Question

Where does industrial waste come from?

Answer 1

See the example in the explanation

Explanation:

It is the unwanted by-product of industrial processes. It is not unusual for this by-product to have no reusable properties.

One example that springs to mind is the recycling of gold from electronic components and circuit boards. The gold it self has value that warrants the cost of using the chemicals necessary to retrieve the gold. However, after the process is complete the chemicals would have undergone change. I have no idea what the chemistry involved is but there is bound to be at least one by-product that would need specialist disposal due to the nature of the chemical type.