"Oooh, these ropes have had it, they're 8 years old and need replacing."
Get your arts and craft on http://www.roperugs.com/
But since you appear to live in Germany perhaps you can recycle them there?
I just donated a couple of old ropes to the local beavers and scouts groups, under the very clear understanding that they were not for climbing with any more. They were really happy to take them for knot practice, making bivis etc. Worth a shot?
I've got a hardly-used, ~15 year old rope (probably a 10.5 or 11 mm Mammut if memory serves) that's been sat in my parents' garage for most of that time. Is it any good to use for anything, or is it one for the rug weavers?
[Do unused ropes actually degrade over time?
Nylon supposedly loses upto 50% of strength over 10 years. Mountain Training guidance is to bin ropes even if unused and in original packaging at this age.
There's this UIAA document on ageing of ropes: https://www.theuiaa.org/documents/safety/About_Ageing_of_Climbing_Ropes.pdf
Ageing caused only by storage can almost be neglected compared with ageing during use.
These facts also hold for 10- or even 15-year-old ropes. This has been proved by many tests of such old ropes (not even 25-year-old ropes and one 30-year-old rope broke in tests...
A rope need only be discarded when the the sheath has been damaged such that the core is visible.
I’d be totally happy to use a 15 year old rope stored in a cool dry cupboard in my home. The BD study (one data point) more or less confirms this. I’ll try to find the link but IIRC Beal recommends a rope could be used for up to 10 years after sitting unused for 5 years. You can be sure they are being cautious. Storage in someone else’s garage might be a concern. Are you completely confident it’s been nowhere battery acid for example?
I'm currently using a old single rope at the climbing wall. I started using it after my short gym rope got too short to lower off with.It must be the best part of fifteen years old.I had a brief review of the reports linked to above and decided there seemed no evidence it needed retiring. It has not broken yet.