Physicochemical characterization of Malaysian crop and agro-industrial biomass residues as renewable energy resources

Abstract

Detailed investigation on the physicochemical characterization of Malaysian crop and agro-industrial biomass residues has been carried out to identify promising feedstock for thermochemical and biochemical energy yield. This study covered a wide range of biomass residues including oil palm frond (OPF), oil palm trunk (OPT), empty fruit bunches (EFB), palm kernel shell (PKS), rice husk (RH), rice straw (RS) and kenaf biomass (K). From the detailed characterization studies based on proximate composition, CHNS/O analysis, calorific value and lignocellulosic content determination, physicochemical properties of biomass residues were correlated with their potential for bioenergy generation. In addition, various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG) and X-ray fluorescence spectroscopy (XRF) were used to study various microscopic properties of biomass residues such as functional groups, crystallographic structure, thermal degradation and mineralogical composition, respectively. Results showed that in terms of volatile matter, the order followed was; EFB (83.42%) ˃ K (82.70%) ˃ OPT (81.46%) ˃ OPF (76.98%) ˃ RS (76.42%) ˃ PKS (69.66%) ˃ RH (66.65%). Proximate analysis revealed that RH has the highest ash content (18.82%). Notably, minimum undesirable ash material was generated by K (5.73%), EFB (6.56%) and OPT (7.71%) containing high fractions of catalytic species. PKS presented maximum thermochemical potential with higher heating value of 17.32 MJ/kg followed by K (16.66 MJ/kg), OPT (16.34 MJ/kg), RS (16.15 MJ/kg), EFB (16.07 MJ/kg), OPF (14.49 MJ/kg) and RH (14.37 MJ/kg). Due to highest apparent density and maximum content of fixed carbon as well as lignin, PKS can be an interesting energy resource in thermochemical processes. Compositional analysis revealed that OPF, OPT and K were rich in polysaccharide content with much less quantity of lignin. Based on XRD measurements, it was found that EFB and K would be more susceptible to enzymatic digestion due to lower crystallinity index (CrI) compared to other residues. We believe that these investigations could decisively contribute to a better understanding of the influence of different factors related to lignocellulosic biomass feedstock on the efficiency of conversion and biofuel potential.