Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued liabilities
Compensation and benefits	$ 3,669	$ 3,489
Professional fees	297	223
LNG fuel and transportation	2,283	2,788
Accrued interest	29	53
Contract liabilities	315	83
Other taxes payable	573	717
Other accrued liabilities	245	260
Total accrued liabilities	$ 7,411	$ 7,613