Note 7 - Accounts Payable and Accrued Expenses - Summary of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts payable	$ 350	$ 315
Accrued payroll	184	156
Accrued interest	25	42
Total	559	513
Corporate, Non-Segment [Member]
Accounts payable	156	125
Accrued payroll	37	23
Accrued interest	25	42
Total
Operating Segments [Member] | Odor-No-More [Member]
Accounts payable	72	73
Accrued payroll	53	42
Accrued interest	0	0
Total
Operating Segments [Member] | BLEST [Member]
Accounts payable	73	56
Accrued payroll	94	91
Accrued interest	0	0
Total
Operating Segments [Member] | BioLargo Water [Member]
Accounts payable	96	103
Accrued payroll	0	0
Accrued interest	0	0
Total
Consolidation, Eliminations [Member]
Accounts payable	(47)	(42)
Accrued payroll	0	0
Accrued interest	0	0
Total