They solved that one here as well, using a copper plated spring steel conductor in the bundle. The scrap yards will not take the cable as the spring steel will break the cutters they use on cable to get them short enough to bale, and removing the steel from the cable is a long job. plus it is near impossible to cut with either a hacksaw or bolt cutters.
I gave a suggestion to simply use a 25mm diameter steel cable instead, it will still do the job, but is a lot harder to cut.