As at December 31, 2016 As at December 31, 2015
  Historical cost Revaluation adjustments Carrying amount Historical cost Revaluation adjustments Carrying amount
Materials, including 979 (52) 927 1,067 (103) 964
Renovation materials 664 (33) 631 643 (80) 563
Coal 232 - 232 307 - 307
Mazut 15 - 15 14 - 14
Investment materials 14 - 14 16 - 16
Other materials 54 (19) 35 87 (23) 64
Energy origin rights, including: 602 (35) 567 831 (17) 814
Green energy origin rights 388 (33) 355 681 (14) 667
Yellow energy origins rights 148 (2) 146 113 (2) 111
Other energy origin rights 66 - 66 37 (1) 36
Merchandise, including: 44 (10) 34 66 36 102
CO2 emission rights 37 (8) 29 60 38 98
Other merchandise 7 (2) 5 6 (2) 4
Other inventories 68 - 68 79 - 79
TOTAL INVENTORIES 1,693 (97) 1,596 2,043 (84) 1,959

  Year ended December 31, 2016 Year ended December 31, 2015
REVALUATION ADJUSTMENT FOR INVENTORIES AS AT JANUARY 1 (84) (63)
Fair value of CO2 emission rights (46) (42)
Impairment allowance raised (52) (55)
Impairment allowance reversed 66 58
Impairment allowance used 16 19
Other 3 (1)
REVALUATION ADJUSTMENT FOR INVENTORIES AS AT DECEMBER 31 (97) (84)

CO2 emission rights recognized in the inventories include the rights classified as held-for-sale. These rights are presented at fair value. Change in valuation of these rights in the reporting period should be analyzed together with the revaluation of forward contracts (as presented in note 7.4.1 of these consolidated financial statements).

Creation of impairment allowances related mainly to spare parts and materials as a result of their amortization or obsolescence.

As described in note 25.5 of these consolidated financial statements, PLN 51 million of inventories constituted a collateral for the repayment of liabilities or contingent liabilities.