Energy yield potentials from the anaerobic digestion of common animal manure in Bangladesh

This study provides previously unavailable field data relating to the biogas and methane yields from supervised authentic anaerobic digesters using the most common animal manure in Bangladesh: cow dung, poultry litter and town cattle market straw which are found to produce biogas yields of 0.034, 0.030 and 0.142 m3/kg respectively, with methane concentrations of 60% and 62% and 74% respectively and total solids of 19, 23 and 45 respectively. It also reports indications that in unsupervised plant issues with underfeeding, improper water mixing and irregular feeding are very common – all of which can significantly reduce yields. The figures above should thus be treated as maximum, optimum field values. These results provide reliable data for use in scaling up for national energy and investment planning, as they related directly to common scenarios of family smallholdings, common sized poultry farms and town cattle markets in Bangladesh where there is a reliance on combustion of local wood and dung biomass for cooking, creating air pollution, health and environmental degradation issues

Partitioning of heavy metals in sewage sludge incineration

The behaviour of seven metals (Cd, Cr, Cu, Mn, Ni, Ph, Zn) during sewage sludge incineration was studied in two pilot plant tests performed with a rotary drum furnace at 900 degrees C. A first group of metals (Cr, Cu, Mn, Ni) show similar concentrations in bottom and fly ashes. In contrast, lead, cadmium and zinc concentrations in fly ashes are one or two order of magnitude higher than those in bottom ash. A thermodynamic model was used to predict metal behaviour assuming perfect mixing and equilibrium conditions in the combustion chamber. The model may predict in a satisfactory way the behaviour of Cr, Cu, Mn, Ni (" non volatile" metals) and of Cd and Pb ("volatile" metals), with the exception of Zn, that is not predicted to volatilize in the combustion chamber, in contrast with the clear zinc enrichment in fly ash. The use of the thermodynamic model was proved to be very useful in understanding and predicting metal behaviour during sludge incineration

High-frequency ultrasounds for the decontamination and intensive stabilization of sewage sludge.

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Dioxins, furans and polycyclic aromatic hydrocarbons emissions from a hospital and cemetery waste incinerator

An experimental campaign was carried out on a hospital and cemetery waste incineration plant in order to assess the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polycyclic aromatic hydrocarbons (PAHs). Raw gases were sampled in the afterburning chamber, using a specifically designed device, after the heat recovery section and at the stack. Samples of slags from the combustion chamber and fly ashes from the bag filter were also collected and analyzed. PCDD/Fs and PAHs concentrations in exhaust gas after the heat exchanger (200-350 degrees C decreased in comparison with the values detected in the afterburning chamber. Pollutant mass balance regarding the heat exchanger did not confirm literature findings about the de novo synthesis of PCDD/Fs in the heat exchange process. In spite of a consistent reduction of PCDD/Fs in the flue gas treatment system (from 77% up to 98%), the limit of 0.1 ng ITEQ Nm(-3) at the stack was not accomplished. PCDD/Fs emission factors for air spanned from 2.3 up to 44 mu g ITEQ t(-1) of burned waste, whereas those through solid residues (mainly fly ashes) were in the range 41-3700 mu g ITEQ t(-1). Tests run with cemetery wastes generally showed lower PCDD/F emission factors than those with hospital wastes. PAH total emission factors (91-414 mu g kg(-1) of burned waste) were in the range of values reported for incineration of municipal and industrial wastes. In spite of the observed release from the scrubber, carcinogenic PAHs concentrations at the stack (0.018-0.5 mu g Nm(-3)) were below the Italian limit of 10 mu g Nm(-3). (c) 2007 Elsevier Ltd. All rights reserved.An experimental campaign was carried out on a hospital and cemetery waste incineration plant in order to assess the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polycyclic aromatic hydrocarbons (PAHs). Raw gases were sampled in the afterburning chamber, using a specifically designed device, after the heat recovery section and at the stack. Samples of slags from the combustion chamber and fly ashes from the bag filter were also collected and analyzed. PCDD/Fs and PAHs concentrations in exhaust gas after the heat exchanger (200-350 degrees C decreased in comparison with the values detected in the afterburning chamber. Pollutant mass balance regarding the heat exchanger did not confirm literature findings about the de novo synthesis of PCDD/Fs in the heat exchange process. In spite of a consistent reduction of PCDD/Fs in the flue gas treatment system (from 77% up to 98%), the limit of 0.1 ng ITEQ Nm(-3) at the stack was not accomplished. PCDD/Fs emission factors for air spanned from 2.3 up to 44 mu g ITEQ t(-1) of burned waste, whereas those through solid residues (mainly fly ashes) were in the range 41-3700 mu g ITEQ t(-1). Tests run with cemetery wastes generally showed lower PCDD/F emission factors than those with hospital wastes. PAH total emission factors (91-414 mu g kg(-1) of burned waste) were in the range of values reported for incineration of municipal and industrial wastes. In spite of the observed release from the scrubber, carcinogenic PAHs concentrations at the stack (0.018-0.5 mu g Nm(-3)) were below the Italian limit of 10 mu g Nm(-3). (c) 2007 Elsevier Ltd. All rights reserved

Multifaceted approach for characterization of solid residues from sludge incineration

The Italian Water Research Institute (IRSA) carried out sludge incineration tests on a demonstrative plant equipped with a circulating fluidized bed furnace. Aim of this paper is to present the potential applicability of non-conventional techniques for solid residues characterization. Results of five tests performed under different operating conditions are discussed. Incineration solid residues were sampled from the cyclone, downstream the furnace ( cyclone ash, CA), and from the bag filter ( filter ash, FA). Different techniques were used by the Mechanical and Industrial Engineering Department of the "Roma TRE" University, which cooperated with IRSA in the research project, to characterize incineration products and to correlate with process parameters. The X-ray Diffraction (XRD) technique was used to estimate the amount of sand, lost from the furnace, in CA and FA samples. Particle size distribution was measured using Low Angle Laser Light Scattering (LALLS). Scanning Electron Microscopy associated with Energy Dispersive Spectroscopy (SEM/EDS) was used to correlate size and shape of individual particles with chemical composition. This multifaceted approach to characterize incineration residues appears promising, providing additional and complementary information to the traditional chemical characterization

Microbial diversity in innovative mesophilic/thermophilic temperature-phased anaerobic digestion of sludge

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