Municipal Solid Waste Components Research Articles

Thermal decomposition of expanded polystyrene in a pebble bed reactor to get higher liquid fraction yield at low temperatures

Expanded polystyrene is one of the polymers produced in large quantities due to its versatile application in different fields. This polymer is one of the most intractable components in municipal solid waste. Disposal of polymeric material by pyrolysis or catalytic cracking yields valuable hydrocarbon fuels or monomers. Literature reports different types of reactors and arrangements that have uniform temperatures during pyrolysis and catalytic cracking. The present study focuses on reducing the temperature to maximize the quantity of styrene monomer in the liquid product. A bench scale reactor has been developed to recover the styrene monomer and other valuable chemicals. Experiments were carried under partial oxidation and vacuum conditions in the temperature range of 300-500 degrees C. In the pyrolysis optimization studies, the best atmospheric condition was determined to be vacuum, the pyrolysis temperature should be 500 degrees C, yield of liquid product obtained was 91.7% and yield of styrene obtained was 85.5%. In the characterization studies, distillation and IR spectroscopy experiments were carried out. The remaining of the liquid product comprises of benzene, ethyl benzene, and styrene dimers and trimers.

Solid waste management in Abadan and Khorramshahr, Iran

Abadan and Khorramshahr are located in the south west of Iran. The aim of this study was to make an overall assessment of different functional elements of municipal solid waste management including generation, process and in-site storage, collection, transportation, treatment and recycling, and final disposal in these cities. The physical waste analysis showed that food wastes are the main component of municipal solid waste. The average proportions of food waste in the solid wastes of Abadan and Khorramshahr were 85% and 78%, respectively. Consumption of raw and unprocessed foods such as different types of vegetables and the high rate of fruit consumption are the main reasons for the high percentages of food wastes in the solid waste of these cities. At present, there is no systematic recycling and treatment of solid waste in these cities. Some people informally collect the valuable parts of municipal solid waste, such as papers, plastics and metals, in the cities and even at the disposal sites. Municipal solid wastes are collected every day and transferred to the disposal sites. The method of disposal is land treatment, which causes environmental pollution in the region. According to the results of the present study, the recycling of municipal solid waste components at source and converting the food wastes to compost are the best methods for municipal solid waste management in these cities. The construction of a composting plant with a capacity of 250 t of municipal solid waste per day is suggested for both cities. The final compost can be used as a soil conditioner for applications in agriculture or on local farms.

Aerobic digestion of municipal solid waste in Durham, UK

An in-vessel aerobic digestion plant has been in operation at the Thornley waste transfer station in County Durham, UK, since January 2002. Until recently the plant consisted of two aerobic digestion towers with a total capacity in excess of 30 000 t per annum; it processes unsegregated municipal solid waste (MSW) resulting in a diversion rate of over 70% of its input weight from landfill. This type of process is commonly referred to as mechanical and biological treatment (MBT) and is attracting significant interest from local authorities as an alternative to mass burn incineration and landfill disposal. In contrast to some other MBT systems, this system is configured to optimise conditions for maximum degradation of the biodegradable components of MSW commonly referred to as biodegradable municipal waste (BMW). While the current plant has been in operation for 4·5 years, assistance was sought from the UK Department for Environment, Food and Rural Affairs under the New Technologies Demonstrator Programme to support additional research and development with the aim of enhancing the process.

Resource recovery potential from secondary components of segregated municipal solid wastes

Fermentable components of municipal solid wastes (MSW) such as fruit and vegetable wastes (FVW), leaf litter, paddy straw, cane bagasse, cane trash and paper are generated in large quantities at various pockets of the city. These form potential feedstocks for decentralized biogas plants to be operated in the vicinity. We characterized the fermentation potential of six of the above MSW fractions for their suitability to be converted to biogas and anaerobic compost using the solid-state stratified bed (SSB) process in a laboratory study. FVW and leaf litter (paper mulberry leaves) decomposed almost completely while paddy straw, sugarcane trash, sugarcane bagasse and photocopying paper decomposed to a lower extent. In the SSB process between 50-60% of the biological methane potential (BMP) could be realized. Observations revealed that the SSB process needs to be adapted differently for each of the feedstocks to obtain a higher gas recovery. Bagasse produced the largest fraction of anaerobic compost (fermentation residue) and has the potential for reuse in many ways.

Non-Composted Municipal Solid Waste Processing Byproduct Effect on Soil Reclamation

ABSTRACT A new garbage processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. The non-composted byproduct of this process, Fluff®, has the potential to be utilized as a soil amendment to improve soil conditions in highly degraded soils. A study was initiated to evaluate Fluff as a soil amendment for establishing native grasses on disturbed US Army training lands. The Fluff was incorporated into a sandy loam soil at Fort Benning Military Reservation, GA on two sites: a moderately degraded and a highly degraded soil. The Fluff was incorporated at rates of 0, 18, 36, 72, and 143 Mg ha− 1 to assess the effects on soil properties for two growing seasons. The addition of Fluff improved available plant nutrients and soil pH levels at both sites. Also, Fluff reduced the level of soil bulk density and increased soil concentration of carbon (C) and nitrogen (N). Because no adverse environmental effects were detected and Fluff improved soil physical and nutrient conditions as well as improving perennial grass establishment with increasing application rates, land application of Fluff to degraded US Army training grounds could be considered a viable and beneficial alternative to current waste management practices.

SO2 emission characteristics and BP neural networks prediction in MSW/coal co-fired fluidized beds

The HCl emission characteristics of typical municipal solid waste (MSW) components and their mixtures have been investigated in a phi 150 mm fluidized bed. Some influencing factors of HCl emission in MSW fluidized bed incinerator was found in this study. The HCl emission is increasing with the growth of bed temperature, while it is decreasing with the increment of oxygen concentration at furnace exit. When the weight percentage of auxiliary coal is increased, the conversion rate of Cl to HCl is increasing. The HCl emission is decreased, if the sorbent (CaO) is added during the incineration process. Based on these experimental results, a 14 x 6 x 1 three-layer BP neural networks prediction model of HCl emission in MSW/coal co-fired fluidized bed incinerator was built. The numbers of input nodes and hidden nodes were fixed on by canonical correlation analysis technique and dynamic construction method respectively. The prediction results of this model gave good agreement with the experimental results, which indicates that the model has relatively high accuracy and good generalization ability. It was found that BP neural network is an effectual method used to predict the HCl emission of MSW/coal co-fired fluidized bed incinerator.

Release of Trace Organic Compounds during the Decomposition of Municipal Solid Waste Components

Landfill gas contains numerous speciated organic compounds (SOCs) including alkanes, aromatics, chlorinated aliphatic hydrocarbons, alcohols, ketones, terpenes, chlorofluoro compounds, and siloxanes. The source, rate and extent of release of these compounds are poorly understood. The objective of this study was to characterize the release of SOCs and the regulated parameter, non-methane organic compounds (NMOCs) during the decomposition of residential refuse and its major biodegradable components [paper (P), yard waste (YW), food waste (FW)]. Work was conducted under anaerobic conditions in 8-L reactors operated to maximize decomposition. Refuse and YW were also tested under aerobic conditions. NMOC release during anaerobic decomposition of refuse, P, YW, and FW was 0.151, 0.016, 0.038, and 0.221 mg-C dry g(-1), respectively, while release during aerobic decomposition of refuse and YW was 0.282 and 0.236 mg-C dry g(-1), respectively. The highest NMOC release was measured under abiotic conditions (3.01 mg-C dry g(-1)), suggesting the importance of gas stripping. NMOC release was faster than CH4 production in all treatments. Terpenes and ketones accounted for 32-96% of SOC release in each treatment, while volatile fatty acids were not a significant contributor. Release in aerobic systems points to the potential importance of composting plants as an emissions source.

Effects of an Uncomposted Municipal Waste Processing By‐Product on Prairie Grass Establishment

A garbage processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. A study was initiated to evaluate the uncomposted organic by‐product of this process as a soil amendment for establishing native prairie grasses on disturbed Army training lands. The waste was incorporated into sandy soils at Fort Benning Military Reservation on two sites: a moderately degraded and a highly degraded soil. The waste material was applied at rates of 0, 17.9, 35.8, 71.6, and 143 Mg ha−1 and seeded with native prairie grasses to assess its effects on vegetation for two growing seasons, with an additional unseeded control treatment for comparison to natural recovery. The addition of uncomposted waste increased percent composition and basal cover of switchgrass (Panicum virgatum L.) at both sites and percent composition of big bluestem (Andropogon gerardii Vitman) at one site. Indiangrass [Sorghastrum nutans (L.) Nash] was negatively affected by the addition of the waste material at both sites. Biomass in the 143 Mg ha−1 treatment increased 4180% compared to the seeded control at the highly degraded site. Plant uptake of P and Na increased at both sites and an apparent Fe toxicity problem was alleviated at the highly disturbed site with increasing application rates. Because perennial grass establishment improved so dramatically with increasing application rates, land application of this uncomposted waste material could be considered a viable and beneficial alternative to current waste management practices for degraded Army lands.

Recycling building demolition waste in hot-mix asphalt concrete: a case study in Kuwait

Building demolition waste constitutes a major component of municipal solid waste in Kuwait. Over 90% of this waste is currently land-filled, causing extreme pressure on the available land-fill sites. At the same time, the sources of natural aggregates are almost depleted, and there is an increasing demand because of the increased construction and maintenance activities. This article presents the results of a technical feasibility study into meeting this need by recycling the aggregates obtained from building demolition waste for asphalt concrete. The Marshall test, the immersion compression test, the loss of stability test, and the wheel track test were performed to evaluate the asphalt concrete made with recycled aggregate. The results showed that the asphalt concrete produced using an aggregate of demolition waste met all the requirements of local specifications.

A kinetic analysis of solid waste composting at optimal conditions

Six municipal solid waste (MSW) and yard waste components (food waste, mixed paper, yard waste, leaves, branches, grass clippings) were aerobically decomposed to measure the extent of decomposition under near optimal conditions. Decomposition was characterized by at least two principal stages, for most components, as was indicated by the carbon dioxide production rates. An aerobic biodegradation conceptual model is presented here based on the principle that solids hydrolysis is the rate-limiting step during solid waste composting. The mineralizable solid carbon of each solid waste component was assumed to comprise the readily, the moderately and the slowly (or refractory) hydrolysable carbons, each hydrolyzing at different rates to aqueous (water soluble) carbon. Aqueous carbon mineralizes to CO 2 at rapid rates that are not rate-limiting to the process. Solids hydrolysis rate constants were calculated after fitting the experimentally determined carbon dioxide production rate data to model results. Hydrolysis rates for the readily hydrolysable carbon in all components ranged from approximately 0.06 to 0.1 d −1; hydrolysis rates for the moderately hydrolysable carbon ranged from 0.005 to 0.06 d −1. Leaves, branches and grass clippings did not have a readily hydrolysable carbon fraction, whilst the leaves and branches had the largest slowly hydrolysable carbon fractions (70%, 82%, respectively, of the total solid organic carbon). Grass and yard waste did not contain slowly hydrolysable carbon fractions. Food waste had the largest readily hydrolysable carbon fraction and produced the highest amount of CO 2 among all substrates. Moderately hydrolysable solid carbon fractions ranged from 16% to 90% of the total solid organic carbon for all substrates used.

The Pyrolysis Characteristics of Each Component in Municipal Solid Waste and Thermal Degradation of Its Gases

In order to develop a gasifier of municipal solid waste (MSW), the basic characteristics of pyrolysis and thermal degradation of its gases derived from each component of MSW were examined. Tea leaf, cotton, paper, wood and fish meat decomposed rapidly in the temperature range of 550–650 K. For PE, PP and PS, the maximum rate of weight loss occurred in the temperature range of 600–750 K. For PVC, on the other hand, there existed two distinct steps of weight loss, which represented a lower (550–620 K) and a higher temperature (700–770 K) of decomposition.The gases derived in pyrolysis process at 770 K were further degraded during thermal degradation at 1020–1220 K for 5–15 s. Comparing between the amount of resultant tar before degradation at 1220 K for 15 s and after, average content of tar with molar fraction of 0.36 reduces to 0.03.

Emission of volatile organic compounds during composting of municipal solid wastes

The objective of this study was to identify and quantify volatile and semi-volatile organic compounds (VOCs) produced during composting of the organic fraction of municipal solid wastes (MSW). A laboratory experiment was conducted using organic components of MSW that were decomposed under controlled aerobic conditions. Mixed paper primarily produced alkylated benzenes, alcohols and alkanes. Yard wastes primarily produced terpenes, alkylated benzenes, ketones and alkanes, while food wastes primarily produced sulfides, acids and alcohols. Among 13 aromatic VOCs found in MSW composting facilities, toluene, ethylbenzene, 1,4-dichlorobenzene, p-isopropyl toluene, and naphthalene were in the largest amounts. Unseeded mixed paper, seeded mixed paper, seeded yard wastes, unseeded yard wastes, seeded food wastes and unseeded food wastes produced approximately 6.5, 6.1, 2.1, 0.83, 2.5 and 0.33 mg of 13 volatile and semi-volatile aromatic organic compounds combined, respectively, per dry kg. All VOCs were emitted early during the composting process and their production rates decreased with time at thermophilic temperatures.

Technical, economic and environmental analysis of energy production from municipal solid waste

Four technologies are investigated which produce energy from municipal solid waste (MSW): incineration, gasification, generation of biogas and utilisation in a combined heat and power (CHP) plant, generation of biogas and conversion to transport fuel. Typically the residual component of MSW (non-recyclable, non-organic) is incinerated producing electricity at an efficiency of about 20% and thermal product at an efficiency of about 55%. This is problematic in an Irish context where utilisation of thermal products is not the norm. Gasification produces electricity at an efficiency of about 34%; this would suggest that gasification of the residual component of MSW is more advantageous than incineration where a market for thermal product does not exist. Gasification produces more electricity than incineration, requires a smaller gate fee than incineration and when thermal product is not utilised generates less greenhouse gas per kWh than incineration. Gasification of MSW (a non-homogenous fuel) is, however, not proven at commercial scale. Biogas may be generated by digesting the organic fraction of MSW (OFMSW). The produced biogas may be utilised for CHP production or for transport fuel production as CH 4-enriched biogas. When used to produce transport fuel some of the biogas is used in a small CHP unit to meet electricity demand on site. This generates a surplus thermal product. Both biogas technologies require significantly less investment costs than the thermal conversion technologies (incineration and gasification) and have smaller gate fees. Of the four technologies investigated transport fuel production requires the least gate fee. A shortfall of the transport fuel production technology is that only 50% of biogas is available for scrubbing to CH 4-enriched biogas.

Combustible and incombustible speciation of Cl and S in various components of municipal solid waste

Chlorine (Cl) and sulfur (S) in municipal solid waste (MSW) are important reactive elements during combustion. They generate the acidic pollutants HCl and SO x , and, furthermore, produce and suppress organic chlorinated compounds. Nevertheless, few practical reports about Cl and S content in MSW have been published. In combustion and recycling processes, both combustible Cl and S, and incombustible Cl and S species are equally important. This paper presents the results of a comprehensive study about combustible and incombustible Cl and S in MSW components, including kitchen garbage, paper, textiles, wood and leaves, plastics and small chips. By integrating this collected data with data about MSW composition, not only the overall content of Cl and S in MSW, but also the origins of both combustible and incombustible Cl and S were estimated. The average Cl content in bulk MSW was 3.7 g/kg of raw MSW, of which 2.7 and 1.0 g/kg were combustible and incombustible, respectively. The Cl contribution from plastics was 76% and 27% with respect to combustible and incombustible states. The average S content in bulk MSW was 0.81 g/kg of raw MSW, of which 0.46 g/kg was combustible and 0.35 g/kg was incombustible. Combustible S was mainly due to synthetic textiles, while incombustible S was primarily from paper.

Energy potential from municipal solid waste in Malaysia

The average amount of municipal solid waste (MSW) generated in Malaysia is 0.5–0.8 kg/person/day and has increased to 1.7 kg/person/day in major cities. This paper highlights the MSW characteristics for the city of Kuala Lumpur. Currently, the waste management approach being employed is landfill, but due to rapid development and lack of space for new landfills, big cities in Malaysia are switching to incineration. A simple evaluation was conducted to establish the amount of energy that would be recovered based on the characteristics of the MSW if it were to be incinerated. From the characterization exercise, the main components of the Malaysian MSW were found to be food, paper and plastic, which made up almost 80% of the waste by weight. The average moisture content of the MSW was about 55%, making incineration a challenging task. The calorific value of the Malaysian MSW ranged between 1500 and 2600 kcal/kg. However, the energy potential from an incineration plant operating based on 1500 ton of MSW/day with an average calorific value of 2200 kcal/kg is assessed to be at 640 kW/day.

Studies on the pyrolysis behavior of gasification and melting systems for municipal solid waste

It is important to investigate the pyrolysis processes of municipal solid waste (MSW) in the same way as for any mixture comprised of multiple substances. In this article, a two-reaction model for a variety of MSW mixtures is proposed to predict mass changes due to pyrolysis. In order to formulate the model based on pyrolysis kinetics, we conducted experiments to determine the kinetic model parameters. By thermal analysis of the typical components of MSW, mass changes attributable to the pyrolysis reaction were found at about 350°C for paper, 400°–500°C for plastics, and 200°–400°C for garbage (dry condition). Activation energies were obtained by the Ozawa method based on the mass changes in pyrolysis. Thus, the pyrolysis behavior is formulated as a function of temperature. Then the pyrolysis mass change of the mixture can be predicted by using a weighted sum of the individual components. The model proved useful in experiments with real waste (refuse-derived fuels). Furthermore, the weight yields (pyrolysis gas, tars, solid residues) of the mixture can be calculated by their additive property after measuring the mass balance of each component.

Axial transport and residence time of MSW in rotary kilns: Part I. Experimental

Experiments on the influences of operational variables on the axial transport of both heterogeneous municipal solid waste (MSW) and homogenous sand are conducted in a continuous lab-scale rotary kiln cold simulator. Compared with sand, the residence time of MSW has a relatively large discrepancy with the ideal normal distribution due to the trajectory segregation of MSW components. The residence time at different axial zone is quite different due to the varied bed depth profile along the kiln length. MSW has a longer mean residence time (MRT) and a lower material volumetric flow (MVF) than sand because of the higher θ d than sand. The increment of both rotating speed and kiln slope reduces MRT, and increases MVF. Exit dam has a significant impact on the MRT and the influence of internal structure group consisting of various axial ribs and circular ribs is mainly determined by the height of circular ribs. Inside wall roughness also has effect on MRT through changing the bed regimes. For a case with the certain inlet and exit bed depths, the product of MRT and MVF holds at a constant within the limits of experimental errors in spite of the changing experimental variables.

Study on mixing performance of municipal solid waste (MSW) in differential density fluidized beds (FBs)

Mixing performances of municipal solid waste (MSW) in differential density fluidized beds (FBs) have been investigated simulating five kinds of materials (plastic, wood, candle, coal and coal-stone). The results show that the differential density FB technology can realize good mixing performances for different MSW components. The density of MSW components has a conspicuous effect on the mixing characteristics of FB. Also, the size of the components has effects. The mixing index is adopted via a regression analysis to the experimental data, and a mixing expression formula is obtained, that will be beneficial for MSW incinerator design and operation.

Pyrolysis characteristics and kinetics of municipal solid wastes

The large variety in municipal solid waste (MSW) composition and differences in thermal degradation behaviour of MSW components makes modelling, design and operation of thermal conversion systems a challenge. The pyrolysis characteristics of 11 different components, representing the dry cellulosic fraction and plastics of MSW, have been investigated. The aim of this study is to obtain detailed information on the pyrolysis characteristics and chemical kinetics of the most important components in MSW. A thermogravimetric analysis including determination of kinetic parameters are performed at a constant heating rate of 10°C/min in an inert atmosphere. The cellulosic fraction of MSW was modelled by three independent parallel reactions describing the degradation of hemicellulose, cellulose and lignin. The plastics polystyrene, polypropylene, low-density polyethylene and high-density polyethylene were all modelled as single reactions describing the degradation of hydrocarbon polymers. The degradation of PVC was modelled with three parallel reactions describing the release of benzene during dehydrochlorination, dehydrochlorination reaction and degradation of remaining hydrocarbons. Possible interactions between different paper and plastic components in mixtures were also investigated. It was found that the reactivity of cellulosic matter was increased in a mixture with PVC.

Methane Emissions from Domestic Waste Management Facilities in Jordan—Applicability of IPCC Methodology

ABSTRACT In this paper, methane emissions from municipal wastewater treatment plants and municipal solid waste (MSW) landfills in Jordan for 1994 have been estimated using the methodology developed by the Intergovernmental Panel on Climate Change (IPCC). For this purpose, the 14 domestic wastewater treatment plants in the country were surveyed. Generation rates and characterization of MSW components as well as dumping and landfilling practices were surveyed in order to estimate 1994 CH4 emissions from these sites. Locally available waste statistics were used in cases where those of the IPCC guidelines were not representative of Jordan's statistics. Methane emissions from domestic wastewater in Jordan were estimated at 4.66 gigagrams (Gg). Total 1994 CH4 emissions from MSW management facilities in Jordan are estimated at 371.76 Gg—351.12 Gg (94.45%) from sanitary landfills, 19.83 Gg (5.33%) from MSW open dumps, and 0.81 Gg (0.22%) from raw sewage-water dumping ponds. Uncertainties associated with these estimations are presented.