Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 37,579	$ 15,736
Investment securities	0	62,207
Prepaid expenses and other current assets	878	859
Total current assets	38,457	78,802
Property, plant and equipment, net	150,051	134,591
Operating lease right-of-use assets, net	1,004	1,054
Other non-current assets, net	13,917	6,748
Total assets	203,429	221,195
Current liabilities
Accounts payable	519	11,912
Share-based compensation liability	182	182
Accrued liabilities and other current liabilities	1,294	8,751
Current operating lease liabilities	638	698
Total current liabilities	2,633	21,543
Non-current common stock warrant liabilities	4,261	12,034
Non-current operating lease liabilities	166	3
Other non-current liabilities	15,000	0
Total liabilities	22,060	33,580
Commitments and contingencies (Note 13)
Stockholders’ equity
Common stock, $0.0001 par value Authorized: 480.0 million shares at June 30, 2020 and December 31, 2019 Issued and outstanding: 117.5 million shares and 117.3 million shares at June 30, 2020 and December 31, 2019, respectively	12	12
Treasury stock: 177,549 shares and 137,860 shares at June 30, 2020 and December 31, 2019, respectively, at cost	(796)	(685)
Preferred stock, $0.0001 par value Authorized: 0.9 million, after designation of the Series A and Series B Convertible Preferred Stock Issued and outstanding: none at June 30, 2020 and December 31, 2019	0	0
Additional paid-in-capital	215,807	224,091
Accumulated deficit	(138,573)	(133,701)
Total stockholders’ equity	76,450	89,717
Total liabilities, Series A and Series B Convertible Preferred Stock and stockholders’ equity	203,429	221,195
Series A Convertible Preferred Stock [Member]
Current liabilities
Series A Convertible Preferred Stock, $1,000 per share liquidation preference Issued and outstanding: 61,743 shares and 58,197 shares at June 30, 2020 and December 31, 2019, respectively	51,727	48,084
Series B Convertible Preferred Stock [Member]
Current liabilities
Series A Convertible Preferred Stock, $1,000 per share liquidation preference Issued and outstanding: 61,743 shares and 58,197 shares at June 30, 2020 and December 31, 2019, respectively	$ 53,192	$ 49,814