Short story was part of a horror anthology that was probably published in the 1990s, but might have been a little bit older. The story was about a boy who works in a factory over the summer and seems to thrive off of the evil feel of the place unlike his coworkers who feel it has bad vibes.
Not a lot actually happened in the story, it was mostly about the mood. I think he spent most of the story shoveling... it might have been coal? I think they spoke about it as being heavy and dark. At the end he stretches, reveling the in the new muscles he had put on over the summer which is where they allude to him having almost fed off the darkness of the place. I remember liking the language.