Iron granules are separated from dust particles by using a magnet. The 'magnetic field' of the magnet will influence the iron granules that gets magnetized and attracted to the magnet.
There are several types of renewable resources that can be used in our home. Solar power, wind power, water power to name a few. The most reliable would most likely be water, since the winds don't always blow and the sun doesn't always shine, but water always flows.