Note 6 - Property, Plant and Equipment (Tables)

9 Months Ended

Sep. 30, 2021

Notes Tables

Property, Plant and Equipment [Table Text Block]

	Useful Life			September 30,			December 31,
	(in years)			2021			2020
Luverne retrofit asset		20		$	70,820		$	70,820
Plant machinery and equipment		10			17,949			17,374
Site improvements		10			7,157			7,157
Lab equipment, furniture and fixtures and vehicles		5			6,935			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	7		2,523			2,523
Computer, office equipment and software	3	to	6		2,240			1,983
Construction in progress		—			51,033			13,132
Total property, plant and equipment					164,797			125,525
Less accumulated depreciation and amortization					(62,634	)		(59,117	)
Property, plant and equipment, net				$	102,163		$	66,408

Schedule of Depreciation and Amortization Expense [Table Text Block]

	Three Months Ended September 30,
	2021		2020
Cost of goods sold	$	1,098	$	1,418
Operating expenses		96		52
Total depreciation and amortization	$	1,194	$	1,470

	Nine Months Ended September 30,
	2021		2020
Cost of goods sold	$	3,358	$	4,580
Operating expenses		198		158
Total depreciation and amortization	$	3,556	$	4,738