Revenue (Tables)

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table presents the timing of our revenue recognition:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2019		2018		2019		2018
Products transferred at a point in time	$	5,261	$	5,868	$	15,828	$	15,192
Products and services transferred over time	1,191		10,202		9,727		25,516
Total Revenues	$	6,452	$	16,070	$	25,555	$	40,708

The following table presents our revenues disaggregated by product technology:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2019		2018		2019		2018
Air Pollution Control
Technology solutions	$	1,191	$	10,202	$	9,727	$	25,516
Spare parts	299		334		832		863
Ancillary revenue	326		346		1,849		1,493
Total Air Pollution Control Technology revenues	1,816		10,882		12,408		27,872
FUEL CHEM
FUEL CHEM technology solutions	4,636		5,188		13,147		12,836
Total Revenues	$	6,452	$	16,070	$	25,555	$	40,708

Revenue Disaggregated by Geography

The following table presents our revenues disaggregated by geography, based on the billing addresses of our customers:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2019		2018		2019		2018
United States	$	5,727	$	11,629	$	22,104	$	30,701
Foreign Revenues
South America	282		278		474		904
Europe	283		1,907		1,568		4,935
Asia	160		2,256		1,409		4,168
Total Foreign Revenues	725		4,441		3,451		10,007
Total Revenues	$	6,452	$	16,070	$	25,555	$	40,708

Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]

The components of accounts receivable are as follows:

	As of
	September 30, 2019			December 31, 2018
Trade receivables	$	7,563		$	14,261
Unbilled receivables	1,589			5,540
Insurance proceeds receivable (Note 14)	1,991			—
Other short-term receivables	156			9
Allowance for doubtful accounts	(1,175		)	(1,411		)
Total accounts receivable	$	10,124		$	18,399