Na+/K+/Mg2+/Ca2+ expansion-modified vermiculite and calcination expansion (700 °C, 800 °C and 900 °C)-modified vermiculite (700-Mg-V, 800-Mg-V and 900-Mg-V) were prepared as additives to control the emission of five heavy metals (Zn, Cr, Cu, Pb, and Cd) during the pyrolysis of municipal sewage sludge, paper mill sludge, municipal domestic waste, and aged refuse. Mg2+-Modified vermiculite obtained via thermally activated calcination at 800 °C retained 65% of heavy metals from all raw materials at 450 °C. Zn, Cr, and Cu retained nearly 90%. Although modified vermiculite could reduce the ecological risk, Cd had an ecological risk level higher than Zn, Cr, Cu, and Pb. The fine textural properties, laminated morphology, and expansion capacity of modified vermiculite were positively correlated with its retention of heavy metals. Heavy metals interacted with the (002) surface of vermiculite, and the reactions were mainly concentrated near the 17-O and surrounding atoms. The heavy-metal monomers were less capable of binding to the (002) surface of vermiculite than the oxides and chlorides of heavy metals. The effect of heavy-metal oxides and chlorides binding to the (002) surface of vermiculite was related to heavy metals.
Estefani Rondón Toro, Ana López Martínez, Amaya Lobo García de Cortázar
Most municipalities in developing countries lack technical and economic resources to improve their municipal solid waste management (MSWM) system. Therefore, tools are needed that enable the most appropriate solutions to be identified to put waste to better use. This study presents an easy-to-apply sequential methodology for the analysis of MSWM alternatives. The method consists of two stages: (1) screening available technologies based on a small set of key variables; (2) ordering the selected alternatives by a combination of multicriteria methods that integrate local priorities. For this second stage, a basic series of technical, environmental, economic and social indicators is proposed. The methodology is applied to a case study where current management is limited to mixed municipal solid waste (MSW) disposal in a landfill without gas recovery. Seven options for implementing energy recovery in landfill, using mechanical plants to recover part of recyclable material, treating the organic fraction, and employing refuse-derived fuel and/or waste to energy incineration, were evaluated together with the current situation and considering four scenarios. The results identify various alternatives that allow the sustainability of MSWM in the case study to improve. Notwithstanding, today, it is necessary to introduce economic instruments that discourage final disposal to make municipal waste recovery viable.
The failure of Zimbabwean local authorities to implement contemporary waste management technology, combined with refuse management incapacity exposes handlers of solid waste to work-related diseases and accidents. The study sought to use Murewa Rural District Council (RDC) as a case study and a mixed-method that triangulated qualitative and quantitative research methodologies was employed as a method of inquiry. The study established that, in Murewa, there is an irregular garbage collection schedule which results in piles of uncollected refuse on roadsides, street corners and other undesignated areas. The illegal dumping of refuse and overflowing of garbage bins have become an eyesore in Murewa Township Centre. The people employed to clean this mess are often ill equipped to clean the garbage in hygienic ways as they often use their bare hands to shovel the garbage from dumpsites and overloaded bins into the refuse collection trucks. In doing this, these workers are exposed to biological hazards such as bacteria, fungi, viruses, parasites and cysts. To minimise the associated hazards, the study suggests, among other things, that the Murewa Rural District Council should improve workplace safety and health for employees by modifying workplace and process design and by adhering to the hazard identification and risk assessment methodology.
Miia Liikanen, J. Havukainen, Ednilson Viana
et al.
Abstract Landfill disposal has thus far been the predominant treatment method for municipal solid waste (MSW) throughout Brazil, including Sao Paulo city. Environmentally sustainable development of MSW management in Sao Paulo necessitates a stepwise reduction of landfilling. However, ever increasing MSW generation poses the challenge of managing increasing MSW volumes while simultaneously modernizing the MSW management system. In this study, the environmental impacts of the current MSW management system and future alternatives in the city were assessed by means of life cycle assessment (LCA) to determine a pathway towards more environmentally sustainable MSW management. The assessed impact categories were global warming, acidification and eutrophication potentials. Potential future alternatives included the stepwise reduction of landfilling by the introduction of composting, anaerobic digestion and mechanical-biological treatment (MBT). The results of the study indicated that the environmental impacts of MSW management in Sao Paulo can be most effectively diminished by anaerobic digestion of source separated organic waste and MBT of MSW, on condition that the produced refuse-derived fuel (RDF) is utilized in cement production as a substitute for coal. The other utilization option for RDF, incineration, would increase the environmental impacts of MSW management due to the low amount of avoided emissions resulting from electricity substitution since average electricity production in Brazil is dominated by hydropower. Sensitivity analyses indicated, however, that the environmental impacts of incineration might decrease with different modeling assumptions, e.g. the modeling assumption regarding the kind of electricity production substituted by electricity production from MSW. Nevertheless, the main findings of the study remained the same and they are in line with the previous literature.
Life cycle assessment (LCA) was used to evaluate and compare three different categories of management systems for municipal solid waste (MSW) in Brazil: (1) mixed waste direct disposal systems, (2) separate collection systems, based on wet-dry streams, and (3) mixed waste mechanical-biological systems, including materials recovery. System scenarios were built around main treatment techniques available and applicable in developing countries, and considered barriers as well as potential synergies between waste management and other industrial production. In the first category systems, we measured the impact magnitude of improper disposal sites (semi-controlled and controlled dumps) still used for approximately 40% of collected MSW, and found that sanitary landfills could decrease it 3-5 fold (e.g. GWP, from 1100-1200 to 250-450 kg CO2 eq. t-1 waste). As an alternative, waste incineration did not show significant benefits over sanitary landfilling, due to limitations in energy utilization and the low-carbon background electricity system. Category two of systems, revealed recycling benefits and the necessity as well as potential risks of biological treatment for wet streams. Simple wet-dry collection could result in relatively high levels of contamination in compost outputs, which should be mitigated by intensive pre- and post-treatment. Potential impact of air emissions from biological degradation processes was important even after anaerobic digestion processes. Biogas upgrading and use as vehicle fuel resulted in bigger savings compared to direct electricity production. Lastly, category three, mechanical-biological systems, displayed savings in most environmental impact categories, associated with materials recovery for recycling and refuse-derived fuel (RDF) production and utilization in cement manufacturing.
The plastics from municipal solid waste (MSW) were modified to improve cleanness for adding value. The stir and sonication were performed as cleaning processes. Xylene, tetrachloroethylene, chloroform, acetone and toluene were used as solvent cleaning. The most suitable cleaning process was sonication method with cleaning time of 5 min and the appropriate solvent was xylene for washing the plastic wastes for further study in terms of thermo-mechanical and rheological properties. The cleaning process was successful as evidence in thermogravimetric analysis (TGA) results. The properties of new plastics, cleaned plastic wastes and plastic wastes were compared and analyzed. Tensile strength of the specimens from plastic wastes was slightly decreased; however, elongation and impact strength of cleaned plastic wastes and plastic wastes sharply dropped as compared to new plastics. Tensile modulus of cleaned plastic wastes was slightly better than that of new plastics. Thermal stability of plastic waste was slightly lower than that of new plastic. Shear storage modulus (Gʹ), shear loss modulus (Gʺ) and shear viscosity (η) of new plastics showed the maximum value; on the other hand, those properties of cleaned plastic wastes and plastic wastes were similar. The cleaning method with solvent did not destroy thermo-mechanical and rheological properties of the cleaned plastic wastes.
Abstract Industrial ecology based symbiotic system approach is applied to Indian municipal solid waste (MSW) for population size of one million, taking various alternative techniques: anaerobic digestion (AD), compost, refuses derived fuel (RDF), incineration and gasification. Considering the virtual operation of the existing plants for production of electricity and products, the economic and environmental evaluation of each technique is presented. For environmental impact assessment global warming, acidification, photochemical oxidation and eutrophication categories are considered. The conceptual analysis depicts that AD has maximum tendency to reduce global warming (123 tonne CO2 eq./day) along with the economic benefits of 19099 INR/day (293 $/day). Gasification shows maximum reduction in acidification, photochemical oxidation and eutrophication by 189 kg SO2 eq./day, 33 kg C2H4 eq./day and 12 kg PO4 eq./day with economic benefits of 46956 INR/day (722 $/day). Integrated operation of AD and gasification gives maximum economic benefits (INR 66056/day or 1016 $/day) with highest reduction in environmental impact (for all categories) as compared to a single technology and any other combination of technologies. Industrial ecology approach for MSW management system affects the economic and environmental results to significant level that can influence the policy and decision making.