Note 7 - Accounts Payable and Accrued Expenses - Summary of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accounts payable	$ 670	$ 717
Accrued payroll	194	198
Accrued interest	25	25
Total	889	940
Corporate, Non-Segment [Member]
Accounts payable	208	187
Accrued payroll	40	20
Accrued interest	25	25
Operating Segments [Member] | Odor-No-More [Member]
Accounts payable	417	486
Accrued payroll	85	58
Accrued interest	0	0
Operating Segments [Member] | BLEST [Member]
Accounts payable	5	7
Accrued payroll	69	120
Accrued interest	0	0
Operating Segments [Member] | BioLargo Water [Member]
Accounts payable	91	119
Accrued payroll	0	0
Accrued interest	0	0
Operating Segments [Member] | BioLargo Energy Technologies, Inc (BETI) [Member]
Accounts payable	31
Accrued payroll	0
Accrued interest	0
Consolidation, Eliminations [Member]
Accounts payable	(82)	(82)
Accrued payroll	0	0
Accrued interest	$ 0	$ 0