Biomass residue characterization for their potential application as biofuels

A detailed understanding of chemical composition and thermal degradation behavior is very important for a biomass before processing it into a pyrolysis or gasification unit for energy production. In the present work, the physico- and thermo-chemical characterization of four different types of walnut shells (PSW, TSW, MSW and HSW) is carried out to evaluate their application as furnace oil. The thermal degradation behavior during the thermal decomposition of different walnut shells (WS) samples is studied using thermogravimetric analysis at three different heating rates (5, 10 and 15 °C min−1). It is observed that the complete moisture removal is below 152 °C, and the degradation of lignocellulosic biomass is occurred between ≈ 250 to ≈ 400 °C in the oxidizing atmosphere. For all different WS samples, the heating values are observed in the range of 13.8–18.4 MJ kg−1, which is comparable to the wood waste and lignite coal. The cellulose, hemicellulose, lignin and extractives in walnut shell are found to vary from 32.3 to 34.5, 21 to 27, 39 to 43 and 1.4 to 1.7%, respectively. The functional characterization of different WS is carried out using FTIR, and the most prominent FTIR band peak has been found at wave numbers of 3400, 2931, 1420 and 1050 cm−1, which is due to the stretching vibrations of –OH, CH–, aromatic C=C, and aliphatic ether and alcohol groups, respectively. Scanning electron microscopy analysis indicated the rough texture and heterogeneous structures of biomass. Further, the X-ray diffraction analysis showed the crystalline structure, which is due to the presence of cellulose. Therefore, it can be concluded that the walnut shell is a potential candidate for energy generation through thermo-chemical conversion.