Fermentation is an anaerobic process that does not use an electron transport chain.

Fermentation

A metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen.

Anaerobic Process

A metabolic process that occurs in the absence of oxygen, used by certain organisms to generate energy.

Electron Transport Chain

A series of complexes that transfer electrons from electron donors to electron acceptors via redox reactions, coupled with the transfer of protons across a membrane, to create a proton gradient that drives ATP synthesis.