<
em>
Agave<
/em>
has recently shown its potential as a bioenergy feedstock with promising features such as higher biomass productivity than leading bioenergy feedstock while at the same time being drought-resistant with low water requirements and high sugar to ethanol conversion using ionic liquid (IL) pretreatment. Here, IL pretreatment was studied to develop the first direct side-by-side comparative recalcitrance assessment of the agro-industrial residues from five Agave species [<
em>
Agave americana<
/em>
(AME), <
em>
A. angustifolia<
/em>
(ANG), <
em>
A. fourcroydes<
/em>
(FOU), <
em>
A. salmiana<
/em>
(SAL), and <
em>
A. tequilana<
/em>
(TEQ)] using compositional analysis, X-ray diffraction, and the lignin syringyl/guaiacyl subunit ratio (S/G) by pyrolysis molecular beam mass spectrometry (PyMBMS). Prominent calcium oxalate peaks were found only in unpretreated AME, SAL, and TEQ. The S/G ratios of all five unpretreated <
em>
Agave<
/em>
species were between 1.27 and 1.57 while the IL-pretreated samples were from 1.39 to 1.72. The highest overall sugar production was obtained with IL-pretreated FOU with 492 mg glucose/g biomass and 157 mg xylose/g biomass at 120�C and 3 h using 1-ethyl-3-methylimidazolium acetate ([C<
sub>
2<
/sub>
C<
sub>
1<
/sub>
Im][OAc]). An estimated theoretical ethanol yield from the studied agro-industrial residues from the five <
em>
Agave<
/em>
species was in the range of 1060 to 5800 L ethanol/ha/year. These comparison results demonstrate the potential of the <
em>
Agave<
/em>
spp. as a suitable biofuel feedstock which can be employed within a biorefinery scheme.