There are production garbage collectors written in languages like Java, so this shouldn't be surprising.
I wrote a copying collector against a KV store in Clojure that I ran in prod for a while, though I swapped it out for a generational mark and sweep in Java.
I'm sure somewhere, somehow, somebody has written a GC in Excel serving some kind of business need.
As mentioned about though, GC algorithms can be transferred to higher-level system as well. For example, here is a basic Mark-Sweep algorithm implemented in JavaScript on JS objects in a collection: https://gist.github.com/DmitrySoshnikov/4391763