Note 12 - Business Segment and Geographic Financial Data (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Schedule of Segment Reporting Information, by Segment [Table Text Block]

For the year ended December 31, 2022	Air Pollution Control Segment			FUEL CHEM Segment			Other			Total
Revenues from external customers	$	10,597		$	16,344		$	—		$	26,941
Cost of sales		(6,924	)		(8,374	)		—			(15,298	)
Gross margin		3,673			7,970			—			11,643
Selling, general and administrative		—			—			(12,275	)		(12,275	)
Research and development		—			—			(895	)		(895	)
Operating income (loss) from continuing operations	$	3,673		$	7,970		$	(13,170	)	$	(1,527	)

For the year ended December 31, 2021	Air Pollution Control Segment			FUEL CHEM Segment			Other			Total
Revenues from external customers	$	6,896		$	17,365		$	—		$	24,261
Cost of sales		(3,529	)		(8,834	)		—			(12,363	)
Gross margin		3,367			8,531			—			11,898
Selling, general and administrative		—			—			(12,055	)		(12,055	)
Research and development		—			—			(1,332	)		(1,332	)
Operating income (loss) from continuing operations	$	3,367		$	8,531		$	(13,387	)	$	(1,489	)

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]

For the years ended December 31,	2022		2021
Revenues:
United States	$	20,311	$	19,515
Foreign		6,630		4,746
	$	26,941	$	24,261

As of December 31,	2022		2021
Assets:
United States	$	47,007	$	46,271
Foreign		3,117		3,703
	$	50,124	$	49,974