cardboard caskets definately do exist, I’ve seen them mentioned by morticians, and advertised, and they don’t neccecarily look or work badly. then there are woven willow basket type caskets.

And then, this one is perhaps most similar to you the option you cite as a preference, there’s the classic shroud. basically some plain woven fabric that the bidy is wrapped in. the lightest, lest resource intensive, and likely lest expensive body covering for a funeral, that i can think of. shrouds seem popular in green and natural butials, as well as a number of religious burials, and they have a history of sucessfully us that goes back some way it seems.

It’s not neccecarily quite the same as used carpet, but you could probably arrange for a plain second hand sheet, or an old curtain perhaps, for your funeral if you wanted. Just make sure its biodegradable and large enough to cover a body, and you should be good (actually if you can find old carpet that meets those conditions, they might just accept that too, probably wnat to check with the burial grind staff ahead of time though).

In quite a similar spirit, perhaps, anyway. Then, with a coevring picked out, you’ll probably wnat a local green or natural burial ground, as the likeliest place for a burial place that’s up for that style of burial and coffin alternative.