Rapid urbanization in developing countries leads to a dramatic increase in solid waste production, with serious socio-economic and ecological impacts. In order to avoid the associated hazards, particularly those related to human health and the environment, solid waste management is indispensable. Disposal of municipal waste that predominantly comprises household and commercial refuse has become a daunting task for local governments and municipalities of Pakistan. Issues related to both inadequacy of service delivery and inappropriate disposal signify that waste management should be high on the local environment policy agenda. In particular, the external cost of waste management is high, and cost recovery of refuse collection may cause the exclusion of many households and additional costs on the households that avail themselves of the service. In this study, we carried out an evaluation of the health damage caused by improper waste disposal in a sample of heterogeneous households. The study shows a framework for evaluating the damages caused by inadequate waste management practices. The results indicate that irregular disposal in the vicinity of residents causes illness: respondents living within 100 m are more vulnerable to malaria, dengue, and asthma than those living more than 500 m away. Moreover, the findings highlight that households lack knowledge of waste hazards and 75.9% of waste is not segregated. We suggest a subsidized waste collection and disposal service provided either by the local government or by outsourcing.
Aged refuse with a landfill age of 1.5 years was collected from a municipal solid waste landfill with high kitchen waste content and mixed with soil as biocover material for landfill. A series of laboratory batch tests was performed to determine the methane oxidation potential and optimal mixing ratio of landfill cover soil modified with aged refuse, and the effects of water content, temperature, CO2/CH4, and O2/CH4 ratios on its methane oxidation capacity were analyzed. The microbial community analysis of aged refuse showed that the proportions of type I and type II methane-oxidizing bacteria were 56.27% and 43.73%, respectively. Aged refuse could significantly enhance the methane oxidation potential of cover soil, and the optimal mixing ratio was approximately 1:1. The optimal temperature and water content were about 25 °C and 30%, respectively. Under the conditions of an initial methane concentration of 15% and an O2/CH4 ratio of 0.8–1.2, the measured methane oxidation rate was negatively correlated with the O2/CH4 ratio. The maximum methane oxidation capacity measured in the test reached 308.5 (μg CH4/g)/h, indicating that the low-age refuse in the landfill with high kitchen waste content is a biocover material with great application potential.
The existence of acid gas and tar in syngas of municipal solid waste gasification limits its downstream utilization as a clean energy source. Here, we investigated the catalytic removal of HCl and tar. The key parameters affecting the catalytic reaction, including space velocity, temperature, the amounts of active metals in the catalyst and the carrier material, were studied, targeting optimized operating conditions for enhanced syngas purification. The morphology, mineral phases, surface area and pore size before and after the reaction were investigated to understand the mechanism to dominate the reaction. The results showed that the removal rate of CaO adsorbent and HCl reached 96% at 400 °C. When the space velocity ratio was 1.0 and the temperature was 400 °C, HCl removal (97%) by NaAlO2 was even better. Nevertheless, clogging was observed for NaAlO2 via the BET test after reaction to jeopardize its durability. A level of 25% Ni doping on Zr1-x(Cex)O2 support provides high stability for tar removal. This is because the Zr1-x(Cex)O2 carrier has higher carbon deposition resistivity than the Al2O3 carrier. The EDX results confirmed that a large amount of C (79.3%) was accumulated on the commercial catalyst surface supported by Al2O3 (25% Ni-based). As for the temperature, a temperature higher than 800 °C could not enhance the efficiency of tar removal, likely due to catalyst deactivation. Carbon deposition and agglomeration are the two main causes of catalyst deactivation. At 800 °C, 25% Ni-based synthetic catalyst can convert 48.5 ± 19.4% tar to low molecular weight organic compounds. By contrast, such a conversion rate under the same temperature only accounted for 5.0 ± 6.8% based on a commercial catalyst. These insights point to the important role of catalyst support materials.
Abstract Municipal solid waste classification is a major livelihood project, while the classified materials are deficiently utilized, especially the inert waste. In this study, a composite biological trickle reactor, packed with foam concrete, waste textile, animal bone and aged refuse, was developed for the treatment of mature landfill leachate, and the function of reaction factors were investigated systematically. Results indicated that under the optimum conditions with mixed filler, temperature of 30 °C, hydraulic loading of 40 L/(m3·d), and aeration rate of 1.8 L/(h·L), the average removal rates of chemical oxygen demand, total nitrogen, ammonia nitrogen and total phosphorus were 85.02 %, 76.00 %, 99.90 % and 96.83 %. The reactor presented well buffering performance after 100 days operation, with a slightly accumulation of organic and nitrogen substances. Biological analysis showed that the main phyla in all fillers were Actinobacteria and Proteobacteria. The microbial diversity and richness of waste textile were inferior to those of animal bone, aged refuse and foam concrete. In the operation system, the alternate aerobic–anoxic–anaerobic environment was structured, and the contaminants removal was due to the comprehensive function of adsorption, promotional biotreatment and chemical precipitation. All the results demonstrated that this novel trickle reactor was an excellent choice for leachate treatment because of the low cost and superior efficiency.
As in many developing countries, municipal solid waste (MSW) management is one of the most significant challenges facing urban communities in Algeria. The effective management of solid waste involves the application of various treatment methods, and technologies to ensure the protection of public health and the environment. This research work aimed to examine potential production and utilization of refuse-derived fuel (RDF) from MSW to be used as a substitute fuel in cement kilns in Algeria. After receiving the input waste, sieves were used to categorize MSW according to size. The waste fractions >80 mm were subjected to a drying process in an open-air area and had been turned periodically in order to increase the dry matter (DM). A cost study was performed to evaluate the environmental and economic savings of RDF utilization in the cement industry. At the end of the drying process, as a consequence of the waste moisture reduction, the low heating value was found to be 16 MJ kg−1, and the DM 87%. Concerning heavy metal content, their concentrations were within the limits set by the European Committee for Standardization (CEN)/TC 343 standardization. The chlorine content was around 0.37% to 0.80%. The feasibility study of adding RDF as a substitute fuel in the cement industry showed that when 15% of RDF is used, the RDF consumption will be 4.7 metric tonnes (Mt) h−1, which will save 4347.2 Nm3 h−1 of natural gas and 0.3 Mt h−1 in carbon dioxide emissions, with a net gas cost saving of 65 USD h−1.
Abstract As municipal landfills are still the prevailing option for solid waste management in Brazil, there is a high possibility to recover combustible materials from both municipal and industrial waste streams with high calorific value through Refuse Derived Fuel (RDF). RDF can be utilized as substitute fuels in cement and other industries that could, in turn, reduce energy consumption and the landfill space for waste disposal. However, relevant policies for use of RDF in Brazil are unclear due to the lack of systematic socioeconomic assessment concerning cost, benefit, and risk aspects. This paper is aimed to present a system dynamics modeling analysis to estimate the availability of potential recyclable waste streams from municipal and industrial sectors for RDF production in Brazil and discuss possible policy interventions. The model was simulated based on a 20-year timeframe in accordance with possible waste management policies in Espirito Santo (a Brazilian state). The results provide the annual waste availability from four different routes with respect to the pessimistic, intermediate, and optimistic scenarios considered. With the partial implementation of the actions indicated in the proposed solid waste management policy, it is envisioned that there will be sufficient waste streams for RDF production under dynamic uncertainties, given the limited cost-benefit-risk trade-off assessment. In addition to the direct benefits of sustainable RDF production as a substitute for fossil fuels in the cement industry, the indirect environmental benefits are salient as the regulations for circular economy can be functional in the future.
Abstract The energy-contained fraction of the municipal solid waste (MSW) is called refuse-derived fuel (RDF). RDF has a diverse blend of various materials and thus its physical properties and chemical composition are not predictable. Pelletization is one way to reduce the variability of RDF for applications like combustion. In this research, a typical RDF sample was constructed by blending four components of paper, plastic, wood and household organics. The entire blend was subjected to size reduction, drying and wetting. The influence of particles passed through 2, 4 and 6-mm grinder screen size and moisture contents 15, 20, 25 and 30% w.b. on the durability and density of pellets was investigated. The 4-mm RDF sample consumed higher energy and produced pellets with a lower durability than pellets from larger particles. The 6-mm grinder screen produced large pieces of paper and plastics that reduced the free flow of the blend into the pellet die. The RDF sample with an initial moisture content of 20% consumed the lowest pelletization energy. The force vs. deformation curve for compaction of the material to form pellets exhibited rigid material characteristics.
T. Marques, York Castillo Santiago, M. Renó
et al.
In this work, an energetic and environmental evaluation of the electricity generation process through refuse-derived fuel (RDF) gasification coupled to a gas microturbine (GM) was performed. Two scenarios are considered with different gasification agents in RDF gasification modeling: air and air enriched with oxygen. A thermodynamic chemical equilibrium approach was used to analyze the gasification parameters. The results of RDF gasification indicate a maximum value of syngas low heating value (LHV) equal to 8.0 MJ/Nm3, obtained for an equivalence ratio of 0.3. The use of these syngas in the gas microturbine produces 79.6 kW of electrical power. For the environmental evaluation of gasification and electricity generation systems, the Life Cycle Assessment methodology was employed. The calculated environmental impacts indicate that the emission of contaminants from fossil fuel combustion (in the stage of transport by heavy load vehicles) and that the electricity consumption for equipment operation (in the stage of municipal solid waste pretreatment) contributes to environmental pollution. On the other hand, electricity generation through GM presented lower environmental impact for all analyzed categories, suggesting that the electricity generation from gas obtained from gasification could be a viable option for thermochemical conversion of RDF and its subsequent energetic use.
The combustible fraction of municipal solid waste (MSW) is called refuse-derived fuel (RDF). RDF is a blend of heterogeneous materials and thus its handling is challenging. Pelletization is an efficient treatment to minimize the heterogeneity. In this research, typical RDF compositions were prepared by mixing several mass fractions of paper, plastic, household organic and wood. The collected compositions were ground, wetted to 20% moisture content (wet basis) and pelletized. Increasing the plastic content from 20% to 40% reduced the pelletization energy but increased the pellet’s calorific value. Pellets with higher plastic content generated more dust when exposed to shaking. Making durable pellets with 40% plastic content needed an increase in die temperature from 80 °C to 100 °C. Increasing the paper content from 30% to 50% increased the durability but consumed higher energy to form pellets. Paper particles increased the friction between pellet’s surface and die wall as was evident from expulsion energy. Force versus displacement curve for material compression revealed that the RDF compositions have rigid material characteristics.
A field excavation of refusewitha short-termlandfillage from the Qingdao Xiaojianxi municipal solid waste (MSW) landfill was conducted. The physical composition and chemical properties of refuse with landfill ages of 1-4 years were studied, and the emission characteristics of odorous pollutants during the excavation period were monitored. The refuse aged 1-2 years has a higher proportion of combustible material than that the refuse aged 3-4 years, and the volatile content and calorific value in refuse aged 1-2 years were also higher than those in refuse aged 3-4 years, indicating that the refuse with a short-term landfill age was more suitable for incineration than refuse with a long-term landfill age. The pH and availablephosphorus (AP) gradually increased with increasing landfill age, while the total Kjeldahlnitrogen (TKN) and organic matter (OM) decreased. The contents of the heavy metals Cu, Zn, Ni, Pb and As generally decreased with landfill age, especially in refuse aged 2-4 years, whereas the Cr content showed no significant differences in refuse aged 1-4 years. The main odorous pollutants emitted during the excavation and screening periods were ammonia (NH3) and carbon disulfide (CS2), and the odor intensity of excavated refuse aged 1-3 years was higher than that of refuse aged 4 years. Under the condition of a small excavation area and continuous deodorization, the pollution intensity can meet the discharge standards of the factory boundary.
Abstract The authors determined the morphological composition of refuse derived fuel (RDF) produced in Latvia and Lithuania by manually sorting. The parameters of RDF (moisture, net calorific value, ash content, carbon, nitrogen, hydrogen, sulphur, chlorine, metals) was determined using the EN standards. Comparing obtained results with data from literature, authors have found that the content of plastic is higher but paper and cardboard is lower than typical values. Results also show that the mean parameters for RDF can be classified with the class codes: Net heating value (3); chlorine (3); mercury (1), and responds to limits stated for 3rd class of solid recovered fuel. It is recommended to separate biological waste at source to lower moisture and ash content and increase heating value for potential fuel production from waste.