Note 6 - Property, Plant and Equipment (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

Property, Plant and Equipment [Table Text Block]

	Useful Life		March 31,			December 31,
	(in years)		2021			2020
Luverne retrofit asset		20	$	70,820		$	70,820
Plant machinery and equipment		10		17,374			17,374
Site improvements		10		7,157			7,157
Lab equipment, furniture and fixtures and vehicles		5		6,396			6,396
Demonstration plant		2		3,597			3,597
Buildings		10		2,543			2,543
Leasehold improvements, pilot plant, land and support equipment		2 to 5		2,523			2,523
Computer, office equipment and software		3 to 6		2,021			1,983
Construction in progress		—		18,525			13,132
Total property, plant and equipment				130,956			125,525
Less accumulated depreciation and amortization				(60,260	)		(59,117	)
Property, plant and equipment, net			$	70,696		$	66,408

Schedule of Depreciation and Amortization Expense [Table Text Block]

	Three Months Ended March 31 ,
	2021		2020
Cost of goods sold	$	1,088	$	1,587
Operating expenses		56		56
Total depreciation and amortization	$	1,144	$	1,643