It’s only taken 28-year-old CEO Tom Szaky a few years to build TerraCycle into a competitive company with a sustainable mission to turn unrecyclable trash into a wide range of products. Seven years ago, Szaky was in the same place as the students from Temple’s Fox School of Business whom he spoke with Monday. Szaky, part of Fox’s showcase of businesses with sustainable practices, offered advice on start-ups and entrepreneurship using examples from his Trenton-based business, which makes everything from bags to cleaners to shower curtains. "You have to be ridiculously persistent and then you have to really believe in your product," he said.