Property, plant and equipment, net (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 971,372,712		$ 958,565,093
Less accumulated depreciation	(200,959,201)		(182,623,813)
Property, plant and equipment, net	770,413,511		775,941,280
Capitalized interest expense	387,324	$ 643,788
Machinery, equipment and furniture [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	587,775,600		580,735,482
Motor vehicles [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	2,810,727		2,658,487
Workshops and buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	160,475,642		157,976,839
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 220,310,743		$ 217,194,285

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of interest capitalized during the period.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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