being duped out of their money.

Add to the fact that finishing labels rarely tell the whole truth about the contents. Below is a link and at $30 a quart seems like quite the deal.

I have never really understood the fascination, almost cult-like following, of tung oil. It seems to offer no advantages over the much cheaper, faster, easier to use, and less error-prone boiled linseed oil (which is not boiled, another finish label lie). I would challenge anyone to distinguish between the two side by side on the same piece of wood.

I did a fabric cleaning job for a lady a few years ago. She didn't want me to use any "chemicals." I'm thinking, that leaves light or vacuum, because everything else, including Di-hydrogen Monoxide (aka water) is a chemical. She was pleased when I pulled out a jar of "Natural Fiber Cleaner." I didn't tell her that "natural" modified "fiber" (it was meant for Haitian cotton) and not "cleaner." The only difference was the pH; it was not as alkaline as the other cleaners.

Here is a link that might be useful: one alternative

"I get a little impatient with people who want "all natural," "eco-friendly," and "sustainable." "

Think of it as a new age religion.
It explains a lot.

You could use Crystal-lac stain and finishes. The stain MSDS sheet says it has 0 VOC's

http://www.mcfeelys.com/crystalac-waterborne

OK, you've convinced me. But I'm a bit confused? Can you explain the difference between a VOC and an HAP?

I've checked some of my finishes for their contents. Which of the following would be classified as a VOC:
* 2-Butoxyethanol
* methyl ethyl ketone
* 2-propanol
* acetone
* dihydrogen monoxide