Abstract
Wheat straw was hydrothermally pretreated over a broad severity range (90–300 °C) to comparatively assess its suitability for energy application scenarios. Although the substrate was not completely deconstructed at the rather low temperature of 120 °C, the biomethane yield through whole slurry anaerobic digestion was 32% higher than that of unpretreated wheat straw. It was proposed that an increasing amount of soluble fractions was released at higher pretreatment temperatures, which consequently limited anaerobic digestion through the acidification or inhibition mechanism; therefore a lower biomethane yield was obtained. In contrast to the profile of anaerobic digestion, increasing the pretreatment temperature significantly facilitated bioethanol production through simultaneous saccharification and fermentation (SSF). When the hydrothermal pretreatment was performed at 210 °C, the ethanol yield was 229.5% higher than that of the untreated wheat straw. The possible reason was that at higher temperatures, the recalcitrant fraction of hemicellulose tended to solubilize through auto acid-catalyzed hydrolysis, which enhanced the accessibility of cellulose to cellulase enzymes. At very high hydrothermal temperatures (≥240 °C), the pretreated substrates were not suitable for biological conversion but were well suited for production of carbons with an ultra-high surface area. In conclusion, lower pretreatment temperatures are recommended for anaerobic digestion, moderate temperatures for SSF, and high temperatures for non-biological conversion to produce supercapacitor carbon electrodes.
Published Version
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