Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 40,595	$ 22,608
Prepaid expenses and other current assets	763	670
Total current assets	41,358	23,278
Property, plant and equipment, net	168,176	161,662
Operating lease right-of-use assets, net	860	429
Other non-current assets, net	18,695	16,299
Total assets	229,089	201,668
Current liabilities
Accounts payable	200	207
Share-based compensation liability	182	182
Accrued liabilities and other current liabilities	4,277	1,032
Current common stock warrant liabilities	9,168	3,290
Current operating lease liabilities	504	432
Total current liabilities	14,331	5,143
Non-current common stock warrant liabilities	3,068	874
Non-current operating lease liabilities	333	0
Other non-current liabilities	23,000	22,916
Total liabilities	40,732	28,933
Commitments and contingencies (Note 12)
Stockholders’ equity
Common stock, $0.0001 par value Authorized: 480.0 million shares at June 30, 2021 and December 31, 2020 Issued and outstanding: 118.5 million shares and 117.8 million shares at June 30, 2021 and December 31, 2020, respectively	12	12
Treasury stock: 300,493 shares and 249,742 shares at June 30, 2021 and December 31, 2020, respectively, at cost	(1,171)	(1,031)
Preferred stock, $0.0001 par value Authorized: 0.8 million, after designation of the Convertible Preferred Stock Issued and outstanding: none at June 30, 2021 and December 31, 2020	0	0
Additional paid-in-capital	199,553	209,481
Accumulated deficit	(163,268)	(148,030)
Total stockholders’ equity	35,126	60,432
Total liabilities, convertible preferred stock and stockholders’ equity	229,089	201,668
Series A Convertible Preferred Stock [Member]
Current liabilities
Convertible Preferred Stock	59,509	55,522
Series B Convertible Preferred Stock [Member]
Current liabilities
Convertible Preferred Stock	60,549	56,781
Series C Convertible Preferred Stock [Member]
Current liabilities
Convertible Preferred Stock	$ 33,173	$ 0