Pyrolysis of hull-enriched byproducts from the scarification of hulled barley (Hordeum vulgare L.)

Characterization of biomass devolatilization products can provide important information for understanding the synergy between its decomposition pathways and subsequent thermochemical energy conversion processes such as direct combustion, gasification or production of intermediate pyrolysis products including bio-oils. The proposed use of hulled barley (Hordeum vulgare L.), as feedstock for ethanol production in the corn deficit Eastern and Northwestern United States would generate significant quantities of residual hulls but can also be a potential source of thermal energy capable of improving the economies of the process. In this study, the initial thermal degradation of hull-enriched fractions from three barley varieties including slow and fast pyrolysis was characterized via thermolysis. The study employed a wide range of pyrolysis experiments including thermogravimetry (TGA), pyrolysis-gas chromatography with mass-spectral analysis (PY-GC-MS) and hot phase environmental scanning electro microscopy (ESEM). All experiments were performed within the high temperature range of 600-1050 °C. The apparent first order rates of the early stages of the devolatilization process in the TGA showed no significant differences in the estimated activation energy of the varieties tested. The pyrolysis yields grouped under condensable gas (bio-oil), non-condensable gas (synthetic gas), and char were more temperature dependent than variety dependent. Similar results were found with the fractional composition of the synthesis gas. The hot stage environmental SEM revealed interesting gas evolution patterns and char microstructure development in real time during thermal degradation of the biomass. The information presented is useful for the understanding of the thermochemical conversion of barley hull-containing fractions and offers design implications regarding unit operations either for stand-alone biomass energy conversion systems or for co-located systems in an integrated ethanol production facility.