Note 7 - Debt - Convertible Notes Payable (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	May 15, 2011
Debt Instrument, Interest Rate, Stated Percentage			10.00%
The 2008 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Note Conversion Price (in dollars per share)	$ 0.25
Warrant Exercise Price (in dollars per share)	$ 0.45
Term (Year)	1 year
The 2009 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Note Conversion Price (in dollars per share)	$ 0.08
Warrant Exercise Price (in dollars per share)	$ 0.30
Term (Year)	1 year	1 year
The June 2010 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	12.00%
Note Conversion Price (in dollars per share)	$ 0.08
Warrant Exercise Price (in dollars per share)	$ 0.30
Term (Year)	1 year
The November 2010 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Note Conversion Price (in dollars per share)	$ 0.06
Warrant Exercise Price (in dollars per share)	$ 0.30
Term (Year)	1 year	1 year
The May 2012 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Note Conversion Price (in dollars per share)	$ 0.10
Warrant Exercise Price (in dollars per share)	$ 0.35
Term (Year)	1 year 180 days	1 year 180 days
The February 2014 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Note Conversion Price (in dollars per share)	$ 0.10
Warrant Exercise Price (in dollars per share)
Term (Year)	1 year 180 days	1 year 180 days
The 2015 Offering [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Note Conversion Price (in dollars per share)	$ 0.10
Warrant Exercise Price (in dollars per share)	$ 0.15
Term (Year)	1 year 180 days	1 year 180 days

CleanTech Biofuels, Inc. 10-Q