Significant accounting policies (Details 1)	12 Months Ended
	Mar. 31, 2022
Factory and administrative buildings [Member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	20 years
Factory and administrative buildings [Member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	50 years
Ancillary structures [Member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	3 years
Ancillary structures [Member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	15 years
Plant and equipment [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	3 years
Plant and equipment [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	15 years
Furniture, fixtures and office equipment [Member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	3 years
Furniture, fixtures and office equipment [Member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	10 years
Vehicles [Member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	4 years
Vehicles [Member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Useful life measured as period of time, property, plant and equipment	5 years