The single ionization and dissociation of ethanol molecules induced by low-energy electrons (
E
0
=
90
eV
) are investigated using multiparticle coincident momentum spectroscopy. By detecting two outgoing electrons (
e
1
and
e
2
) and one fragment ion in coincidence, we obtain the energy deposition (
E
0
−
E
1
−
E
2
) during electron ionization of the molecule, i.e., the binding energy spectra, for production of the different ionic fragments C2H5OH+, C2H4OH+, COH+, and H3O+. These data allow us to study the ionization channels for different ionic products. In particular, we focus on H3O+ as a product of double hydrogen migration. It is found that this channel mainly originates from the ionization of outer-valance orbitals (3a
″
,10a
′
, 2a
″
, 9a
′
, 8a
′
, 1a
″
, and 7a
′
). Additionally, there are minor contributions from the inner-valence orbitals such as 6a
′
, 5a
′
, and 4a
′
. Quantum chemistry calculations show two fragmentation pathways: concerted and sequential processes for formation of H3O+.