Hydrothermal Carbonization of Lignocellulosic Biomass
Hydrothermal carbonization (HTC) of lignocellulosic biomass is a pretreatment process to homogenize and densify diverse biomass feedstocks. The solid product is hydrophobic and friable with ultimate analysis similar to that of lignite, and is easily made
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Hydrothermal Carbonization of Lignocellulosic Biomass Charles J. Coronella, Joan G. Lynam, M. Toufiq Reza and M. Helal Uddin
Abstract Hydrothermal carbonization (HTC) of lignocellulosic biomass is a pretreatment process to homogenize and densify diverse biomass feedstocks. The solid product is hydrophobic and friable with ultimate analysis similar to that of lignite, and is easily made into durable, dense pellets. Byproducts include aqueous sugars, acids, carbon dioxide, and water. The process consists of treatment in hot (180–280 C) compressed water for short contact times, and has been demonstrated on woody biomass, agricultural residues, and grasses. HTC reactions include hydrolysis, dehydration, decarboxylation, condensation, polymerization, and aromatization. Nearly all hemicellulose is removed and converted to simple sugars and furfural. Cellulose begins to react at 200 C, and produces oligosaccharides, glucose, 5-HMF, and organic acids. Lignin is relatively inert. HTC reactions are relatively fast, with reaction times measured in minutes. Both hemicellulose and cellulose degrade by apparent first-order reaction kinetics, where hemicellulose exhibits an activation energy of 30 kJ mol-1, and that of cellulose is 73 kJ mol-1. There has been a flurry of research on HTC published recently, but little commercial activity. Innovative design is required for commercialization, and costs may be high, due to high pressure operation. However, as demand for biomass increases, HTC will surely play a role in enhancing supply chain logistics.
12.1 Introduction Progressing toward sustainable, renewable energy production is essential for our world in the next century. Fossil fuels, with their irreversible generation of greenhouse gases, cannot provide us with energy indefinitely. Biomass, which C. J. Coronella (&) J. G. Lynam M. T. Reza M. H. Uddin Chemical and Materials Engineering Department, University of Nevada, MS 170, Reno, NV 89557, USA e-mail: [email protected]
F. Jin (ed.), Application of Hydrothermal Reactions to Biomass Conversion, Green Chemistry and Sustainable Technology, DOI: 10.1007/978-3-642-54458-3_12, Springer-Verlag Berlin Heidelberg 2014
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takes in CO2 as it grows and uses sunlight as its power source, can play a pivotal role in weaning us from fossil fuels. Biomass encompasses many types of plant materials. To avoid the food-versusfuel conflict, only nonfood lignocellulosic biomass is considered appropriate for sustainable energy production. Such biomass includes woody biomass, grassy biomass, and agricultural residues from food production. Lignocellulosic biomass is a many-layered package including lignin, cellulose, hemicellulose, extractives, and inorganics (ash). Converting lignocellulosic biomass to useful forms of fuel presents challenges in handling, storage, and processing. As harvested (often on a seasonal basis), hydrophilic biomass has a high moisture content often rendering it perishable, as well as heavy and thus expensive to transport. Drying c
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