Briquetting of charcoal from sugar-cane bagasse fly ash (scbfa) as an alternative fuel

Brazil is the largest worldwide producer of alcohol and sugar from sugar-cane and has an extensive alternative program for car fuel which is unique. The objective of this work is to offer one management option of a solid residue produced by this industrial segment. The pressed sugar-cane bagasse is burned to produce steam and electricity by cogeneration. The combustion yields both bottom and fly ashes which contain high amounts of silicon oxide as a major component. Fly ash which contains a high volume (>30% by weight) of charcoal was used in this work. The ash was sieved to separate the thick charcoal from inorganic materials which are concentrated in the thinner fraction. The briquettes were hand pressed using charcoal mixed with a binder (starch) obtained from cassava flour (a tropical root). The results (density, mechanical resistance) obtained with 8% by weight of starch binder are presented here. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to characterize the ashes and the briquettes. The results show that sugar-cane bagasse fly ash (SCBFA) can be used to produce briquettes with an average density of 1.12 g cm^?3 and an average calorific value of 25,551 kJ/kg.     

A system dynamics approach for hospital waste management

Healthcare services provided by hospitals may generate some infectious wastes. Although a large percentage of hospital waste is classified as general waste, which has similar nature as that of municipal solid waste and, therefore, could be disposed in municipal landfills, a small portion of infectious waste has to be managed in the proper manner in order to minimize risk to public health. Many factors involved in the hospital waste management system often link to one another, which require a comprehensive analysis to determine the role of each factor in the system. In this paper, we present a hospital waste management model based on system dynamics to determine the interaction among factors in the system using a software package, Stella. A case study of the City of Jakarta, Indonesia is selected. The hospital waste generation is affected by various factors including the number of beds in the hospitals and the NIMBY (not in my back yard) syndrome. To minimize the risk to public health, we found that waste segregation, as well as infectious waste treatment prior to disposal, has to be conducted properly by the hospital management, especially when scavenging takes place in landfill sites in developing countries.     

Material Flows in Sweden 2004

This paper presents and discusses the method and results of account for material flows in Sweden for the year 2004. The results show that it is possible to compile material flow data from existing sources in the Swedish statistical system. By using the European classification system of goods, the Combined Nomenclature, as the basic unit of the data collection, both data collection and aggregation into material flow categories were made possible. Although these data exist in the statistical system, they are not easily available for the scientific community. This is due to several reasons, such as the aggregation of data in the system of statistics not corresponding to the material flow account structure and the fact that data on import and export of materials are organised differently than data for domestic extraction. Almost 50% of the material flows in Sweden are flows of minerals, mainly construction minerals followed by iron ores. Most of the extracted iron ores are exported. In comparison with other European countries this generates a unique situation with Sweden as the only net exporter of iron ores. The flow of biomass in terms of wood is also considerable (26% of the Swedish material flows in 2004). The domestic material consumption (inflow) per capita in 2004 was 8 tonnes minerals, 6 tonnes biomass and almost 3 tonnes of fossil fuels. Of the material flows of fossil fuels petroleum and natural gas dominates with 90%.     

Evaluation of Material Biodegradability in Real Conditions–Development of a Burial Test and an Analysis Methodology Based on Numerical Vision

This work validated a burial protocol for in situ testing and presents a robust, repeatable and time-saving technique to measure degraded areas in the sample, i.e. an image analysis method. 1440 specimens of degraded samples have been compiled in a data base. To this end, twenty samples presenting different levels of biodegradability (i.e. PHBV/HV, PLA, PCL, PCL-Starch, paper, PE, PE-Starch) were buried at 4 different locations and then disinterred at 4, 6, 9, 12, 18, and 24-month intervals. The biodegradation levels of these samples were determined by computing weight and area loss. Weight loss was measured after careful cleaning, whereas area loss was quantified using image analysis. Image analysis gives reliable information on visual pollution while only requiring a rudimentary and thus quicker cleaning of the samples.     

Wet oxidative regeneration of activated carbon loaded with reactive dye

Wet Oxidative Regeneration (WOR) of powdered activated carbon (PAC) and granular activated carbon (GAC) loaded with the reactive dyes, namely chemictive brilliant blue R and cibacron turquoise blue G, was studied. Attempts were made to regenerate the loaded carbons designated now as spent carbon. A slurry (10% w/v) of spent carbon in distilled water was oxidized by wet oxidation in the temperature range of 150-250 degrees C using oxygen partial pressures between 0.69-1.38 MPa in an 1 1 SS 316 autoclave. The percent regeneration was determined from a ratio, X(RC)/X(VC), corresponding to an equilibrium adsorption capacity of regenerated carbon/equilibrium adsorption capacity of virgin carbon from an initial adsorption period of 3 h. It was observed that the regeneration mainly occurred due to the oxidation of the adsorbates taking place on the surface of carbon. It was possible to regenerate the spent GAC and PAC to the extent of more than 98% (approximately X(RC)/X(VC) > 0.98) by wet oxidation. After four consecutive cycles of adsorption and regeneration using the same stocks of GAC, carbon weight loss observed at 200 degrees C was about 40%. SEM studies of the regenerated carbon showed widening of the pores and loss of structure between the adjacent pores as compared with the virgin carbon. PAC was found to be more suitable as compared with GAC for the adsorption and wet oxidative regeneration processes to treat the aqueous solution containing lower concentration of unhydrolyzed reactive dye. The suitability of wet oxidative regeneration is demonstrated at a bench scale to treat the synthetic reactive dye solution.     

Effect of microbial activity on the mobility of chromium in soils

The effect of microbial activity on the chemical state of chromium, in a contaminated soil located in the Rh?ne-Alpes region (France), has been investigated. This soil contained 4,700 mg kg(-1) Cr, with about 40% present in the soluble hexavalent form. Indigenous microbial activity was found to significantly reduce Cr(VI) to the less mobile form (III) when the soil was incubated at 30 degrees C in an aqueous medium containing glucose and nutrients. A Cr(VI)-reducing strain of Streptomyces thermocarboxydus was isolated from the contaminated soil. The strain was found to metabolize Cr(VI) in a similar manner as an exogenous inoculum of Pseudomonas fluorescens LB300, and to precipitate chromium as a Cr oxyhydroxide with a gammaCrOOH-like local structure. The Cr(VI)-reducing activity of S. thermocarboxydus was induced, or significantly accelerated, by the aggregation of bacterial cells or their adhesion to suspended solid particles, and was stimulated in pure culture by glycerol and chromate.     

Chemical Recycling of Polyamide Waste at Various Temperatures and Pressures Using High Pressure Autoclave Technique

Chemical recycling of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of 150, 200, 210, 220,230 and 240 °C and at various pressures of 100, 200, 300, 400, 500, 600 and 700 psi (pound per square inch). Viscosity average molecular weight of the polyamide waste sample was determined by Ostwald method and recorded as 1.928 × 10³. The reaction was found to be first order with velocity constant in order of 10⁻² min⁻¹. The velocity constant and percent conversion of depolymerization reaction at 240 °C and 700 psi pressure were recorded as 2.936 × 10⁻² min⁻¹ and 99.99% respectively. The velocity constant was obtained on the basis of measurement of amine value. Kinetic and thermodynamic parameters such as energy of activation, frequency factor, enthalpy of activation were found to be 10.6 kJ mole⁻¹, 0.3719 min⁻¹ and 6.3 kJ mole⁻¹ respectively, at the optimum conditions for maximum depolymerization of polyamide waste.     

Anaerobic biodegradation of cellulosic material: Batch experiments and modelling based on isotopic data and focusing on aceticlastic and non-aceticlastic methanogenesis

Utilizing stable carbon isotope data to account for aceticlastic and non-aceticlastic pathways of methane generation, a model was created to describe laboratory batch anaerobic decomposition of cellulosic materials (office paper and cardboard). The total organic and inorganic carbon concentrations, methane production volume, and methane and CO₂ partial pressure values were used for the model calibration and validation. According to the fluorescent in situ hybridization observations, three groups of methanogens including strictly hydrogenotrophic methanogens, strictly aceticlastic methanogens (Methanosaeta sp.) and Methanosarcina sp., consuming both acetate and H₂/H₂CO₃ as well as acetate-oxidizing syntrophs, were considered. It was shown that temporary inhibition of aceticlastic methanogens by non-ionized volatile fatty acids or acidic pH was responsible for two-step methane production from office paper at 35 °C where during the first and second steps methane was generated mostly from H₂/H₂CO₃ and acetate, respectively. Water saturated and unsaturated cases were tested. According to the model, at the intermediate moisture (150%), much lower methane production occurred because of full-time inhibition of aceticlastic methanogens. At the lowest moisture, methane production was very low because most likely hydrolysis was seriously inhibited. Simulations showed that during cardboard and office paper biodegradation at 55 °C, non-aceticlastic syntrophic oxidation by acetate-oxidizing syntrophs and hydrogenotrophic methanogens were the dominant methanogenic pathways.     

In situ remediation of arsenic in contaminated soils

In situ chemical fixation represents a promising and potentially cost‐effective treatment alternative for metal‐contaminated soils. This article presents the findings of the use of iron‐bearing soil amendments to reduce the leachability and bioaccessibility of arsenic in soils impacted by stack fallout from a zinc smelter. The focus of this investigation was to reduce the lead bioaccessibility of the soils through addition with phosphorus‐bearing amendments. However, as phosphorus addition was expected to increase arsenic mobility, the fixation strategy also incorporated use of iron‐bearing amendments to offset or reverse these effects. The findings of this investigation demonstrated that inclusion of iron‐bearing chemicals in the amendment formulation reduced arsenic leachability and bioaccessibility without compromising amendment effectiveness for reducing lead bioaccessibility. These results suggest that in situ chemical fixation has the potential to be an effective strategy for treatment of the impacted soils. © 2003 Wiley Periodicals, Inc.     

Graft Copolymerization of Methyl Acrylate onto Cellulosic Biofibers: Synthesis,Characterization and Applications

Graft copolymerization of cellulosic biopolymers with synthetic polymers is of enormous interest because of its application in biofiltration, biosorption, biomedical, biocomposites and various other eco-friendly materials. Synthesis of graft copolymers of methyl acrylate onto mercerized Grewia optiva biofibers using ferrous ammonium sulfate–potassium per sulfate as redox initiator in air was carried out. Different reaction parameters such as amount of solvent, monomer concentration, initiator molar ratio, reaction time and reaction temperature were optimized to get the maximum percentage of grafting. The graft copolymers thus formed were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis and differential thermogravimetric techniques. A plausible mechanism for explanation of the graft copolymerization reactions pattern shown is offered. The effect of grafting percentage on the physico–chemical properties of raw as well as grafted Grewia optiva biofibers has also been investigated. The graft copolymers have been found to be more moisture resistant and also showed better chemical and thermal resistance. Green polymer composites were also successfully prepared through compression molding technique by using grafted Grewia optiva biofibers as reinforcement.