Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 36,743	$ 22,608
Prepaid expenses and other current assets	883	670
Total current assets	37,626	23,278
Property, plant and equipment, net	170,431	161,662
Operating lease right-of-use assets, net	727	429
Other non-current assets, net	19,903	16,299
Total assets	228,687	201,668
Current liabilities
Accounts payable	744	207
Share-based compensation liability	182	182
Accrued liabilities and other current liabilities	5,306	1,032
Current common stock warrant liabilities	1,330	3,290
Current operating lease liabilities	579	432
Total current liabilities	8,141	5,143
Non-current common stock warrant liabilities	2,463	874
Non-current operating lease liabilities	169	0
Other non-current liabilities	23,000	22,916
Total liabilities	33,773	28,933
Commitments and contingencies (Note 13)
Stockholders’ equity
Common stock, $0.0001 par value Authorized: 480.0 million shares at September 30, 2021 and December 31, 2020 Issued and outstanding: 120.7 million shares and 117.8 million shares at September 30, 2021 and December 31, 2020, respectively	12	12
Treasury stock: 344,459 shares and 249,742 shares at September 30, 2021 and December 31, 2020, respectively, at cost	(1,310)	(1,031)
Preferred stock, $0.0001 par value Authorized: 0.8 million, after designation of the Convertible Preferred Stock Issued and outstanding: none at September 30, 2021 and December 31, 2020	0	0
Additional paid-in-capital	195,136	209,481
Accumulated deficit	(162,046)	(148,030)
Total stockholders’ equity	31,792	60,432
Total liabilities, convertible preferred stock and stockholders’ equity	228,687	201,668
Series A Convertible Preferred Stock [Member]
Current liabilities
Convertible Preferred Stock	61,614	55,522
Series B Convertible Preferred Stock [Member]
Current liabilities
Convertible Preferred Stock	62,542	56,781
Series C Convertible Preferred Stock [Member]
Current liabilities
Convertible Preferred Stock	$ 38,966	$ 0