I, of course, don't know where you are. Here in Seattle I would give it to a local High School Photo OR Arts dept. A write off for sure or even a grant if you can support it.
As for disposal, here, call the solid waste dept for instructions; they will get rid of it for you if you will deliver it for them to do so. In Missouri where I grew up; throw it over the rail of the Missouri River Bridge.
You can't be the only one who has this unit; if this serves you well, can you find the resources to acquire the supplies you need from the other users who have used this unit but no longer want to. Or is that may be what you are trying to do.