Impact of different particle size distributions on anaerobic digestion of the organic fraction of municipal solid waste

Particle size may significantly affect the speed and stability of anaerobic digestion, and matching the choice of particle size reduction equipment to digester type can thus determine the success or failure of the process. In the current research the organic fraction of municipal solid waste was processed using a combination of a shear shredder, rotary cutter and wet macerator to produce streams with different particle size distributions. The pre-processed waste was used in trials in semi-continuous ‘wet’ and ‘dry’ digesters at organic loading rate (OLR) up to 6 kg volatile solids (VS) m?3 day?1. The results indicated that while difference in the particle size distribution did not change the specific biogas yield, the digester performance was affected. In the ‘dry’ digesters the finer particle size led to acidification and ultimately to process failure at the highest OLR. In ‘wet’ digestion a fine particle size led to severe foaming and the process could not be operated above 5 kg VS m?3 day?1. Although the trial was not designed as a direct comparison between ‘wet’ and ‘dry’ digestion, the specific biogas yield of the ‘dry’ digesters was 90% of that produced by ‘wet’ digesters fed on the same waste at the same OLR.<br/

Polyethylene and Polypropylene Nanocomposites Based on Polymerically - Modified Clay Containing Alkylstyrene Units

Sodium montmorillonite was modified with a new polymeric surfactant. The high molecular weight of the surfactant appears to have led to incomplete cation exchange of the clays, but did promote nanocomposite formation with polyethylene and polypropylene. X-ray diffraction combined with transmission electron microscopy revealed a mixed nanocomposite morphology. The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis, while flammability of the nanocomposites was evaluated by cone calorimetry. A significant 40% reduction in peak heat release rate was observed at 10% organo-clay (3% inorganic clay) loading with an even higher 50% reduction at a loading level of 16% modified clay (5% inorganic clay). Despite possible plasticization effects by the polymers used as an organic modification for the clays, the mechanical properties such as Young\u27s modulus and elongation were not severely impacted by the nanocomposite formation

A Carbocation Substituted Clay and its Styrene nanocomposite

A substituted tropylium ion can be ion-exchanged onto montmorillonite to give a novel organically-modified clay. One can prepare a polystyrene nanocomposite of this clay by emulsion, but not bulk, polymerization. This is the first example of a clay that contains a carbocation and its use to prepare a polymer-clay nanocomposite. Both the clay and its nanocomposites exhibit outstanding thermal stability. Characterization by X-ray diffraction, transmission electron microscopy, cone calorimetry, thermogravimetric analysis and the evaluation of mechanical properties shows that a mixed intercalated-exfoliated nanocomposite is obtained

Preparation and flammability properties of polyethylene-clay nanocomposites

Polyethylene (PE)–clay nanocomposites have been prepared using melt blending in a Brabrender mixer. X-ray diffraction and transmission electron microscopy were used to characterize the nano-structure of these composites while the thermal stability was evaluated from thermogravimetric analysis and the flammability parameters using cone calorimetry. It is found that the PE–clay nanocomposites have a mixed immiscible-intercalated structure and there is better intercalation when maleic anhydride is combined with the polymer and clay to be melt blended. The reduction in peak heat release rate is 30–40%

Polymerically Modified Layered Silicates: An Effective Route to Nanocomposites

Polymer/clay nanocomposites have been under an extensive investigation for about 15 years. Traditional methods to modify the clay are usually limited to small organic cations, preferably containing long alkyl chain(s), which are exchanged with the inorganic cations in the clay gallery. This article provides a comprehensive review on the strategies for clay modification using polymeric surfactants or polycations: from the synthesis of such surfactants, through the preparation of the polymerically modified clays, and to the fabrication of the respective polymer nanocomposites and their properties

Co-digestion of source segregated domestic food waste to improve process stability

Cattle slurry and card packaging were used to improve the operational stability of food waste digestion, with the aim of reducing digestate total ammoniacal nitrogen concentrations compared to food waste only. Use of cattle slurry could have major environmental benefits through reducing greenhouse gas emissions associated with current management practices; whilst card packaging is closely linked to food waste and could be co-collected as a source segregated material. Both options increase the renewable energy potential whilst retaining organic matter and nutrients for soil replenishment. Co-digestion allowed higher organic loadings and gave a more stable process. A high ammonia inoculum acclimated more readily to cattle slurry than card packaging, probably through supplementation by trace elements and micro-organisms. Long-term operation at a 75-litre scale showed a characteristic pattern of volatile fatty acid accumulation in mono-digestion of food waste, and allowed performance parameters to be determined for the co-digestion substrates.<br/