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Summary of significant accounting policies (Tables)
12 Months Ended
Dec. 31, 2021
Summary of significant accounting policies  
Schedule of estimated useful lives for significant property and equipment

Buildings

    

20 years

Machinery and equipment

5 - 10 years

Transportation equipment

 

4 - 5 years

Office equipment

 

4 - 5 years

Electronic equipment

 

3 - 5 years

Schedule of estimated useful lives of intangible assets

    

Estimated Useful Life

Licenses and permits

Indefinite

Software

 

5 - 10 years

Land use right

 

50 years

Patents

 

10 years

Schedule of currency exchange rates that were used in creating the consolidated financial statements

    

December 31, 2021

    

December 31, 2020

    

December 31, 2019

US$: RMB exchange rate

Period End

    

$

0.1569

Period End

    

$

0.1533

    

Period End

    

$

0.1436

 

Average

$

0.1550

 

Average

$

0.1448

 

Average

$

0.1448