Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss and comprehensive loss	$ (7,260)	$ (5,971)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	66	66
Amortization of debt discount and issuance costs	1,009	992
Interest expense added to loan principal	2,489	2,361
Interest expense added to lease liability	300	262
Loss on debt conversion		1
Debt conversion expense	197
Compensation charge for stock and share option awards	122	105
Unrealized gain on warrant derivative liabilities		(516)
Changes in operating assets and liabilities:
Accounts receivable	(21)	(2)
Prepaid expenses and other current assets	(244)	(291)
Other assets	(284)	(13)
Accounts payable	663	528
Accrued liabilities	(1,072)	(1,459)
Net cash used in operating activities	(4,035)	(3,937)
Cash flows from investing activities:
Additions to property, plant and equipment and water programs	(165)	(502)
Net cash used in investing activities	(165)	(502)
Cash flows from financing activities:
Net proceeds from issuance of stock	7,891
Principal payments on long-term debt	(14)	(14)
Net cash provided by (used in) financing activities	7,877	(14)
Net decrease in cash, cash equivalents and restricted cash	3,677	(4,453)
Cash, cash equivalents and restricted cash, beginning of period	12,691	13,163
Cash, cash equivalents and restricted cash, end of period	$ 16,368	$ 8,710