Spain has a high number of pig farms, with about 25 million pigs bred in the country. Most of the farms are concentrated in the regions of Catelonia, Castilla La Mancha, Castilla Leon or Murcia. This concentration results in water pollution, due to excessive nutrients being land applied. As pig manure is a problem in Spain -- producing pigs is for the famous ham only but there is no farming activity around and therefore no demand/possibility of using the manure as fertilizer -- the heat produced from the engines is used for drying the manure in order to reduce the quantity and the problem. Companies began selling pig manure drying processes that utilized natural gas. All the processes have to burn natural gas, which isn't renewable. However, the Central Government of Spain's special tariffs also include biogas from anaerobic digestion. In 2009, SENER installed two Valpuren plants, one in Polan and one in Consuegra, both in the Toledo region of Castilla La Mancha. SENER utilized the Entec anaerobic digestion technology at the facilities.