A system for extracting metals (e.g. precious metals or dangerous metals) from a substrate material such as sludge from a lake bed or sewage treatment facility includes processing the substrate material and metals by exposing the substrate material and metals to the plasma of an electric arc. Then, the exposed substrate material and metals are passed through an electrically charged collection grid in which the metals, now electrically charged, are attracted to the collection grid and hold to the collection grid and the substrate material exits the collection grid with less concentrations (or none) of the metals. In some embodiments, in addition to recovering the metals (e.g. precious metals, dangerous metals, etc.), a flammable gas is produced.