Even though, semantically speaking, perhaps some ingredient is needed which is in addition to the existing precursors for the industrial process, the word you need there is else.
The word else is not strictly for alternatives. It is possible to "(also) want something else." which sometimes means in addition to other things that were previously stated. If also is present, it certainly means that.
A good example is: "There is something else I wanted to ask you." which does not mean that I wasted time asking you the wrong question and that actually I just want the answer to this new one!
Extra is something beyond the norm: "Extra large order of fries with the burger." Note that in the sentence we are examining, "needed" follows the blank space. Something which is extra usually cannot at the same time be needed; this is oxymoronic.
There are exceptions. For instance, "This morning Bob needed an extra cup of coffee to get rolling". In this case we are comparing with other mornings, when that cup is not required, expressing the idea that today's requirement is beyond the usual norm.
In the given question, there is no implied comparison to other times when other industrial processes got started. So there is no basis against against which extra can be considered.