as much as possible before it comes aboard. Remove all boxes, etc, repackage the contents into baggies, sometimes four or five sealed packages to a baggy. Those baggies get washed and reused if needed. I put any instructions in the bag with the product. Pre mix any dried ingredients into baggies also, such as bread making , pancake mix, etc. Powdered milk also.

As an ex backpacker, I still try for the mentality that if I could carry the full whatever IN, I could sure carry the empty OUT.

Try hard to not buy stuff in cans (such as tuna fish) much easier to store the foil pouches, after a wash out. Besides, the stuff is MUCH better in those..When I was out full time, varieties of meats were canned aboard, in half pint containers, each of which made A meal. Those when empty got washed out and restowed. All were wrapped in old socks

As much as possible gets disposed of in an approved container right there at the dock.

Paper such as paper towels, get torn into bits and wet out, then put over. Other wise, NOTHING other than food scraps goes overboard. No foil, no cans, no other paper. Most certainly NOT plastic. I HAVE burned paper on a beach, below a tide line, so the next tide erased the ashes. But not often.

I don't refrigerate much of anything other than drinks aboard by the way. Try to cook for zero leftovers

Sadly, here where I live, recycling, as a community thing, is a non starter so far.