Accounts receivable, net (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable, net.
Trade accounts receivable	$ 27,409,029	$ 21,422,782
Receivable from OC-BVI	40,877	62,171
Other accounts receivable	180,262	269,133
Accounts Receivable, Gross, Current	27,630,168	21,754,086
Allowance for doubtful accounts	(280,861)	(270,110)	$ (142,236)
Accounts receivable, net	$ 27,349,307	$ 21,483,976