|Millions of euro|
|at Dec. 31, 2020||at Dec. 31, 2019||Change|
|Raw and ancillary materials, and consumables:|
|- materials, equipment and other inventories||1,542||1,493||49||3.3%|
|- CO2 emissions allowances||159||96||63||65.6%|
|- green certificates||5||12||(7)||-58.3%|
|- white certificates||7||1||6||-|
|Buildings held for sale||52||54||(2)||-3.7%|
|Payments on account||41||18||23||-|
Raw and ancillary materials, and consumables consist of materials and equipment used to operate, maintain, and construct power plants and distribution networks, as well as fuel inventories to cover the Group’s requirements for generation and trading activities.
The change in the year is mainly attributable to the write-down of inventories of fuel and materials associated with plants subject to impairment, primarily in Italy and Chile, as a result of the energy transition process begun by the Group. Other factors include the reduction in inventories in Russia following the disposal of the Reftinskaya GRES plant in the final Quarter of 2019. These developments were partially offset by an increase in CO2 emissions allowances in Spain as a result of a decrease in the compliance obligation as a result of the reduction in high-emissions generation.