Prepayments and other receivables (Details) - USD ($)		Dec. 31, 2018	Dec. 31, 2017
Value-added tax ("VAT") prepayment		$ 8,227,478	$ 3,132,236
Other receivables from third parties		1,109,527	444,263
Payroll deposit		365,059	0
Compensation receivable for land occupation		0	486,019
Prepaid expense		755,725	692,028
Prepaid Expense and Other Receivables, Gross, Current		10,457,789	4,754,546
Less: allowance for doubtful accounts	[1]	0	486,019
Prepaid Expense and Other Assets, Current		$ 10,457,789	$ 4,268,527

[1] The Company collected the receivable and reversed the allowance for doubtful accounts of $476,618 for the year ended December 31, 2018.