Granular activated carbon (GAC) is a highly porous form of carbon that is used for various applications, primarily to adsorb or remove impurities, contaminants, and odors from gases or liquids. It is produced by heating carbon-rich materials, such as coal, wood, coconut shells, or peat, to high temperatures in the absence of oxygen, a process known as carbonization or pyrolysis. This creates a network of pores and a large surface area, which makes GAC an excellent adsorbent.