Long and short-term capital leases (Tables)

12 Months Ended

Dec. 31, 2014

Long and short-term capital leases

Schedule of long and short-term capital leases

	December 31,
	2014			2013
Capital leases to various lessors secured by financed equipment with interest rates ranging from 4.67% to 14.51%. Principal and interest are payable monthly through May 2018	$	816,718		$	949,596
Total long and short-term portions of capital leases		816,718			949,596
Less: short-term portion capital leases		(458,812	)		(466,010	)
Long-term portion of capital leases	$	357,906		$	483,586

Schedule of interest expense related to capital leases

	Year ended December 31,
	2014		2013		2012
Capital leases	$	61,591	$	60,106	$	55,699