How do domestic garbage disposal companies make money?

Waste composting sites can sell fertilizers, recycling plants can buy valuable wastes, and landfill sites can use biogas to generate electricity. In addition to power generation, the garbage incineration plant also has the garbage disposal fee of zf, which is about 100 ~ 200 yuan per ton. In addition, the state also gives preferential tax treatment to garbage disposal enterprises, so there is no problem with profits.