Usage of marginal lands to grow perennial grass for biomass feedstocks is a promising option to meet the bioenergy demand in India. In this context, the present work investigated the potential utility of two perennial grass species Cenchnis ciliaris (L) and Pennisetum pedicellatum (Tan.) to be a new promising energy source for bioenergy. This study entails a detailed characterization of biomass feedstocks using proximate and ultimate analysis, and lignocellulosic fractions and thermogravimetric behaviour using TG-FTIR and Py-GCIMS spectrophotometry to evaluate their potential as an alternate green fuel to fossil fuels by measuring their thermochemical conversion functioning. Property analysis of perennial grass species showed a significant difference in moisture content (7.2-8.5%), volatile matters (80.5-82.4%), fixed carbon (11.3-18.9%), HHV (15-17.8 Mj/kg) and LHV (14.3-16.5 Mj/kg), which is very promising for bioenergy generation. Lignocellulosic fractions of biomass feedstocks are comparable to the previous studied biomass species including switchgrass and elephant grass. The individual decomposition experiments indicated that biomass feedstocks possess higher thermochemical reactivity and shorter devolatilization time. According to Py-GC/MS study, carbonyl compounds including aldehyde and ketones are the major volatile products, in addition to furans, benzenes, phenols, acids, and others. The TGR1R results showed that main gaseous products evolved during devolatilization are CO, CO2, CH4, and H2O. All of the results and findings would help in characterizing the biomass as potential bioenergy feedstocks compatible with other biomass currently in use as supplementary fuel for power generation. (C) 2018 Elsevier Ltd. All rights reserved.