They're not leaving it in the soil. The benzene is extracted as a useful byproduct.

Yes, they are leaving it in the soil. Prove me wrong with data. It says nothing at all about extracting the waste benzene they created from the soil, neither in the linked article nor in the complete paper, which i did read. The paper specifically describes an in-situ process. If it were economically beneficial to extract benzene from contaminated soil for industrial use, we would already be doing that with the tens of thousands of existing benzene contaminated sites, not creating more of them.