Business Segment, Geographic and Quarterly Financial Data - Reporting Segment Net Sales and Gross Margin (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from external customers	$ 73,664,000	$ 79,017,000	$ 109,338,000
Cost of sales	(45,107,000)	(43,889,000)	(62,521,000)
Gross margin	28,557,000	35,128,000	46,817,000
Selling, general and administrative	(31,116,000)	(35,432,000)	(36,375,000)
Research and development	(4,273,000)	(1,459,000)	(2,442,000)
Intangible assets impairment	(1,425,000)	0	0
Goodwill impairment	0	(23,400,000)
Operating (loss) income	(8,257,000)	(25,163,000)	8,000,000
Air Pollution Control Segment
Revenues from external customers	43,485,000	42,031,000	72,552,000
Cost of sales	(30,612,000)	(26,586,000)	(45,138,000)
Gross margin	12,873,000	15,445,000	27,414,000
Selling, general and administrative	0	0	0
Research and development	0	0	0
Intangible assets impairment	(1,425,000)
Goodwill impairment		(23,400,000)
Operating (loss) income	11,448,000	(7,955,000)	27,414,000
FUEL CHEM Segment
Revenues from external customers	30,179,000	36,986,000	36,786,000
Cost of sales	(14,495,000)	(17,303,000)	(17,383,000)
Gross margin	15,684,000	19,683,000	19,403,000
Selling, general and administrative	0	0	0
Research and development	0	0	0
Intangible assets impairment	0
Goodwill impairment	0	0
Operating (loss) income	15,684,000	19,683,000	19,403,000
Fuel Conversion Segment
Revenues from external customers	0	0
Cost of sales	0	0
Gross margin	0	0
Selling, general and administrative	0	0
Research and development	(2,826,000)	(277,000)
Intangible assets impairment	0
Goodwill impairment		0
Operating (loss) income	(2,826,000)	(277,000)
Other
Revenues from external customers	0	0	0
Cost of sales	0	0	0
Gross margin	0	0	0
Selling, general and administrative	(31,116,000)	(35,432,000)	(36,375,000)
Research and development	(1,447,000)	(1,182,000)	(2,442,000)
Intangible assets impairment	0
Goodwill impairment		0
Operating (loss) income	$ (32,563,000)	$ (36,614,000)	$ (38,817,000)