Note 6 - Property, Plant and Equipment (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment, Gross, Ending Balance	$ 164,797	$ 125,525
Construction in Progress [Member]
Property, Plant and Equipment, Gross, Ending Balance	51,033	13,132
Construction in Progress [Member] | Gevo [Member]
Property, Plant and Equipment, Gross, Ending Balance	600	0
Construction in Progress [Member] | Agri-Energy [Member]
Property, Plant and Equipment, Gross, Ending Balance	8,400	8,600
Construction in Progress [Member] | Renewable Natural Gas [Member]
Property, Plant and Equipment, Gross, Ending Balance	36,000	4,500
Construction in Progress [Member] | Net-Zero [Member]
Property, Plant and Equipment, Gross, Ending Balance	$ 6,000	$ 0