Note 2 - Significant Accounting Policies and Basis of Presentation (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022
Other Assets, Current	$ 8,675	$ 11,014
Inventory, Net	$ 20,643	$ 25,383
Environmental Assets [Member]
Property, Plant and Equipment, Useful Life (Year)	27 years
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Chemicals [Member]
Number Of Major Customers	0	0	0
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Biodiesel [Member]
Number Of Major Customers	2
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Biodiesel [Member] | Two Customers [Member]
Concentration Risk, Percentage	25.00%	35.00%	27.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Biodiesel [Member] | Two Customers [Member]
Concentration Risk, Percentage	13.00%	0.20%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Chemicals [Member]
Number Of Major Customers	1
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Chemicals [Member] | Chemical Customer 1 [Member]
Concentration Risk, Percentage	20.00%
Revision of Prior Period, Change in Accounting Principle, Adjustment [Member] | Change in Accounting Principle for Supplies and Parts [Member]
Other Assets, Current	$ 7,733	$ 7,595
Inventory, Net	$ 7,733	$ 7,595