Benjamin Mauricio Martinez Castellanos, Omex Mohan, Vinoj Kurian
et al.
<p>In this study, a lab-scale flat plate die mill was used to evaluate the pelletization of three organic municipal solid waste (MSW) streams: digestate from anaerobic processes (DAP), source-separated organics (SSOs), and refuse-derived fuel (RDF). Different particle sizes (4, 8, 12 mm) with moisture contents (MCs) of 10 and 15% were processed through a 6 mm die. RDFs and SSOs demonstrated excellent durability, but DAPs did not. RDFs had a high heating value (HHV) of 21.49 MJ kg<sup>-1</sup>, twice that of DAPs (10.07 MJ kg<sup>-1</sup>). The SSOs’ HHV varied seasonally (13.88 MJ kg-1 in spring-summer, 19.47 MJ kg<sup>-1</sup> in winter). At a 12 mm particle size, 10 and 15% MC RDF pellets had the lowest throughput capacity (6.99 and 12.20 kg hr<sup>-1</sup>). Throughput capacity for 10 and 15% MC pelletized SSOs and RDFs decreased with larger particle sizes. The lowest specific energy consumption for 10 and 15% MC pelletized SSO and RDF was at 4 mm (256.99 kJ kg<sup>-1</sup>) and 8 mm (1432.69 kJ kg-1) particle sizes. Specific energy consumption increased with particle size for 10% MC pellets, except for RDFs. At a 10% MC, RDFs reached a maximum bulk density of 594 kg m<sup>-3</sup>, while SSO pellets achieved 730 kg m<sup>-3</sup>. These optimized pelletization parameters are suitable for potential scale-up and future thermochemical conversion research, promoting sustainable use of organic MSW and the circular economy.</p>
Benjamin Mauricio Martinez Castellanos, Omex Mohan, Vinoj Kurian
et al.
<p>In this study, a lab-scale flat plate die mill was used to evaluate the pelletization of three organic municipal solid waste (MSW) streams: digestate from anaerobic processes (DAP), source-separated organics (SSOs), and refuse-derived fuel (RDF). Different particle sizes (4, 8, 12 mm) with moisture contents (MCs) of 10 and 15% were processed through a 6 mm die. RDFs and SSOs demonstrated excellent durability, but DAPs did not. RDFs had a high heating value (HHV) of 21.49 MJ kg<sup>-1</sup>, twice that of DAPs (10.07 MJ kg<sup>-1</sup>). The SSOs’ HHV varied seasonally (13.88 MJ kg-1 in spring-summer, 19.47 MJ kg<sup>-1</sup> in winter). At a 12 mm particle size, 10 and 15% MC RDF pellets had the lowest throughput capacity (6.99 and 12.20 kg hr<sup>-1</sup>). Throughput capacity for 10 and 15% MC pelletized SSOs and RDFs decreased with larger particle sizes. The lowest specific energy consumption for 10 and 15% MC pelletized SSO and RDF was at 4 mm (256.99 kJ kg<sup>-1</sup>) and 8 mm (1432.69 kJ kg-1) particle sizes. Specific energy consumption increased with particle size for 10% MC pellets, except for RDFs. At a 10% MC, RDFs reached a maximum bulk density of 594 kg m<sup>-3</sup>, while SSO pellets achieved 730 kg m<sup>-3</sup>. These optimized pelletization parameters are suitable for potential scale-up and future thermochemical conversion research, promoting sustainable use of organic MSW and the circular economy.</p>
Pyrolysis is effective in reducing the volume of solid waste and sludge, and produces less pollutants than incineration and landfill, but the process still suffers from heavy metal pollution. Four types of intercalated-exfoliated modified vermiculite (UIV, DIV, TIV and 3IV) were prepared using urea, dimethylsulfoxide, tributyl phosphate and 3-aminopropyltriethoxysilane as intercalators for the control of Cd, Cr, Cu, Pb and Zn in municipal sewage sludge (MSL), paper mill sludge (PML), municipal domestic waste (MWA) and aged refuse (AFE). The larger the interlayer spacing of the vermiculite, the more favorable the retention of heavy metals. 3IV was the most effective additive, with an average retention of more than 75 % of all heavy metals at 450 ℃ for the four raw materials. Cr, Cu, Pb and Zn were all at low potential ecological risk (Pr), while Cd was moderate or considerable Pr, and the addition of 3IV reduced the Pr. Distribution of intercalators between vermiculite interlayers was haphazard, and interlayer spacing results were close to those of the experiment (except for tributyl phosphate). The reactive electrons mainly flowed from the Highest Occupied Molecular Orbital (HOMO) of vermiculite flakes to the Lower Unoccupied Molecular Orbital (LUMO) of heavy metal chlorides. In contrast, the reactive electrons mostly flowed from the HOMO of heavy metal oxides to the LUMO of vermiculite flakes. Heavy metal oxides were more readily adsorbed on vermiculite flakes than heavy metal chlorides, and the adsorption capacity of Cr and Zn was stronger than that of Cd, Pb and Cu.
A large part of municipal solid waste (MSW) still goes to landfills, representing an environmental concern. A circular economy approach can enable safe management of MSW while mitigating the increasing energy needs when waste is used as a feedstock in energy production processes (waste to energy). Currently, MSW can be converted into refuse-derived fuel (RDF) through mechanical and biological treatment processes. This study analyzes the status of MSW and RDF production, as well as its main destinations in Portugal and Europe. The legislation applied, possible energy-recovery routes, and challenges associated with energy recovery are discussed throughout this paper. This research finds that the production of RDF in Portugal has been neglected, mostly because of RDF composition being quite heterogeneous and its poor fuel properties. Therefore, the need to improve and upgrade the characteristics and properties of RDF for waste-to-energy processes was detected. RDF can be pretreated to be further applied to waste-to-energy and waste-to-gas processes, such as incineration and gasification. The technology readiness level data, costs, and SWOT analysis allowedto assess that although incineration is the most mature and widely used technology, gasification becomes more attractive, having lower costs and gaseous emissions, proving to be more efficient and sustainable for MSW and RDF conversion.
A small amount of leachate with complex composition will be produced during the compressing of municipal solid waste in refuse transfer stations. In this study, the freeze-melt method, a green and efficient wastewater treatment technology, was used to treat the compressed leachate. The effects of freezing temperature, freezing duration, and ice melting method on the removal rates of contaminants were investigated. The results showed that the freeze-melt method was not selective for the removal of chemical oxygen demand (COD), total organic carbon (TOC), ammonia-nitrogen (NH3-N) and total phosphorus (TP). The removal rate of contaminants was positively correlated with freezing temperature and negatively correlated with freezing duration, and the slower the growth rate of ice, the higher the purity of ice. When the compressed leachate was frozen at -15 °C for 42 h, the removal rates of COD, TOC, NH3-N and TP were 60.00%, 58.40%, 56.89% and 55.34%, respectively. Contaminants trapped in ice were removed during the melting process, especially in the early stages of melting. The divided melting method was more beneficial than the natural melting method in removing contaminants during the initial stage of melting, which contributes to the reduction of produced water losses. This study provides a new idea for the treatment of small amounts of highly concentrated leachate generated by compression facilities distributed in various corners of the city.
A long-term feasibility analysis of a 100 ton per day mechanical biological treatment (MBT) plant for municipal solid waste (MSW) valorization and material and energy recovery was carried out. It involves the material recovery and segregation stage (MRSS), organic extraction (pulping), thermophilic anaerobic digestion (AD), composting, effluent treatment plant (ETP), and biogas genset stages producing: 11.90% recyclables, 33% refused derived fuel (RDF), 5% compost of total waste received, 70 m3/day recyclable water and 0.435 MWh/day electricity. The biogas and methane yield were 0.535 and 0.350 m3/kg VSadded (avg.), respectively, with 40% VS removal (avg total solids (TS) 10%). Less than 3% (inert) of total waste received was subjected to landfill disposal. The MBT plant's revenue generation is 995 US$ per day/148 tons ($ 6.72/ton) waste processed. The gross OPEX is 24 US$/ton making the net OPEX of 17 US$/ton (minus revenue), which could be considered as the excellent OPEX for MSW based MBT plants as per global benchmarks. Further, local usage of RDF can significantly reduce the OPEX to 14 US$/ton, as almost 16% of the OPEX goes towards RDF disposal to cement companies located at a distance of 200-500 km from the MBT plant site. As per LCA study, the total GHG emissions have been calculated to be -25.68 tons CO2 eq./100 tons MSW. The negative emissions result from the export of electricity, compost, and RDF as well as recycling of paper and plastic products. Our study presents a cutting-edge scenario of all-inclusive recycling, recovery, and reuse loop of MSW direly required for accomplishing a circular economy.
Angelika Sita Ouedraogo, Robert Scott Frazier, Ajay Kumar
Disposal of municipal solid wastes (MSW) remains a challenge to minimize its impacts on the environment and human health. Landfilling, currently the most common method used for MSW disposal, occupies land space and leads to soil and air emissions. Gasification, an alternative MSW disposal method, can convert waste to energy, but can also lead to soil and air emissions and is a more extensive operation. In this study, life cycle assessments (LCA) of the two disposal methods (landfilling without energy recovery and gasification) were compared to understand impacts on environment and health. The LCA was conducted following the ISO 14040 standards with one ton of MSW as the functional unit. The life cycle inventory was obtained from published journals, technical reports, LandGEM, HELP and GREET database. The impact assessment was done using TRACI 2.1 and categorized into eight groups. The LCA revealed that landfilling is a higher contributor in global warming, acidification, smog formation, eutrophication, ecotoxicity and human health cancer and non-cancer categories. The negative environmental impacts of MSW landfilling can be primarily attributed to the fate of leachate loss and landfill gas, while those of the MSW gasification can be attributed to the disposal of its solid residues.
Botagoz Kuspangaliyeva, Botakoz Suleimenova, Dhawal Shah
et al.
Efficient waste management, including proper utilization of municipal solid waste (MSW), is imperative for a sustainable future. Among several management options, pyrolysis and combustion of MSW has regained interest because of improved combustion techniques. This work aims to investigate the thermal conversion and combustion characteristics of refuse derived solid fuel (RDF) samples and its individual compounds collected from Nur-Sultan’s MSW landfills. The waste-derived solid RDF samples originally consist of textile, mixed paper, and mixed plastic. In particular, the samples, including RDF and its three constituent components, were analyzed in the temperature range of 25 to 900 °C, at three different heating rates, by thermogravimetric method. The gross calorific value for RDF derived from Nur-Sultan’s MSW was determined to be 23.4 MJ/kg. The weight loss rates of the samples, differential thermogravimetry (DTG), and kinetic analysis were compared between individual RDF components and for the mixed RDF. Combustion kinetics models were calculated using Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman methods. The results revealed that first decomposition of RDF samples was observed at the range of 180–370 °C. Moreover, the activation energy for conversion of RDF was observed to be the highest among the constituent components and gradually decreased from 370 to 140 kJ/kmol.
Growing municipal solid waste (MSW) generation is a source of environmental, economic, and social concerns, especially in developing world megacities where poor MSW practices prevail. Mexico City (CDMX), one of the world's largest megacities, daily produces ∼ 13,073 Mg of MSW whose management poses a tremendous challenge to local authorities and calls for additional research to conceive sound MSW strategies. This study evaluates the fossil energy use, GHG emissions, resource recovery, and economic cost dimensions of current and five alternative MSW paths in CDMX to compare their performance and identify more sustainable MSW practices for the megacity. Impacts and benefits from the MSW paths were modeled using 2018 MSW generation data, information supplied by local authorities, and literature values. Current MSW path consumes ∼ 387 MJfossil, generates ∼ 501 kg-CO2e, and costs ∼ 57 USD2018 per Mg of MSW managed while it only valorizes < 33% of total MSW mostly via informal truck-picking. The alternative MSW paths considerably reduce GHG emissions (∼129-360 kg-CO2e/Mg) and enhance MSW valorization (∼47-88%) though, they entail higher fossil energy consumption (447-582 MJfossil/Mg) and, in general, higher cost expenditures (43-208 USD2018/Mg). Heavy reliance on landfilling, large GHG emissions, and low MSW valorization make current MSW path in CDMX unsustainable. Incineration-based MSW paths perform better in most aspects evaluated but their high costs seem prohibitive. Results suggest MSW paths featuring open windrow composting, mechanical-biological pre-treatment, material recovery facilities, and refuse-derived fuel production may be more appropriate to improve the sustainability of CDMX MSW management.
The study examined municipal solid wastes characteristics of Gosa dumpsite at Abuja, Nigeria. Waste characterization has not yet been given adequate attention in management of waste in Nigeria and it is a major problem that affects waste materials handling and recovery processes. Wastes samples from Gosa waste dump site, Abuja, were randomly collected and subjected to moisture content, composition, density and size distribution determinations according to prescribed standards in literature. The moisture content of the Gosa waste solid was 19.3%. The results of the characterization of the Gosa municipal solid wastes show 34% organic, 10% paper, 28% plastic, 2% glass, 6% metal, 4% fabric, 2% rubber and 14% dust. The average density of glass, metal, plastic, fabric, rubber, paper, organic and dust materials were 0.044 kg/m3, 0.045 kg/m3, 0.176 kg/m3, 0.043 kg/m3, 0.042 kg/m3, 0.074 kg/m3, 0.143 kg/m3 and 0.098 kg/m3, respectively. The size distribution of the Gosa solid waste ranges from 10-28 cm for metals and plastics and 3-13 cm for paper and glass. The rubber had size ranges from 8-23 cm while size ranges of organic was from 3-6 cm. The large presence of organic, plastic, paper and metal wastes at Gosa waste dump site, is an indication that the municipal solid wastes can be sorted, recycled and processed to other useful products, using the characteristics as a guide.Keyword: Characterization, Density, Municipal Solid Waste, Size Distribution, Waste Management
Background. The generation and management of solid waste pose potential adverse impacts on human health and the environment. Objective. The present study examines the operational performance of municipal solid waste (MSW) disposal in the Wa Municipality, Ghana. Methods. The study applied both qualitative and quantitative research methods and modelled the Wa Municipality's MSW disposal system using the municipal solid waste decision support tool (MSW DST). Acid gases (sulphur oxides and nitrogen oxides) and total particulate matter that have a direct impact on human health were set as the objective functions for modelling five MSW disposal scenarios. The modelled scenarios were: 1) landfill disposal only; 2) composting and landfill disposal; 3) composting, incineration, refuse derived fuels (RDF) and landfill disposal; 4) separation, composting, incineration, RDF and landfill disposal; and 5) separation, transfer, material recovery, composting, incineration, RDF and landfill disposal. The pollutants chosen as indicators for substance flow analysis included lead, cadmium, arsenic, mercury, copper, chromium, and zinc. Results. Scenarios 4 and 5 produced the least engineering cost of 1 150 000 US $/year for the entire MSW disposal system, whereas scenario 2 produced the highest cost of 1 340 000 US $/year. Scenario 5 produced the least average health impacts of −5.812E-04 lbs/year, while scenario 2 generated the highest engineering cost and produced the highest average health impact of 9.358E-05 lbs/year. Scenarios 5 and 4, which included waste-to-energy conversion in the systems, produced the lowest average health impacts (−5.812E-04 lbs/year and −5.611E-04 lbs/year, respectively). Conclusions. The adoption of an integrated solid waste management concept, including waste-to-energy technologies, will not only help to lessen MSW disposal hazards, but also to produce alternative sources of energy for Ghana and other developing countries. Competing Interests. The authors declare no competing financial interests
The data collected from the Environmental Protection Agency (EPA) of Pakistan indicate that collection and disposal of municipal solid waste in the city of Karachi is underdeveloped. The studies conducted in 2012 showed the composition of solid waste is organics 47.2%, paper 15.9%, plastic 11.3%, bread 4.2%, bones 3.8%, metal 2.7%, glass 2.5%, textile 1.9%, wood 0.7%, and miscellaneous 9.8%. The city government collects only 48% of the total waste generated, of which 88% is disposed in dumping sites. This study aimed to assess the current practices of solid waste management in Karachi and suggests a quantitative approach to decision making obtained from decision support software (DSS) . The application of the DSS tool demonstrated that the landfilling of refuse-derived fuel/solid recovered fuel can be replaced by waste-to-energy options. The DSS tool can offer support for decision makers not only for planning process, but also for the assessment of adopted solutions.
Gas migration rule is of great significance to the safe disposal of landfill. In this article, a gas–solid coupling model was developed and used to simulate the effects of various factors on gas migration. The simulation results showed that gas pressure in landfill decreased with the increase of extraction pressure, anisotropy ratio, coverage gas permeability, extraction well depth, and coverage thickness. The maximum value of gas pressure could reach 683 Pa. Among these factors, extraction pressure played the largest role in the gas pressure, while coverage thickness played the smallest role in it. The radius of influence (RoI) and gas flow rate increased with the increase of extraction pressure, refuse gas permeability, coverage thickness, and the extraction well depth, but with the decrease of coverage gas permeability. The effect of extraction well depth on RoI and gas flow rate was the most significant. When extraction well depth increased from 0.5 landfill height to 0.9 landfill height, the maximum values of RoI and extraction volume increased by 20 m and 20 m3/hr, respectively. It was suggested that the design of landfill gas (LFG) collection system should consider the influence of various factors in practical engineering.
There are excellent opportunities for Juba city (South Sudan) to provide a wide range of urban services including waste management in the informal settlement, which have a direct positive impact on resident’s health, creation of employment, and poverty reduction. This study shows how government involves the community in the solid waste management in order to solve the problem of uncollected waste after the failure of the municipal council to do so. The study examines the performance of the existing solid waste collection and disposal practices, resident’s willingness to participate, and identifies problems relating to the solid waste management system of Juba. Methods used in the study are, questionnaires, interviews and observations. It has been found that there is illegal dumping of waste and over 90% of the people participates the questionnaire refuse paying collection fees. The success of peoplebased solid waste management depends on the participation of the residents and has a great relation with its local economy. The findings from this study could be used in preparing an improved solid waste collection process.
The purpose of this study is nutrient resources recovery by achieving the optimal chemical oxygen demand (COD) and carbon to nitrogen ratio (C/N) in co-composting wastewater treatment plant sludge with Municipal Solid Wastes (MSW). In this effort, the co-composting has been conducted in form of a case study in the southern region of Caspian Sea. In this research, 192 tests were carried out on four series of samples examined in terms of waste to sludge ratio, different aeration period, the percent of porous materials and the moisture content. This study was carried out at a temperature of 65 °C for a 15 day period by application of the in-vessel system and shows that the best ratio for waste to sludge is 2:1, while the 8 hour period is the best aeration period. The porous material which can be added to the composting process is limited to 15% in weight. In other words, any more or less amount of this material will adversely impact the process. Moreover, this research suggests that the sludge dewatering is not required in such processes. In Addition, the efficiency of both COD and C/N reductions equals to about 40%.