12 Inventories

12 Inventories
  31.12.2010 31.12.2011
  CHF thousands    
  Green electricity certificates 5,704 12,038
  Emissions certificates 4,786 4,138
  Emissions certificates held for trading 4,520 3,158
  Gas 6,950 9,451
  Material inventories 8,194 9,009
  Total 30,154 37,794

Inventories consist of material inventories, gas inventories and certificates, and are valued at the lower of acquisition costs and net realisable value. Certificates that are not necessary for own generation needs and which are held for trading purposes are valued at fair value less selling costs. In the year under review an impairment of TCHF 0 (previous year TCHF 600) was recognised.