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Energy and Related Sales, Net (Tables)
 12 Months Ended
Dec. 31, 2017
Text Block [Abstract]  
Summary of Energy and Related Sales Net

The following table summarizes this activity for each of the past three years:

 

 

Year ended December 31

 

 

In thousands

2017

 

 

 

2016

 

 

2015

 

 

Energy sales

$

3,258

 

 

 

$

3,613

 

 

$

5,315

 

 

Costs to produce

 

(3,986

)

 

 

 

(3,972

)

 

 

(4,428

)

 

Net

 

(728

)

 

 

 

(359

)

 

 

887

 

 

Renewable energy credits

 

5,854

 

 

 

 

6,500

 

 

 

4,777

 

 

Total

$

5,126

 

 

 

$

6,141

 

 

$

5,664