Business Segment Information - Segment Operating Results (Details) $ in Thousands	2 Months Ended	3 Months Ended			9 Months Ended
	Mar. 03, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 segment	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues:
Earnings (loss) from equity method investments		$ 10,735		$ (41)	$ 30,066	$ 5,133
Consulting services		171		665	492	1,349
Royalties		2,064		3,273	3,922	7,767
Equipment sales		14,869		12,088	44,788	47,439
Chemicals		670		132	1,717	749
Total reported revenues		15,710		12,885	46,997	49,537
Segment reporting operating income (loss)
Total segment operating income (loss)		(2,913)		(9,989)	(10,870)	(34,665)
Gain on sale of equity method investment		0		0	2,078	0
453A interest		889		1,136	2,034	3,408
RCM6 note payable, related party		0		628	263	1,842
Other Nonoperating Income (Expense)
Segment reporting operating income (loss)
Gain on contract termination		900
RMC6, LLC (RCM6)
Revenues:
Earnings (loss) from equity method investments	$ (557)	0		(1,399)	(557)	(3,127)
Segment reporting operating income (loss)
Gain on sale of equity method investment		2,100
Refined Coal | RMC6, LLC (RCM6)
Segment reporting operating income (loss)
Gain on sale of equity method investment					2,100
453A interest		900		1,100	2,000	3,400
RCM6 note payable, related party		0		600	300	1,800
Operating Segments
Revenues:
Total reported revenues		28,509		16,117	80,985	62,437
Segment reporting operating income (loss)
Total segment operating income (loss)		14,869		(2,007)	43,630	(840)
Operating Segments | Refined Coal
Revenues:
Earnings (loss) from equity method investments		10,735		(41)	30,066	5,133
Consulting services		0		0	0	55
Royalties		2,064		3,273	3,922	7,767
Total reported revenues		12,799		3,232	33,988	12,955
Segment reporting operating income (loss)
Total segment operating income (loss)		11,913		1,390	33,974	7,350
Operating Segments | Emissions Control
Revenues:
Consulting services		171		665	492	1,294
Equipment sales		14,869		12,088	44,788	47,439
Chemicals		670		132	1,717	749
Total reported revenues		15,710		12,885	46,997	49,482
Segment reporting operating income (loss)
Total segment operating income (loss)		2,956		(3,397)	9,656	(8,190)
Intersegment Eliminations | Refined Coal
Revenues:
Earnings (loss) from equity method investments		(10,735)		41	(30,066)	(5,133)
Royalties		(2,064)		(3,273)	(3,922)	(7,767)
Total reported revenues		$ (12,799)		$ (3,232)	$ (33,988)	$ (12,900)