Note 3 - Revenues from Contracts with Customers and Other Revenues - Disaggregated Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer, Including Assessed Tax	$ 24,453	$ 32,863
Other revenues	34
Total revenues	24,487	32,863
Transferred at Point in Time [Member]
Revenue from Contract with Customer, Including Assessed Tax	24,453	32,838
Other revenues
Total revenues	24,453	32,838
Transferred over Time [Member]
Revenue from Contract with Customer, Including Assessed Tax		25
Other revenues	34
Total revenues	34	25
Ethanol Sales and Related Products [Member]
Revenue from Contract with Customer, Including Assessed Tax	22,115	31,641
Other revenues
Total revenues	22,115	31,641
Hydrocarbon [Member]
Revenue from Contract with Customer, Including Assessed Tax	2,338	1,197
Other revenues
Total revenues	2,338	1,197
Grant and Other [Member]
Revenue from Contract with Customer, Including Assessed Tax		25
Other revenues	34
Total revenues	$ 34	$ 25