Long and short-term capital leases (Tables)

12 Months Ended

Dec. 31, 2016

Long and short-term capital leases

Schedule of long and short-term capital leases

	December 31,
	2016		2015
Capital leases to various lessors secured by financed equipment with interest rates ranging from 4.15% to 13.45%. Principal and interest are payable monthly through May 2021	$	268,843	$	487,111
Total long and short-term portions of capital leases		268,843		487,111
Less: short-term portion capital leases		(166,966)		(290,911)
Long-term portion of capital leases	$	101,877	$	196,200

Schedule of interest expense related to capital leases

	Year ended December 31,
	2016		2015		2014
Capital leases	$	28,668	$	46,958	$	61,591