Note 1 - Nature of Business, Financial Condition, Basis of Presentation and Reverse Stock Split (Details Textual)			1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 03, 2018 shares	Jun. 01, 2018	Apr. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	May 30, 2018 $ / shares	Feb. 28, 2018 USD ($)	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Net Income (Loss) Attributable to Parent, Total				$ (11,492,000)	$ (10,158,000)	$ (13,994,000)	$ (16,091,000)
Retained Earnings (Accumulated Deficit), Ending Balance				(415,344,000)		(415,344,000)				$ (401,350,000)
Cash and Cash Equivalents, at Carrying Value, Ending Balance				$ 27,030,000		27,030,000				$ 11,553,000
Proceeds from At-the-Market Offering Program						14,900,000
Proceeds from Issuance of Common Stock						$ 22,415,000	11,044,000
Common Stock, Par or Stated Value Per Share | $ / shares				$ 0.01		$ 0.01		$ 0.01		$ 0.01
Operating Leases, Future Minimum Payments Due, Total				$ 2,322,000		$ 2,322,000
Increase (Decrease) Restricted Cash Held as Collateral			$ (2,600,000)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Ending Balance				$ 27,030,000	$ 16,303,000	$ 27,030,000	$ 16,303,000			$ 11,553,000	$ 30,499,000
Previously Reported [Member] | Accounting Standards Update 2016-18 [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Ending Balance											$ 27,900,000
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio		20
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Ethanol [Member]
Concentration Risk, Percentage				69.00%	75.00%	71.00%	77.00%
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
Increase (Decrease) in At-the-Market Offering of Stock				$ 84,900,000
Stock Issued During Period, Shares, New Issues | shares	14,500,000			6,281,409		6,286,617
Proceeds from Issuance of Common Stock				$ 37.40		$ 37,400,000
Payments of Stock Issuance Costs				200,000		400,000
At-the-market Offering [Member] | Sales Agent [Member]
Payments of Stock Issuance Costs				$ 900,000		$ 900,000