v3.20.4
Summary of Significant Accounting Policies (Tables)
12 Months Ended
Dec. 31, 2020
Accounting Policies [Abstract]  
Schedule of inventories
Inventories consisted of the following:
 December 31,
(in thousands)20202019
Finished goods$9,815 $17,612 
Raw materials152 243 
Parts, supplies and other32,382 30,441 
   Total Inventories$42,349 $48,296 
Schedule of lives used in computing depreciation for depreciable assets and components of property, plant and equipment, net The lives used in computing depreciation for significant asset classes are as follows:
Asset
Range of Useful
Lives, in Years
Land and improvements
10 to 30
Buildings and improvements
3 to 30
Automotive equipment
5 to 30
Machinery and equipment
2 to 30
Other
3 to 10

Property, plant and equipment, net consisted of the following:
December 31,
(in thousands)20202019
Machinery and equipment$1,388,735 $1,378,651 
Buildings and improvements17,598 17,221 
Automotive equipment16,608 16,691 
Land and improvements14,132 14,075 
Construction in progress12,098 5,198 
Other1,721 1,752 
1,450,892 1,433,588 
Less: Accumulated depreciation553,045 481,629 
     Total Property, plant and equipment, net$897,847 $951,959