Let's simply and change the sentence to clarify.
"Collecting metals from electronic waste for reuse and reopening abandoned mines are key components of the urban mining industry."
Here the subject is composed of two gerunds but is clearly plural, and so must take a plural verb. In your original sentence, the two gerunds (collecting and reusing) are part of one process and that one process is the subject of the sentence and so must take a singular verb.
That the sentence is a passive construction ("is called," a form of verb "to be" with a past participle), where the subject receives rather than initiates the action [see http://www.grammar-monster.com/glossary/passive_sentences.htm] does blur the subject's singular nature.