Note 1 - Nature of Business, Financial Condition, Basis of Presentation and Reverse Stock Split (Details Textual)	1 Months Ended	3 Months Ended
	Apr. 30, 2017 USD ($)	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 USD ($)	Feb. 28, 2018 USD ($)	Dec. 31, 2017 USD ($)
Net Income (Loss) Attributable to Parent, Total		$ (2,502,000)	$ (5,934,000)
Retained Earnings (Accumulated Deficit), Ending Balance		(403,852,000)			$ (401,350,000)
Cash and Cash Equivalents, at Carrying Value, Ending Balance		7,029,000	20,393,000		$ 11,553,000
Proceeds from Issuance of Common Stock		57,000	$ 11,044,000
Operating Leases, Future Minimum Payments Due, Total		$ 2,685,000
Increase (Decrease) Restricted Cash Held as Collateral	$ (2,600,000)
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Ethanol [Member]
Concentration Risk, Percentage		74.00%	80.00%
Number of Customers		1
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Customer One [Member] | Ethanol [Member]
Concentration Risk, Percentage		100.00%
At-the-market Offering [Member]
Offering of Stock, Authorized Amount				$ 5,000,000
Stock Issued During Period, Shares, New Issues | shares		104,138
Proceeds from Issuance of Common Stock		$ 100,000
Payments of Stock Issuance Costs		200,000
Offering of Stock, Remaining Amount		4,900,000
At-the-market Offering [Member] | Sales Agent [Member]
Payments of Stock Issuance Costs		$ 1,000