Fluidized bed reactors in the waste-to-energy chain

by Piero Salatino - University of Naples "Federico II", Naples, Italy
Biomass- and waste-derived fuels provide an attractive and sustainable energy source. Fluidized bed combustion and gasification are among the most viable technologies for the exploitation of biogenic fuels, either alone or in combination with fossil fuels. However, the experience gained so far, from operation of lab- to full-scale FB combustors and gasifiers, has highlighted some critical issues associated with thermochemical conversion of biogenic fuels: solid fuel and volatile matter segregation along and across the reaction chamber; particle attrition/fragmentation and the associated loss of unburned carbon; diversity of combustion patterns and rates, as related to chemical composition and morphology of the parent biogenic fuels; ash behavior. There are measures to counteract these drawbacks, like the use of pelletized biomass- and waste-derived fuels and/or careful tuning of bed hydrodynamics. The aim of this lecture is to provide an overview of recent advances in the development of fluidized bed reactor technologies, and a systematic characterization of fuel properties relevant to the fluidized bed combustion and gasification of different types of biomass and nontoxic solid waste.




Manufacturing of Nanomaterials from Bio-wastes and Production of Eco-Friendly Bionanocomposites

by Sabu Thomas - Mahatma Gandhi University, Kottayam, India

Green chemistry started for the search of benign methods for the development of nanoparticles from nature and their use in the field of antibacterial, antioxidant, and antitumor applications. Bio wastes are eco-friendly starting materials to produce typical nanoparticles with well-defined chemical composition, size, and morphology. Cellulose, starch, chitin and chitosan are the most abundant biopolymers around the world.   All are under the polysaccharides family in which cellulose is one of the important structural components of the primary cell wall of green plants. Cellulose nanoparticles (fibers, crystals and whiskers) can be extracted from agrowaste resources such as jute, coir, bamboo, pineapple leafs, coir etc. Chitin is the second most abundant biopolymer after cellulose, it is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods and nanoparticles of chitin (fibers, whiskers) can be extracted from shrimp and crab shells. Chitosan is the derivative of chitin, prepared by the removal of acetyl group from chitin (Deacetylation). Starch nano particles can be extracted from tapioca and potato wastes. These nanoparticles can be converted into smart and functional biomaterials by functionalisation through chemical modifications (esterification, etherification, TEMPO oxidation, carboxylation and hydroxylation etc) due to presence of large amount of hydroxyl group on the surface. The preparation of these nanoparticles include both series of chemical as well as mechanical treatments; crushing, grinding, alkali, bleaching and acid treatments. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to investigate the morphology of nanoscale biopolymers. Fourier transform infra-red spectroscopy (FTIR) and x ray diffraction (XRD) are being used to study the functional group changes, crystallographic texture of nanoscale biopolymers respectively. Since large quantities of bio wastes are produced annually, further utilization of cellulose, starch and chitins as functionalized materials is very much desired. The cellulose, starch and chitin nano particles are currently obtained as aqueous suspensions which are used as reinforcing additives for high performance environment-friendly biodegradable polymer materials. These nanocomposites are being used as   biomedical composites for drug/gene delivery, nano scaffolds in tissue engineering and cosmetic orthodontics. The reinforcing effect of these nanoparticles results from the formation of a percolating network based on hydrogen bonding forces. The incorporation of these nano particles in several bio-based polymers have been discussed. The role of nano particle dispersion, distribution, interfacial adhesion and orientation on the properties of the eco friendly bio nanocomposites have been carefully evaluated.




Different pathways of resource recovery from anaerobic digestion of organic residues

by Hélène Carrere1, Florian Monlau2, Cecilia Sambusiti2, Abdellatif Barakat2, Elena Ficara3, Eric Trably1

1INRA, UR0050, Laboratoire de Biotechnologie de l’Environnement, 11100 Narbonne, France
2INRA, UMR 1208, Ingénierie des Agropolymères et Technologies Emergentes, 34060 Montpellier, France
3Politecnico di Milano, DICA, Environmental Section, 20133, Milano, Italy

Anaerobic digestion is a key process for urban solid waste management converting organic waste into biogas, mainly composed of methane and carbon dioxide, and a residue called digestate which is generally separated into solid and liquid fractions.
Based on an overview of the abundant literature published on municipal solid waste and lignocellulosic biomasses, the potentialities of anaerobic digestion processes will be presented. The first part of the lecture will discuss the interest of using pretreatment techniques to improve the conversion of wastes into biogas [1,2]. Some intermediary products of anaerobic digestion such as fatty acids, ethanol and hydrogen present a higher added value than methane. Different anaerobic process parameters and the selection of specific microbial consortia allow an optimal production of these products while preventing methane production in the so-called dark fermentation process [3]. The impact of waste pretreatment on the production of hydrogen and metabolites will also be discussed [1]. Dark fermentation effluents may be treated in anaerobic digestion to produce biohythane, consisting of a mixture of biohydrogen and methane, and leading a cleaner and more efficient combustion than that of methane alone.
In addition, digestates are rich in nitrogen, phosphorous and more or less stabilized carbon and can be used as fertilizers or soil improvers. More original uses of digestates have been proposed such as the conversion of the digestate solid fraction into activated biochar, bio-oil and syngas through thermal processes, or the use of nutrients present in the liquid fraction in biological processes such as algae growth or bioethanol production [4].

[1] F. Monlau, A. Barakat, E. Trably, C. Dumas, J.-P. Steyer and H. Carrère, Lignocellulosic Materials into BioHydrogen and BioMethane: Impact of structural features and pretreatment Critical Reviews in Environmental Science and Technology, 2013, 43, 260-322
[2] H. Carrere, G. Antonopoulou ,R. Affes, F. Passos, A. Battimelli, G. Lyberatos, I. Ferrer. Review of pretreatment strategies for improved feedstocks anaerobic biodegradability: from lab-scale research to full-scale application, Bioresource Technology, 199 (2016) 386-397
[3] X.M. Guo, E. Trably, E. Latrille, H. Carrère, J.P. Steyer, Predictive and explicative models of fermentative hydrogen production from solid organic waste: role of butyrate and lactate pathways. International Journal of Hydrogen Energy, 39 (2014) 7476-7485
[4] F. Monlau F.,C. Sambusiti, E. Ficara E., A. Aboulkas , A. Barakat , H. Carrere. New opportunities for agricultural digestate valorization : current situation and perspectives, Energy and Environmental Science,8 ( 2015) 2600-2621



Chemistry literacy as the key to promote general better waste management

by Liliana Mammino - University of Venda, South Africa

Solid wastes constitute a huge environmental and management problem because of their huge (and continuously increasing) amount and because of the variety of their nature. The first objective is that of reducing their amount, both at the origin (producing less waste) and through recycling. The presentation focuses on the types of solid waste for which the behaviour of individual citizens can bring significant impacts – which includes domestic wastes, but may also include wastes from microscale economy activities. The most important contribution from citizens is actively contributing to recycling, and also accepting the outcomes of reduction at the origin (e.g., in terms of simpler or no packaging of goods on sale). These contributions require conviction. People will take part in recycling options (e.g., by separating different types of domestic wastes according to their nature) if they are convinced of the importance of doing it. In turn, conviction can only be generated by information leading to the internalisation of relevant knowledge. The most important information about the impact of solid wastes on the environment and about the benefits of recycling is chemistry-based. Chemistry is the science of substances and, therefore, chemistry literacy is at the basis of understanding the appropriate ways of handling substances and materials both during their useful life and when they need to be disposed of.
After an overview of the main features of the solid waste issue, the presentation focuses on the importance of chemistry literacy for a positive response – by the public – to initiatives aimed at improving the management of solid wastes. Specific attention is also devoted to the African continent considering a variety of perspectives, including the potential economic benefits from micro- and small-scale initiatives for the implementation of recycling at local levels (community level and expansions from it). Concrete examples are included to illustrate and substantiate inferences and suggestions.