| 31.12.2015 | 31.12.2014 | |
|---|---|---|
| Net carrying amount opening balance | 201 633 | 240 521 |
| Self-production | 132 595 | 199 838 |
| Acquisition | 202 520 | 252 197 |
| Redemption of emission rights | (343 575) | (486 472) |
| Impairment loss (-) | 3 580 | (4 451) |
| Other changes | (676) | - |
| Net carrying amount closing balance | 196 077 | 201 633 |
The good performance reflects the optimum use of resources in an increasingly challenging market environment.