Property, plant and equipment and construction in progress (Details) - USD ($)	Dec. 31, 2024	Dec. 31, 2023
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	$ 141,260,376	$ 145,171,425
Less accumulated depreciation	88,828,094	89,288,904
Property, plant and equipment, net	52,432,282	55,882,521
Construction in progress	5,143,717	495,471
Land
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	6,307,089	6,488,400
Buildings
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	26,033,866	26,044,551
Plant and equipment
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	61,089,877	66,000,977
Distribution system
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	40,402,691	39,546,175
Office furniture, fixtures and equipment
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	3,277,313	3,338,760
Vehicles
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	3,830,539	3,433,561
Leasehold improvements
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	306,545	306,545
Lab equipment
Property, plant and equipment and construction in progress
Property, plant and equipment, gross	$ 12,456	$ 12,456