Kenya’s Nzambi Matee beams brightly, thrusting a brick forth to coincide with the click of the camera. It is no ordinary brick – the entire thing is made from plastic waste – and no ordinary photo, either. Behind her, stands the Deputy Secretary-General of the United Nations, Amina Mohammed. Ms. Mohammed rests her hands on Nzambi’s shoulder, undoubtedly proud of her. Around her are a dozen other young environmental advocates.