Those are crusts? I would use a microplane and grate more cheese over my pasta from those "crusts," especially given the cost of imported parmigiano...
Unless you use a non-stick pot, the rinds will leave you with an hours-long soaking and scrubbing mess. To avoid this, put the rinds in cheesecloth. No loss of flavor, lots of saved time in mess and clean-up. A great description (and pictures!) of this recipe is over at the smittenkitchen site. Deb Perelman wrote about this years ago. Credit Deb, who credited Jennifer Perillo. http://smittenkitchen.com/blog/2014/01/parmesan-broth-with-kale-and-whit...
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Most Parmesan, especially the real stuff from Italy, doesn't meet the definition of vegetarian because it was made with natural rennet sourced from calf stomachs. There are cheese producers making similar cheeses in other countries with acceptable substitutes, but I would never make a blanket recommendation to serve Parmesan cheese to vegetarians.
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