This is Munters media, an absorbent cellulous material that's used to cool and humidify warm desert air brought into the chamber through vanes and filters. Air passes through the material and is cooled by a small amount of water. The air cools by 10 to 12 degrees as it uses energy to absorb water vapor. Water is collected and sent to an ultraviolet exposure chamber to kill bacteria and other living organisms, then recirculated through the Munters Media. Humidification is necessary in the data center because the dry desert air, particularly during winter, encourages static electrical discharges that can be harmful to data center equipment.
Facebook's Prineville facility won the Engineering News-Record's award for best green building in 2011, due in no small part to its energy and water-conserving features in a region where energy is plentiful but water is scarce.