Income taxes - Net long-term deferred tax liability (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Research & development tax credits	$ 0	$ 58,069
Loss carry forward	130,911	443,076
Accrued compensation	146,057	82,503
Operating lease liabilities	501,397	412,840
Capitalized research expenditures	326,178	0
Other	29,094	0
Valuation allowances	0	(29,036)
Deferred tax assets	1,133,637	967,452
Deferred tax liabilities:
Property and equipment	325,473	293,195
Intangible assets	847,450	821,723
Operating lease right-of-use assets	491,494	412,840
Deferred Tax Liabilities, Gross	1,664,417	1,527,758
Net deferred tax liability	530,780	560,306
Discontinued Operations.
Deferred tax assets:
Operating loss carryforwards - Mexico	5,844,847	5,378,177
Valuation allowances	(15,678,994)	(11,816,716)
Land basis difference - Mexico	2,818,663	2,163,681
Start-up costs - Mexico	7,015,484	4,274,858
Deferred tax assets	$ 0	$ 0