Potential applications of nanotechnology in thermochemical conversion of microalgal biomass

The rapid decrease in fossil reserves has significantly increased the demand of renewable and sustainable energy fuel resources. Fluctuating fuel prices and significant greenhouse gas (GHG) emission levels have been key impediments associated with the production and utilization of nonrenewable fossil fuels. This has resulted in escalating interests to develop new and improve inexpensive carbon neutral energy technologies to meet future demands. Various process options to produce a variety of biofuels including biodiesel, bioethanol, biohydrogen, bio-oil, and biogas have been explored as an alternative to fossil fuels. The renewable, biodegradable, and nontoxic nature of biofuels make them appealing as alternative fuels. Biofuels can be produced from various renewable resources. Among these renewable resources, algae appear to be promising in delivering sustainable energy options. Algae have a high carbon dioxide (CO2) capturing efficiency, rapid growth rate, high biomass productivity, and the ability to grow in non-potable water. For algal biomass, the two main conversion pathways used to produce biofuel include biochemical and thermochemical conversions. Algal biofuel production is, however, challenged with process scalability for high conversion rates and high energy demands for biomass harvesting. This affects the viable achievement of industrial-scale bioprocess conversion under optimum economy. Although algal biofuels have the potential to provide a sustainable fuel for future, active research aimed at improving upstream and downstream technologies is critical. New technologies and improved systems focused on photobioreactor design, cultivation optimization, culture dewatering, and biofuel production are required to minimize the drawbacks associated with existing methods. Nanotechnology has the potential to address some of the upstream and downstream challenges associated with the development of algal biofuels. It can be applied to improve system design, cultivation, dewatering, biomass characterization, and biofuel conversion. This chapter discusses thermochemical conversion of microalgal biomass with recent advances in the application of nanotechnology to enhance the development of biofuels from algae. Nanotechnology has proven to improve the performance of existing technologies used in thermochemical treatment and conversion of biomass. The different bioprocess aspects, such as reactor design and operation, analytical techniques, and experimental validation of kinetic studies, to provide insights into the application of nanotechnology for enhanced algal biofuel production are addressed

Modelling of the pyrolysis of biomass particles. Studies on kinetics, thermal and heat transfer effects

The present work provides a rationally-based model to describe the pyrolysis of a single solid particle of biomass. As the phenomena governing the pyrolysis of a biomass particle are both chemical (primary and secondary reactions) and physical (mainly heat transfer phenomena), the presented model couples heat transport with chemical kinetics. The thermal properties included in the model are considered to be linear functions of temperature and conversion, and have been estimated from literature data or by fitting the model with experimental data. The heat of reaction has been found to be represented by two values: one endothermic, which prevails at low conversions and the other exothermic, which prevails at high conversions. Pyrolysis phenomena have been simulated by a scheme consisting of two parallel reactions and a third reaction for the secondary interactions between charcoal and volatiles. The model predictions are in agreement with experimental data regarding temperature and mass-loss histories of biomass particles over a wide range of pyrolysis conditions. On pr\ue9sente dans cet article un mod\ue8le s'appuyant sur des bases rationnelles pour d\ue9crire la pyrolyse d'une particule solide simple de biomasse. Consid\ue9rant que les ph\ue9nom\ue8nes gouvernant la pyrolyse de la particule de biomasse sont \ue0 la fois chimiques (r\ue9actions primaires et secondaires) et physiques (principalement des ph\ue9nom\ue8nes de transfert de mati\ue8re), le mod\ue8le pr\ue9sent\ue9 couple le transport de chaleur avec la cin\ue9tique chimique. Les propri\ue9t\ue9s thermiques incluses dans le mod\ue8le sont consid\ue9r\ue9es comme \ue9tant des fonctions lin\ue9aires de la temp\ue9rature et de la conversion et ont \ue9t\ue9 estim\ue9es \ue0 partir de donn\ue9es pubi\ue9es dans la litt\ue9rature ou en adaptant le mod\ue8le aux donn\ue9es exp\ue9rimentales. On a trouv\ue9 que la chaleur de la r\ue9action \ue9tait repr\ue9sent\ue9e par deux valeurs: une valeur endothermique qui pr\ue9domine \ue0 de faibles conversions et une valeur exothermique qui pr\ue9domine \ue0 des conversions \ue9lev\ue9es. Les ph\ue9nom\ue8nes de pyrolyse ont \ue9t\ue9 simul\ue9s par un sch\ue9ma comportant deux r\ue9actions parall\ue8les et une troisi\ue8me r\ue9action pour les interactions secondaires charbon-volatils. Les pr\ue9dictions du mod\ue8le montrent un bon accord avec les donn\ue9es exp\ue9rimentales sur la temperature et l'histoire de la perte massique des particules de biomasse pour une vaste gamme de conditions de pyrolys

Energetic potential and kinetic behavior of peats

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