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Note 4 - Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands | Jun. 30, 2022 | Dec. 31, 2021
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Property, plant and equipment, net | $ 177,420 | $ 173,816
Computer Equipment [Member] |  |
Property, plant and equipment, gross | 633 | 633
Furniture and Fixtures [Member] |  |
Property, plant and equipment, gross | 549 | 464
Leasehold Improvements [Member] |  |
Property, plant and equipment, gross | 101 | 101
Excluding Construction in Progress [Member] |  |
Property, plant and equipment, gross | 1,283 | 1,198
Less: accumulated depreciation | (933) | (844)
Property, plant and equipment, net | 350 | 354
Construction in Progress [Member] |  |
Property, plant and equipment, gross | 177,070 | 173,462
Construction in Progress [Member] | Rio Grande [Member] |  |
Property, plant and equipment, gross | 156,053 | 152,445
Construction in Progress [Member] | Rio Bravo [Member] |  |
Property, plant and equipment, gross | $ 21,017 | $ 21,017

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