Note 10 - Business Segment and Geographic Financial Data (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

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

Three months ended September 30, 2020	Air Pollution Control Segment		FUEL CHEM Segment			Other			Total
Revenues from external customers	$	2,886	$	5,269		$	—		$	8,155
Cost of sales		304		(2,553	)		—			(2,249	)
Gross margin		3,190		2,716			—			5,906
Selling, general and administrative		—		—			(3,184	)		(3,184	)
Research and development		—		—			(285	)		(285	)
Operating income (loss) from continuing operations	$	3,190	$	2,716		$	(3,469	)	$	2,437

Three months ended September 30, 2019	Air Pollution Control Segment			FUEL CHEM Segment			Other			Total
Revenues from external customers	$	1,816		$	4,636		$	—		$	6,452
Cost of sales		(1,197	)		(2,366	)		—			(3,563	)
Gross margin		619			2,270			—			2,889
Selling, general and administrative		—			—			(3,822	)		(3,822	)
Restructuring Charge		—			—			—			—
Research and development		—			—			(352	)		(352	)
Intangible assets abandonment		—			—			(76	)		(76	)
Operating income (loss) from continuing operations	$	619		$	2,270		$	(4,250	)	$	(1,361	)

Nine months ended September 30, 2020	Air Pollution Control Segment			FUEL CHEM Segment			Other			Total
Revenues from external customers	$	6,019		$	10,315		$	—		$	16,334
Cost of sales		(2,782	)		(5,517	)		—			(8,299	)
Gross margin		3,237			4,798			—			8,035
Selling, general and administrative		—			—			(9,825	)		(9,825	)
Research and development		—			—			(880	)		(880	)
Operating income (loss) from continuing operations	$	3,237		$	4,798		$	(10,705	)	$	(2,670	)

Nine months ended September 30, 2019	Air Pollution Control Segment			FUEL CHEM Segment			Other			Total
Revenues from external customers	$	12,408		$	13,147		$	—		$	25,555
Cost of sales		(8,061	)		(6,693	)		—			(14,754	)
Gross margin		4,347			6,454			—			10,801
Selling, general and administrative		—			—			(12,735	)		(12,735	)
Restructuring Charge		—			—			(625	)		(625	)
Research and development		—			—			(823	)		(823	)
Intangible assets abandonment		—			—			(127	)		(127	)
Operating income (loss) from continuing operations	$	4,347		$	6,454		$	(14,310	)	$	(3,509	)

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Revenues:
United States	$	6,473	$	5,727	$	12,880	$	22,104
Foreign		1,682		725		3,454		3,451
	$	8,155	$	6,452	$	16,334	$	25,555

	September 30, 2020		December 31, 2019
Assets:
United States	$	25,008	$	23,460
Foreign		6,517		8,146
	$	31,525	$	31,606