Note 3 - Revenue (Tables)

9 Months Ended

Sep. 30, 2024

Notes Tables

Disaggregation of Revenue [Table Text Block]

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
Air Pollution Control
Technology solutions	$	2,554	$	1,910	$	6,837	$	7,449
Spare parts		424		1,339		1,428		1,938
Ancillary revenue		246		462		1,226		1,305
Total Air Pollution Control technology revenues		3,224		3,711		9,491		10,692
FUEL CHEM
FUEL CHEM technology solutions		4,627		4,277		10,359		10,044
Total Revenues	$	7,851	$	7,988	$	19,850	$	20,736

Revenue from External Customers by Geographic Areas [Table Text Block]

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
United States	$	5,453	$	5,640	$	13,519	$	15,937
Foreign Revenues
Latin America		208		157		816		310
Europe		1,526		1,001		4,070		2,400
Asia		664		1,190		1,445		2,089
Total Foreign Revenues		2,398		2,348		6,331		4,799
Total Revenues	$	7,851	$	7,988	$	19,850	$	20,736

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
Products transferred at a point in time	$	5,297	$	6,078	$	13,013	$	13,287
Products and services transferred over time		2,554		1,910		6,837		7,449
Total Revenues	$	7,851	$	7,988	$	19,850	$	20,736

Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]

	As of
	September 30, 2024			December 31, 2023
Trade receivables	$	4,432		$	4,300
Unbilled receivables		2,839			2,285
Receivable for employee retention credit		1,677			—
Other short-term receivables		360			255
Allowance for credit losses		(106	)		(111	)
Total accounts receivable	$	9,202		$	6,729