Automobile manufacturing is changing, and so is sludge. In the era of traditional fuel vehicles, the coating, electroplating, and phosphating lines left behind HW21/HW22 hazardous waste sludge containing chromium, nickel, and copper; in the era of new energy, battery housings, electric drive components, stamping cleaning, and coating pretreatment superimposed more complex water-based sludge and mixed heavy metal sludge. Disposal unit price is high, billed per ton