To gain the highest theoretical amount of energy from an organic substrate, the substrate
needs to be completely oxidized to carbon dioxide with efficient transfer of electrons to the electrode.
Without the complete oxidation of the organic substrate, energy is lost from the system in the form of
unoxidized substrate. For example, studies found that Shewanella oneidensis that did not completely
oxidize the organic substrate lactate in a MFC, leaving electrons unutilized as waste products such as
acetate, had a columbic efficiency of about 56.2% .