Annual report pursuant to Section 13 and 15(d)

Note 13 - Stockholders' Equity - Warrant Assumptions (Details)

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Note 13 - Stockholders' Equity - Warrant Assumptions (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2020
Feb. 26, 2019
Jan. 31, 2019
Exercise price (in dollars per share) $ 1.90    
Veolia Warrants 1 [Member]      
Warrant shares issued (in shares) 2,000,000 2,000,000  
Market price (in dollars per share) $ 3.02    
Exercise price (in dollars per share) $ 5.00 $ 5.00  
Term (years) (Year) 10 years    
Risk free interest rate 2.64%    
Expected stock volatility 81.50%    
Dividend yield 0.00%    
Per share FV of warrant (in dollars per share) $ 2.35    
FV of warrant $ 4,699    
Veolia Warrants 2 [Member]      
Warrant shares issued (in shares) 2,000,000 2,000,000  
Market price (in dollars per share) $ 3.02    
Exercise price (in dollars per share) $ 7.00 $ 7.00  
Term (years) (Year) 10 years    
Risk free interest rate 2.64%    
Expected stock volatility 81.50%    
Dividend yield 0.00%    
Per share FV of warrant (in dollars per share) $ 2.24    
FV of warrant $ 4,474    
January 2019 Underwriter Warrants [Member]      
Warrant shares issued (in shares) 103,500   103,500
Market price (in dollars per share) $ 2.16    
Exercise price (in dollars per share) $ 1.90   $ 1.90
Term (years) (Year) 5 years    
Risk free interest rate 2.57%    
Expected stock volatility 81.00%    
Dividend yield 0.00%    
Per share FV of warrant (in dollars per share) $ 1.47    
FV of warrant $ 152