有关纸类回收的问题， 为什么报纸和纸板不能混合回收

小弟无奈写论文，原问题是这样的Why does the City request that certain types of materials are to be separated? (example Cardboard from Newspapers)? What happens if they are mixed and given to a company to re-use such as mixing newspaper and cardboard for re-use in the manufacture of office paper?What are the chemical, organic, inorganic properties that affect (or prevent) the manufacturer to re-use the mix for office paper, for example.
What are the chemical, organic, inorganic properties that affect (or prevent) the manufacturer to re-use the mix for office paper, for example

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