Technoeconomic aspects of alternative municipal solid wastes treatment methods

This paper considers selected treatment technologies for comingled domestic and similar wastes and provides technoeconomic data and information, useful for the development of strategic management plans. For this purpose, treatment technologies of interest are reviewed and representative flow diagrams, along with material and energy balances, are presented for the typical composition of wastes in Greece; possible difficulties in the use of treatment products, along with their management implications, are discussed, and; cost functions are developed, allowing assessment of the initial capital investment and annual operating costs. Based on the latter, cost functions are developed for predicting the normalized treatment costs of alternative methods (in €/t of MSW treated), as function of the quantity of MSW processed by plants built and operated (a) by municipality associations, and (b) by private enterprises. Finally, the alternative technologies considered are evaluated on the basis of their cost aspects, product utilization and compatibility with the EU waste framework Directive 2008/98.     

Aging and compressibility of municipal solid wastes

The expansion of a municipal solid waste (MSW) landfill requires the ability to predict settlement behavior of the existing landfill. The practice of using a single compressibility value when performing a settlement analysis may lead to inaccurate predictions. This paper gives consideration to changes in the mechanical compressibility of MSW as a function of the fill age of MSW as well as the embedding depth of MSW. Borehole samples representative of various fill ages were obtained from five boreholes drilled to the bottom of the Qizhishan landfill in Suzhou, China. Thirty-one borehole samples were used to perform confined compression tests. Waste composition and volume-mass properties (i.e., unit weight, void ratio, and water content) were measured on all the samples. The test results showed that the compressible components of the MSW (i.e., organics, plastics, paper, wood and textiles) decreased with an increase in the fill age. The in situ void ratio of the MSW was shown to decrease with depth into the landfill. The compression index, Cc, was observed to decrease from 1.0 to 0.3 with depth into the landfill. Settlement analyses were performed on the existing landfill, demonstrating that the variation of MSW compressibility with fill age or depth should be taken into account in the settlement prediction.     

Energy from gasification of solid wastes

Gasification technology is by no means new: in the 1850s, most of the city of London was illuminated by "town gas" produced from the gasification of coal. Nowadays, gasification is the main technology for biomass conversion to energy and an attractive alternative for the thermal treatment of solid waste. The number of different uses of gas shows the flexibility of gasification and therefore allows it to be integrated with several industrial processes, as well as power generation systems. The use of a waste-biomass energy production system in a rural community is very interesting too. This paper describes the current state of gasification technology, energy recovery systems, pre-treatments and prospective in syngas use with particular attention to the different process cycles and environmental impacts of solid wastes gasification.     

Feasibility study for thermal treatment of solid tire wastes in Bangladesh by using pyrolysis technology

In this study on the basis of lab data and available resources in Bangladesh, feasibility study has been carried out for pyrolysis process converting solid tire wastes into pyrolysis oils, solid char and gases. The process considered for detailed analysis was fixed-bed fire-tube heating pyrolysis reactor system. The comparative techno-economic assessment was carried out in US$ for three different sizes plants: medium commercial scale (144 tons/day), small commercial scale (36 tons/day), pilot scale (3.6 tons/day). The assessment showed that medium commercial scale plant was economically feasible, with the lowest unit production cost than small commercial and pilot scale plants for the production of crude pyrolysis oil that could be used as boiler fuel oil and for the production of upgraded liquid-products.     

Effects of plastics in anaerobic digestion of urban solid wastes

Anaerobic digestion is a possible method for treating urban solid wastes. This pilot plant study was undertaken to ascertain the effect of plastic refuse on the anaerobic digestion process of municipal solid wastes. The air-blown polyethylene film present in the air classified light fraction of solid waste from Pompono Beach, Florida, U.S.A. was removed by visual separation. Control digesters operating on this substrate, produced more gas than test digesters to which the plastic scraps had been returned.     

Pyrolysis kinetics behavior of solid tire wastes available in Bangladesh

Pyrolysis kinetics of available bicycle/rickshaw, motorcycle and truck tire wastes in Bangladesh have been investigated thermogravimetrically in a nitrogen atmosphere at heating rates of 10 and 60 degrees C/min over a temperature range of 30-800 degrees C. The three tire wastes exhibited similar behaviors in that, when heating rate was increased, the initial reaction temperature decreased but the reaction range and reaction rate increased. The percentage of total weight loss was higher for truck tire waste and lower for bicycle/rickshaw tire waste. The pyrolysis of truck tire waste was found to be easier than that of bicycle/rickshaw and motorcycle tire wastes while it was comparatively more difficult for motorcycle tire waste. The overall rate equation for the three tire wastes has been modeled satisfactorily by one simplified equation from which the kinetic parameters of unreacted materials based on the Arrhenius form can be determined. The predicted rate equation compares fairly well with the measured TG and DTG data. DTA curves for all of the samples show that the degradation reactions are three main exotherms and one endotherm.     

Pilot installation for the thermo-chemical characterisation of solid wastes

The increasing production and the large variety of wastes require operators of thermal treatment units to continuously adapt the installations or the functioning parameters to the different physical and chemical properties of the wastes. Usually, the treated waste is encountered in the form of heterogeneous mixtures. The classical tests such as thermogravimetry and calorimetric bomb operate component by component, separately. In addition to this, they can analyse only small quantities of waste at a time (a few grams). These common tests are necessary but insufficient in the global waste analysis in the view further thermal treatment. This paper presents an experimental installation, which was designed and built at the CNRS Science Division, Department of Industrial Methods, Compiègne University of Technology, France. It allows the determination of waste thermal and chemical properties by means of thermal treatment. Also, it is capable of continuously analysing significant quantities of waste (up to 50kg/h) as compared to the classical tests and it can work under various conditions: The installation reproduces the process conditions from incinerators or pyrolysis reactors. It also provides complete information on the kinetics of the waste thermal degradation and on the pollutant emissions. Using different mixtures of components present in the municipal solid waste and also in the reconstituted MSW samples, we defined a series of criteria for characterising waste behaviour during the stages of the main treatment process such as: feeding, devolatilisation/oxidation, advancement, solid residue evacuation, and pollutants emission.     

Reuse of municipal solid wastes incineration fly ashes in concrete mixtures

This study is aimed at assessing the feasibility of concrete production using stabilized m.s.w. (municipal solid waste) incineration fly ashes in addition to natural aggregates. The tested fly ashes were washed and milled, then stabilized by a cement-lime process and finally were reused as a "recycled aggregate" for cement mixture production, in substitution of a natural aggregate (with dosage of 200-400 kg m(-3)). These mixtures, after curing, were characterized with conventional physical-mechanical tests (compression, traction, flexure, modulus of elasticity, shrinkage). In samples containing 200 kg(waste) m(-3)(concrete), a good compressive strength was achieved after 28 days of curing. Furthermore, concrete leaching behavior was evaluated by means of different leaching tests, both on milled and on monolithic samples. Experimental results showed a remarkable reduction of metal leaching in comparison with raw waste. In some cases, similar behavior was observed in "natural" concrete (produced with natural aggregates) and in "waste containing" concrete.     

Abundance of 14C in biomass fractions of wastes and solid recovered fuels

In recent years thermal utilization of mixed wastes and solid recovered fuels has become of increasing importance in European waste management. Since wastes or solid recovered fuels are generally composed of fossil and biogenic materials, only part of the CO₂ emissions is accounted for in greenhouse gas inventories or emission trading schemes. A promising approach for determining this fraction is the so-called radiocarbon method. It is based on different ratios of the carbon isotopes ¹⁴C and ¹²C in fossil and biogenic fuels. Fossil fuels have zero radiocarbon, whereas biogenic materials are enriched in ¹⁴C and reflect the ¹⁴CO₂ abundance of the ambient atmosphere. Due to nuclear weapons tests in the past century, the radiocarbon content in the atmosphere has not been constant, which has resulted in a varying ¹⁴C content of biogenic matter, depending on the period of growth. In the present paper ¹⁴C contents of different biogenic waste fractions (e.g., kitchen waste, paper, wood), as well as mixtures of different wastes (household, bulky waste, and commercial waste), and solid recovered fuels are determined. The calculated ¹⁴C content of the materials investigated ranges between 98 and 135 pMC.     

进口初级产物类物品的固体废物属性鉴别研究

利用红外光谱、气相色谱/质谱联用、液相色谱/质谱联用、核磁共振波谱、原子发射光谱、凝胶渗透色谱、X-射线荧光光谱等多种分析方法,剖析了申报进口的一个未知有机物品的组分、含量和理化指标;阐述了进口物品的产生来源,探讨了其固体废物属性。结果表明,样品不属于固体废物。呈现了一个以回收物料为原料加工的未知有机初级产物固体废物属性鉴别的全过程,为从事进口固体废物相关的人员提供参考,另外,初级产物固体废物属性鉴别非常复杂,建议制定详细的鉴别标准。     

Accelerated carbonation treatment of industrial wastes

The disposal of industrial waste presents major logistical, financial and environmental issues. Technologies that can reduce the hazardous properties of wastes are urgently required. In the present work, a number of industrial wastes arising from the cement, metallurgical, paper, waste disposal and energy industries were treated with accelerated carbonation. In this process carbonation was effected by exposing the waste to pure carbon dioxide gas. The paper and cement wastes chemically combined with up to 25% by weight of gas. The reactivity of the wastes to carbon dioxide was controlled by their constituent minerals, and not by their elemental composition, as previously postulated. Similarly, microstructural alteration upon carbonation was primarily influenced by mineralogy. Many of the thermal wastes tested were classified as hazardous, based upon regulated metal content and pH. Treatment by accelerated carbonation reduced the leaching of certain metals, aiding the disposal of many as stable non-reactive wastes. Significant volumes of carbon dioxide were sequestrated into the accelerated carbonated treated wastes.     

上海市生活垃圾全程分类模式的研究和实践

提出了生活垃圾全程分类模式。通过试点,着重论述与该模式相对应的工作内容和方法,对城市生活垃圾的减量化、资源化、无害化推进具有指导意义。     

Thermodynamic estimation of minor element distribution between immiscible liquids in Fe-Cu-based metal phase generated in melting treatment of municipal solid wastes

Waste electrical and electronic equipment (WEEE) has become an important target in managing material cycles from the viewpoint of not only waste management and control of environmental pollution but also resource conservation. This study investigated the distribution tendency of trace elements in municipal solid waste (MSW) or incinerator ash, including valuable non-ferrous metals (Ni, Co, Cr, Mn, Mo, Ti, V, W, Zr), precious group metals (PGMs) originated from WEEE (Ag, Au, Pd, Pt), and others (Al, B, Pb, Si), between Fe-rich and Cu-rich metal phases by means of simple thermodynamic calculations. Most of the typical alloying elements for steel (Co, Cr, Mo, Nb, Ni, Si, Ti, V, and W) and Rh were preferentially distributed into the Fe-rich phase. PGMs, such as Au, Ag, and Pd, were enriched in the Cu-rich phase, whereas Pt was almost equally distributed into both phases. Since the primary metallurgical processing of Cu is followed by an electrolysis for refining, and since PGMs in crude copper have been industrially recovered from the resulting anode slime, our results indicated that Ag, Au, and Pd could be effectively recovered from MSW if the Cu-rich phase could be selectively collected.     

The effect of lignin and sugars to the aerobic decomposition of solid wastes

A series of experimental runs were conducted from 1995 to 1999 in Madison (WI, USA) with the goal to investigate the biodegradation process of seven (7) solid waste components and mixtures of them under near optimal aerobic conditions. It was shown that substrates with high initial lignin contents or high initial HWSM contents were observed to have relatively low and high degradation extents, respectively. Two linear equations were derived that correlate degradation extent (as indicated by the volatile solids reduction) to initial lignin and initial HWSM contents separately. The lignin equation was compared to a similar equation previously developed for anaerobic environments by Chandler et al. (Predicting methane fermentation biodegradability. In: Biotechnology and Bioengineering Symposium No. 10 (1980) New York: John Wiley & Sons). With comparison to the Chandler formula, lignin was found to be less inhibitory to the overall substrate decomposition in aerobic environments compared to anaerobic ones. Cellulose loss contributed to a higher than 50% to the overall dry mass loss for all substrates studied. In addition, the cellulose to lignin (C/L) ratio appeared to be a relatively accurate compost maturity indicator, since it reduced to a value less than 0.5 for most substrates that had reached their degradation extent.     

Reutilization of thermostable polyester wastes by means of agglomeration with phenolic resins

We report on the possibility of obtaining organic polymeric matrixes allowing the development of new high performance fire-resistant products by recycling downsized thermostable waste materials. Phenolic resins have been used as binders for recycled waste. Furthermore, considering that reinforced plastic triturations have superior properties (chemical, mechanical, water resistance, etc.) to wood agglomerates, significant advantages over conventional materials are anticipated. In summary, we propose a viable solution to some of the known problems caused by the consumption of wood and to the needs of strengthened plastic processing engineering. Using resins as a binder, several fire-resistant prototypes were prepared from polyester waste, and their mechanical properties, thermal stability, and fire-resistant properties were analyzed.     

Continuous high-solids anaerobic co-digestion of organic solid wastes under mesophilic conditions

With increasing concerns over the limited capacity of landfills, conservation of resources, and reduction of CO(2) emissions, high-solids (dry) anaerobic digestion of organic solid waste (OSW) is attracting a great deal of attention these days. In the present work, two dry anaerobic co-digestion systems fed with different mixtures of OSW were continuously operated under mesophilic conditions. Dewatered sludge cake was used as a main seeding source. In reactor (I), which was fed with food waste (FW) and paper waste (PW), hydraulic retention time (HRT) and solid content were controlled to find the maximum treatability. At a fixed solid content of 30% total solids (TS), stable performance was maintained up to an HRT decrease to 40 d. However, the stable performance was not sustained at 30 d HRT, and hence, HRT was increased to 40 d again. In further operation, instead of decreasing HRT, solid content was increased to 40% TS, which was found to be a better option to increase the treatability. The biogas production rate (BPR), CH(4) production yield (MPY) and VS reduction achieved in this condition were 5.0m(3)/m(3)/d, 0.25 m(3) CH(4)/g COD(added), and 80%, respectively. Reactor (II) was fed with FW and livestock waste (LW), and LW content was increased during the operation. Until a 40% LW content increase, reactor (II) exhibited a stable performance. A BPR of 1.7 m(3)/m(3)/d, MPY of 0.26 m(3) CH(4)/g COD(added), and VS reduction of 72% was achieved at 40% LW content. However, when the LW content was increased to 60%, there was a significant performance drop, which was attributed to free ammonia inhibition. The performances in these two reactors were comparable to the ones achieved in the conventional wet digestion and thermophilic dry digestion processes.     

Bio-processing of solid wastes and secondary resources for metal extraction - A review

Metal containing wastes/byproducts of various industries, used consumer goods, and municipal waste are potential pollutants, if not treated properly. They may also be important secondary resources if processed in eco-friendly manner for secured supply of contained metals/materials. Bio-extraction of metals from such resources with microbes such as bacteria, fungi and archaea is being increasingly explored to meet the twin objectives of resource recycling and pollution mitigation. This review focuses on the bio-processing of solid wastes/byproducts of metallurgical and manufacturing industries, chemical/petrochemical plants, electroplating and tanning units, besides sewage sludge and fly ash of municipal incinerators, electronic wastes (e-wastes/PCBs), used batteries, etc. An assessment has been made to quantify the wastes generated and its compositions, microbes used, metal leaching efficiency etc. Processing of certain effluents and wastewaters comprising of metals is also included in brief. Future directions of research are highlighted.