It was now packed inside the beaded bag, which, Harry was impressed to learn, Hermione had protected from the Snatchers by the simple expedient of stuffing it down her sock.
Was it a) he wanted to impress his girlfriend, b) he was sick of breathing in the city's car fumes, or c) he was late for his lecture because of a flat tyre?
While they admire the aspiration, if we had come up with a purpose line that was solely about environmental sustainability, it would have been dead on arrival.