UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)
Cash flows used in operating activities:
Net loss	$ (13,180)	$ (13,889)	$ (33,930)	$ (27,798)
Adjustments to reconcile net loss for the period to net cash used in operating activities:
Non-cash interest expense – Note 9			12,396	6,000
Asset retirement obligation adjustments – Note 12			3,963	0
Stock-based compensation – Note 15			1,479	1,560
Depreciation and amortization – Notes 2 and 5			1,183	1,429
Accretion – Note 12	295	186	527	372
Unrealized loss on securities	490		490	0
Loss (gain) on sale of equipment, net of commissions	0	(85)	131	(85)
Write-down of supplies inventories	0	0	12	0
Gain on fair value adjustment for warrant liabilities	(1)	(59)	(7)	(181)
Gain on settlement of accrued liability	0	(1,151)	0	(1,151)
Gain on non-refundable deposit – Note 10	(109)	0	(1,550)	0
Gain on sale of patents	(3,641)	0	(3,641)	0
Changes in operating assets and liabilities:
Accounts payable and accrued expenses			416	(2,426)
Interest receivable			307	(80)
Contract liabilities – Note 10			300	100
Supplies inventories, net – Note 4			52	13
Other receivable			0	2,771
Prepaids – Note 3			(316)	(1,763)
Other assets, non-current			(319)	0
Other liabilities – Note 11			(1,824)	(1,195)
Net cash used in operating activities			(20,331)	(22,434)
Cash flows provided by (used in) investing activities:
Proceeds from patent sale			1,447	0
Proceeds from sale of equipment			270	103
Additions to property, plant, and equipment			(449)	(726)
Net cash provided by (used in) by investing activities			1,268	(623)
Cash flows provided by (used in) financing activities:
Proceeds from issuance of common stock, net of issuance costs – Note 14			10,053	0
Principal payments on notes payable			(62)	(63)
Principal payments on debt – Note 9			(37,995)	(1,100)
Net cash used in financing activities			(28,004)	(1,163)
Net decrease in cash, cash equivalents, and restricted cash			(47,067)	(24,220)
Cash, cash equivalents, and restricted cash, beginning of period			132,550	175,966
Cash, cash equivalents, and restricted cash, end of period	85,483	151,746	85,483	151,746
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	58,548	117,064	58,548	117,064
Restricted cash	26,935	34,682	26,935	34,682
Total cash, cash equivalents, and restricted cash	$ 85,483	$ 151,746	$ 85,483	$ 151,746