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

12 Months Ended

Dec. 31, 2021

Notes Tables

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

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	)

For the year ended December 31, 2020	Air Pollution Control Segment			FUEL CHEM Segment			Other			Total
Revenues from external customers	$	8,557		$	13,993		$	—		$	22,550
Cost of sales		(4,583	)		(7,329	)		—			(11,912	)
Gross margin		3,974			6,664			—			10,638
Selling, general and administrative		—			—			(13,600	)		(13,600	)
Research and development		—			—			(1,177	)		(1,177	)
Intangible assets abandonment		—			—			(197	)		(197	)
Operating income (loss) from continuing operations	$	3,974		$	6,664		$	(14,974	)	$	(4,336	)

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

For the years ended December 31,	2021		2020
Revenues:
United States	$	19,515	$	18,622
Foreign		4,746		3,928
	$	24,261	$	22,550

As of December 31,	2021		2020
Assets:
United States	$	46,271	$	24,524
Foreign		3,703		5,564
	$	49,974	$	30,088