Mixed Municipal Solid Waste Research Articles

Sewage sludge, compost and other representative organic wastes as agricultural soil amendments: Benefits versus limiting factors

Nine different samples of sewage sludges, composts and other representative organic wastes, with potential interest to be used as agricultural soil amendments, were characterized: municipal sewage sludge (SS1 and SS2), agro industrial sludge (AIS), municipal slaughterhouse sludge (MSS), mixed municipal solid waste compost (MMSWC), agricultural wastes compost (AWC), compost produced from agricultural wastes and sewage sludge (AWSSC), pig slurry digestate (PSD) and paper mill wastes (PMW). The characterization was made considering their: (i) physicochemical parameters, (ii) total and bioavailable heavy metals (Cd, Cr, Cu, Ni, Pb, Zn and Hg), (iii) organic contaminants, (iv) pathogenic microorganisms and (v) stability and phytotoxicity indicators. All the sludges, municipal or other, comply with the requirements of the legislation regarding the possibility of their application to agricultural soil (with the exception of SS2, due to its pathogenic microorganisms content), with a content of organic matter and nutrients that make them interesting to be applied to soil. The composts presented, in general, some constraints regarding their application to soil, and their impairment was due to the existence of heavy metal concentrations exceeding the proposed limit of the draft European legislation. As a consequence, with the exception of AWSSC, most compost samples were not able to meet these quality criteria, which are more conservative for compost than for sewage sludge. From the results, the composting of sewage sludge is recommended as a way to turn a less stabilized waste into a material that is no longer classified as a waste and, judging by the results of this work, with lower heavy metal content than the other composted materials, and without sanitation problems.

Environmental impacts of a large-scale incinerator with mixed MSW of high water content from a LCA perspective

Large-scale incinerators are applied widely as a result of the heavy burden of municipal solid waste (MSW) generated, while strong opposition is arising from the public living nearby. A large-scale working incineration plant of 1500ton/day was chosen for evaluation using life cycle assessment. It was found that the corresponding human toxicity impacts via soil (HTs), human toxicity impacts via water (HTw) and human toxicity impacts via air (HTa) categories are 0.213, 2.171, and 0.012 personal equivalents (PE), and global warming (GW100) and nutrient enrichment (NE) impacts are 0.002 and 0.001 PE per ton of waste burned for this plant. Heavy metals in flue gas, such as Hg and Pb, are the two dominant contributors to the toxicity impact categories, and energy recovery could reduce the GW100 and NE greatly. The corresponding HTs, HTw and HTa decrease to 0.087, 0.911 and 0.008 PE, and GW100 turns into savings of −0.007 PE due to the increase of the heating value from 3935 to 5811kJ/kg, if a trommel screener of 40mmmesh size is used to pre-separate MSW. MSW sorting and the reduction of water content by physical pressure might be two promising pre-treatment methods to improve the combustion performance, and the application of stricter standards for leachate discharge and the flue gas purification process are two critical factors for improvement of the environmental profile identified in this work.

The contribution of biowaste disposal to odor emission from landfills

The biowaste fractions in municipal solid waste (MSW) are the main odor sources in landfill and cause widespread complaints from residents. The ammonia (NH3) and hydrogen sulfide (H2S) generation processes were simulated and compared between four typical biowaste fractions individually and combined in the mixed MSW. Food waste was found to be the main contributor to odor emission in mixed MSW, with H2S generation potential of 48.4 μg kg−1 and NH3 generation potential of 4742 μg kg−1. Fruit waste was another source for NH3 generation, with 3933 μg kg−1 NH3 generation potential. Meanwhile, nitrogen (N) was released in a faster way than sulfur (S) in waste, since 31% and 46% of total NH3 and H2S were generated in the first 90 days after disposal, with 1811 and 72 μg kg−1, and more emphasis should be placed in this initial period.Implications: Monitoring of odor generation from biowastes in MSW on a laboratory scale showed that food waste is the main source for NH3 and H2S generation, whereas waste fruit is another main contributor for NH3 released. Generally, N was released in a faster way than S from mixed-waste landfilling.

Assessment of the microbiological contamination of air in a municipal solid waste treatment company

The subject of the study is the analysis of the number of microorganisms forming a microbiological aerosol in a municipal solid waste treatment plant in Krakow. The storage time of mixed municipal solid waste in the plant hall is 6–48 hours and the storage time of the produced alternative fuel is within the range of 12–96 hours. 18 employees work in the three shift system in the sorting facility. The air for research was sampled using a MAS-100 impactor (Merck, Switzerland) in three locations within the plant, four times within a year to assess the effect of meteorological conditions (temperature, humidity and dustiness) on the number of selected groups of microorganisms. It was found that the number of microorganisms changes with seasons and depends on the meteorological conditions as well as the air sampling location. Since the border values of bioaerosol concentration were exceeded, further research is required to assess the changes in the number of microorganisms with potential negative impact on human health.

Future of organic farming in sustainable agriculture

This article provides information about composting-key ingredient in organic farming which plays a vital role in sustainable agriculture. Organic waste material including livestock waste, food waste, garden waste, waste paper and mixed municipal solid waste representing major fraction of our waste stream, are common raw materials used for compost production. Organic material is collected and decomposed together. Various physical, chemical and biological components are involved in the production of compost. Vermi-composting, aerobic composting and anaerobic composting are the three types of composting. Vermi-composting is used to decompose food material using microorganisms and insects. It is a nutrient rich organic fertilizer and soil conditioner. Aerobic composting uses oxygen to biologically decompose waste material in controlled conditions. Anaerobic composting is done through fermentation using no or limited oxygen. Anaerobic microbes decompose the waste material. Composting is beneficial for both soil and environment. It is a substitute for chemical fertilizer and also increases fertility of the soil. It increases water utilization capacity of soil and is drought resistance. It helps to reduce amount of waste and prevent from environment pollution. Methane gas produced in anaerobic composting is used as source of energy production. Composting is a method of today that will affect our ecology positively tomorrow.

Influence of Aeration Modes on Aerobic Bio-Drying of Municipal Solid Waste (MSW)

The process of biodrying could be a good solution for municipal solid waste management, allowing the production of fuel with an interesting energy content. In this study, bio-drying the mixed municipal solid waste (with the size among 15-80 mm) with different aeration modes were conducted. During the experiment, temperature, oxygen content and moisture content were determined, and continuous measurements of H2S and CH4 were taken. The results indicated that the thermophilic phases of all treatments beside T1 were met the Chinese standard of >55°C for 5-7 days for sanitation. The aeration mode of T4 was in favor of reduced the H2S and CH4 emission during MSW bio-drying. Under the condition of this study, the bio-drying cycle should be determined for 18 days. Intermittent ventilation mode is more effective to reduce the moisture content in MSW bio-drying process. So the aeration mode of T4 (2.0L/min, 30min run/30 min stop) was the first choice during MSW bio-drying.

Characterization of Nitrogen during a Short-Term Biological Pretreatment of MSW

Biological pretreatment of municipal solid wastes (MSW) has been proved to be a practice capable of reducing the ammoniacal nitrogen content in the leachate. In this study the transformations of nitrogen were investigated during a short-term biological pretreatment of mixed MSW by using static pile composting. The performance of a large-scale biological treatment process had been studied on about 100 tons of raw municipal solid waste for 16 days. MSW samples were collected at different stages of the process and analyzed to investigate the evolution of nitrogen forms. The results indicate that the ammoniacal nitrogen concentration increased during the first 3 days and decreased subsequently. Ammonia volatilization likely contribute to the reduction of the ammoniacal nitrogen content assessed. The total nitrogen content reduce from 5.5g/kg to 2.1g/kg and the production of nitrites and nitrates is negligible during pretreatment. This data indicate that 16 days of static pile composting with low aeration would be sufficient.

Recovery of glass contained in the heavy residual fraction of Portuguese mechanical Biological Treatment Plants

Abstract The aim of this work is the valorisation of the heavy residual fraction of Mechanical Biological Treatment (MBT) plants fed with mixed Municipal Solid Waste. This product contains a significant amount of glass. In the present work, it was found that the glass content in this product varies from plant to plant. Minimum and maximum values of 33 and 67% were determined. This material is not recycled today, being instead landfilled, because the contamination with other materials is so high that is not possible to process it by optical sorting, which is the end-of-line technology used in glass recycling. Nevertheless, it is possible to upgrade this product by removing a significant percentage of the stones, the main inert contaminant, with a simple and cheap process, RecGlass, which exploits the differences in the shape of glass particles and stones. This paper presents the results of a study carried out with samples of 5 Portuguese MBT plants of different characteristics. The fraction

Heavy metal leaching and environmental risk from the use of compost-like output as an energy crop growth substrate

Conversion of productive agricultural land towards growth of energy crops has become increasingly controversial. Closed landfill sites represent significant areas of brownfield land, which have potential for the establishment of energy crops. Increasingly composts are now being produced from the degradable fraction of mixed municipal solid waste (MSW) and are commonly referred to as Compost-Like-Output (CLO). However, leaching of heavy metal and other elements due to the use of CLO as soil amendment has the potential to pose a risk to the wider environment as a diffuse pollution source if not managed correctly. Salix viminalis and Eucalyptus nitens were grown at 5 different CLO application rates (equivalent to 250, 1000, 3000, 6000, 10000kgN/Ha) with weekly leachate analysis to assess the solubility of heavy metals and the potential release into the environment. The change in plant total dry mass suggested 3000kgN/Ha as the optimum application rate for both species. Weekly leachate analysis identified excess soluble ions within the first 4weeks, with heavy metals concentrations exceeding water quality limits at the higher application rates (>3000kgN/Ha). Heavy metal uptake and accumulation within each species was also investigated; S. viminalis accumulated greater levels of heavy metals than E. nitens with a general trend of metal accumulation in root>stem>leaf material. Heavy metal leaching from soils amended with CLO has the potential to occur at neutral and slightly alkaline pH levels as a result of the high buffering capacity of CLO. The use of CLO at application rates of greater than 250kgN/Ha may be limited to sites with leachate collection and containment systems, not solely for the heavy metal leaching but also excess nitrogen leaching. Alternatively lower application rates are required but will also limit biomass production.

The potential of biogas production from municipal solid waste in a tropical climate

The objective of this study was to estimate the potential of organic municipal solid waste generated in an urban setting in a tropical climate to produce biogas. Five different categories of wastes were considered: fruit waste, food waste, yard waste, paper waste, and mixed waste. These fractions were assessed for their efficiency for biogas production in a laboratory-scale batch digester for a total period of 8weeks at a temperature of 15-30°C. During this period, fruit waste, food waste, yard waste, paper waste, and mixed waste were observed to produce 0.15, 0.17, 0.10, 0.08, and 0.15m(3) of biogas per kilogram of volatile solids, respectively. The biogas produced and caloric value of each feedstock was in the range of 1.25 × 10(-3)m(3) (17kWh)/cap/day (paper waste) to 15 × 10(-3)m(3) (170kWh)/cap/day (mixed waste). Paper waste produced the least (<1×10(-3)(<17.8kWh)/cap/day), and mixed waste produced the highest methane yield (10 × 10(-3)m(3) (178kWh)/cap/day). Thus, mixed waste was found to be more efficient than other feedstocks for biogas and methane production; this was mainly related to the better C/N ratio in mixed waste. Taking the total waste production in Jimma into account, the total mixed organic solid waste could produce 865 × 10(3)m(3) (5.4m(3)/capita) of biogas or 537 × 10(3)m(3) (3.4m(3)/capita) of methane per year. The total caloric value of methane production potential from mixed organic municipal solid waste was many times higher than the total energy requirement of the area.

The operation of cost-effective on-site process for the bio-treatment of mixed municipal solid waste in rural areas

The application of on-site waste treatment significantly reduces the need for expensive waste collection and transportation in rural areas; hence, it is considered of fundamental importance in developing countries. In this study, the effects of in-field operation of two types of mini-scale on-site solid waste treatment facilities on de-centralized communities, one using mesophilic two-phase anaerobic digestion combined with composting (TPAD, 50kg/d) and another using decentralized composting (DC, 0.6–2t/d), were investigated. Source-separated collection was applied to provide organic waste for combined process, in which the amount of waste showed significant seasonal variation. The highest collection amount was 0.18kg/capital day and 0.6kg/household day. Both sites showed good performance after operating for more than 6months, with peak waste reduction rates of 53.5% in TPAD process and 63.2% in DC process. Additionally, the windrow temperature exceeded 55°C for >5days, indicating that the composting products from both facilities were safe. These results were supported by 4days aerobic static respiration rate tests. The emissions were low enough to avoid any impact on nearby communities (distance <100m). Partial energy could be recovered by the combined process but with complicated operation. Hence, the choice of process must be considered in case separately.

Combined Municipal Solid Waste and biomass system optimization for district energy applications

Municipal Solid Waste (MSW) disposal has been a controversial issue in many countries over the past years, due to disagreement among the various stakeholders on the waste management policies and technologies to be adopted. One of the ways of treating/disposing MSW is energy recovery, as waste is considered to contain a considerable amount of bio-waste and therefore can lead to renewable energy production. The overall efficiency can be very high in the cases of co-generation or tri-generation. In this paper a model is presented, aiming to support decision makers in issues relating to Municipal Solid Waste energy recovery. The idea of using more fuel sources, including MSW and agricultural residue biomass that may exist in a rural area, is explored. The model aims at optimizing the system specifications, such as the capacity of the base-load Waste-to-Energy facility, the capacity of the peak-load biomass boiler and the location of the facility. Furthermore, it defines the quantity of each potential fuel source that should be used annually, in order to maximize the financial yield of the investment. The results of an energy tri-generation case study application at a rural area of Greece, using mixed MSW and biomass, indicate positive financial yield of investment. In addition, a sensitivity analysis is performed on the effect of the most important parameters of the model on the optimum solution, pinpointing the parameters of interest rate, investment cost and heating oil price, as those requiring the attention of the decision makers. Finally, the sensitivity analysis is enhanced by a stochastic analysis to determine the effect of the volatility of parameters on the robustness of the model and the solution obtained.

The Effect of Compost Treatments and A Plant Cover with Agrostis tenuis on the Immobilization/Mobilization of Trace Elements in a Mine-Contaminated Soil

A semi-field experiment was conducted to evaluate the use of mixed municipal solid waste compost (MMSWC) and green waste-derived compost (GWC) as immobilizing agents in aided-phytostabilization of a highly acidic soil contaminated with trace elements, with and without a plant cover of Agrostis tenuis. The compost application ratio was 50 Mg ha–1, and GWC amended soil was additionally limed and supplemented with mineral fertilizers.Both treatments had an equivalent capacity to raise soil organic matter and pH, without a significant increase in soil salinity and in pseudo-total As, Cu, Pb, and Zn concentrations, allowing the establishment of a plant cover. Effective bioavailable Cu and Zn decreased as a consequence of both compost treatments, while effective bioavailable As increased by more than twice but remained as a small fraction of its pseudo-total content. Amended soil had higher soil enzymatic activities, especially in the presence of plants.Accumulation factors for As, Cu, Pb, and Zn by A. tenuis were low, and their concentrations in the plant were lower than the maximum tolerable levels for cattle. As a consequence, the use of A. tenuis can be recommended for assisted phytostabilization of this type of mine soil, in combination with one of the compost treatments evaluated.

The composition, heating value and renewable share of the energy content of mixed municipal solid waste in Finland

For the estimation of greenhouse gas emissions from waste incineration it is essential to know the share of the renewable energy content of the combusted waste. The composition and heating value information is generally available, but the renewable energy share or heating values of different fractions of waste have rarely been determined.In this study, data from Finnish studies concerning the composition and energy content of mixed MSW were collected, new experimental data on the compositions, heating values and renewable share of energy were presented and the results were compared to the estimations concluded from earlier international studies. In the town of Lappeenranta in south-eastern Finland, the share of renewable energy ranged between 25% and 34% in the energy content tests implemented for two sample trucks. The heating values of the waste and fractions of plastic waste were high in the samples compared to the earlier studies in Finland. These high values were caused by good source separation and led to a low share of renewable energy content in the waste. The results showed that in mixed municipal solid waste the renewable share of the energy content can be significantly lower than the general assumptions (50–60%) when the source separation of organic waste, paper and cardboard is carried out successfully. The number of samples was however small for making extensive conclusions on the results concerning the heating values and renewable share of energy and additional research is needed for this purpose.

Single-Walled Carbon Nanotube Transport in Representative Municipal Solid Waste Landfill Conditions

Single-walled carbon nanotubes (SWNTs) are being used in many consumer products and devices. It is likely that as some of these products reach the end of their useful life, they will be discarded in municipal solid waste landfills. However, there has been little work evaluating the fate of nanomaterials in solid waste environments. The purpose of this study is to systematically evaluate the influence of organic matter type and concentration in landfill-relevant conditions on SWNT transport through a packed-bed of mixed municipal solid waste collectors. The influence of individual waste materials on SWNT deposition is also evaluated. Transport experiments were conducted through saturated waste-containing columns over a range of simulated leachate conditions representing both mature and young leachates. Results indicate that SWNT transport may be significant in mature waste environments, with mobility decreasing with decreasing humic acid concentration. SWNT mobility in the presence of acetic acid was inhibited, suggesting their mobility in young waste environments may be small. SWNTs also exhibited collector media-dependent transport, with greatest transport in glass and least in paper. These results represent the first study evaluating how leachate age and changes in waste composition influence potential SWNT mobility in landfills.

Municipal solid waste management and landfill site selection in Greece: irrationality versus efficiency

Municipal solid waste (MSW) collection and disposal is a major problem of urban environment in the world today. MSW management solutions have to be technologically feasible, legally and socially acceptable and environmentally and financially sustainable. European policy is pushing to a rational management of natural resources; a promising technological perspective today is waste valorization, a process that becomes possible through sorting at the source, combined with material recycling and waste-to-energy methods. On the other hand, technologies like mechanical sorting, or disposal of MSW in landfills do not really improve MSW management efficiency. Landfills should become the ultimate disposal site of a few inert residuals from MSW valorization. Despite all this, conventional landfills for disposal of mixed MSW are still being constructed, with landfill site selection being a major social problem due to the lack of public acceptance; objectivity in landfill site selection is therefore extremely important. In Greece, we find several examples of inefficient MSW management and curious landfill site selection. In this paper, we criticize environmental policy issues for MSW management in Greece and identify weak points in the criteria used for the selection of landfill sites. We conclude that there is a real need for rational MSW management based on high quality scientific input.

Influence of Sewage Sludge and Leachate on Biochemical Methane Potential of Waste Biomass

In this study, biochemical methane potential assays of mixed municipal solid wastes and other types of waste such as, cellulosic, vegetable and food wastes were performed over 60 days with two different volatile solid amendments, namely domestic sewage sludge and leachate. With sewage sludge, cumulative methane (CH4) production from cellulose, food and vegetable wastes and municipal solid wastes varied from 0.23-1.51, 0.25-0.92, 0.14-0.55 and 0.07-0.21 L/g volatile solids, respectively. With leachate, the corresponding cumulative CH4 generations were 0.93-3.50, 0.97-1.81, 0.24-1.05 and 0.10-0.57 L/g VS, respectively. The individual cumulative CH4 production data fitted very well with the modified Gompertz equation and maximum methane production rates, methane production potential and lag phase time were estimated using the SigmaPlot® 11 software and this was validated by the algorithms of the Grofit software. Results showed that cumulative methane production with leachate were twice as high as with sewage slsudge. The cumulative CH4 production after 60 days varied in the order cellulose wastes>food wastes>vegetable wastes> municipal solid wastes.

Current issues on the production and utilization of medium-calorific solid recovered fuel: a case study on SRF for the HOTDISC technology

The HOTDISC technology allows the use of Solid Recovered Fuel (SRF) of a coarse grain size in cement rotary kilns. A suitable medium-calorific SRF is produced by mechanical treatment of mixed municipal and commercial waste that was previously used in fluidized bed incineration systems. Through a modification of the production process the quality of the SRF could be improved and its energetic utilization within a cement kiln with an integrated HOTDISC technology was realized. In course of a material flow analysis changes in quality and mass due to planned process changes were simulated on a theoretical basis. Due to a good agreement of the mass and quality prediction with the real data of the material flow analysis conducted after the system implementation it can be stated that by simulation beforehand the security in planning increases while the economic risk can be significantly reduced. Both the material flow analysis as well as practical operational experience confirms that the industrially produced HOTDISC SRF is applicable and can be produced from mixed municipal and commercial solid waste. An improvement in quality of the produced HOTDISC SRF can be shown by positive changes of essential parameters. From a waste management perspective the production and energetic utilization of HOTDISC SRF is reasonable by all means. This is shown by the conduction of an energy and CO₂-balance. A growing international importance of the HOTDISC technology and the increased use of medium-calorific SRF are expected.

Possible interactions between recirculated landfill leachate and the stabilized organic fraction of municipal solid waste

The stabilized organic fraction of municipal solid waste (SOFMSW) is a product of the mechanical/biological treatment (MBT) of mixed municipal solid waste (MMSW). SOFMSW is considered a 'grey' compost and the presence of pollutants (particularly heavy metals) and residual glass and plastic normally prevents agricultural use, making landfills the typical final destination for SOFMSW. Recirculation of leachate in landfills can be a cost-effective management option, but the long-term sustainability of such a practice must be verified. Column tests were carried out to examine the effect of SOFMSW on leachate recirculation. The results indicate that organic matter may be biologically degraded and metals (copper and zinc) are effectively entrapped through a combination of physical (adsorption), biological (bacterial sulfate reduction), and chemical (precipitation of metal sulfides) processes, while other chemicals (i.e. ammonia nitrogen and chloride) are essentially unaffected by filtration through SOFMSW.

Performance of a commercial-scale DiCOM™ demonstration facility treating mixed municipal solid waste in comparison with laboratory-scale data

The current paper describes the performance of a commercial-scale (20,000tpa) demonstration facility of the DiCOM™ process, a biological treatment for the organic fraction of municipal solid waste (OFMSW). The 21-d process combines aerobic composting and high-solids (30%DM), thermophilic (55°C) anaerobic digestion (AD), within a single vessel. Mechanically sorted OFMSW, derived from mixed household MSW (324t), was exposed to sequential aerobic/anaerobic/aerobic treatment. The AD, initiated by adding anaerobic inoculum from a previous trial, was stable (without pH intervention) and the onset of methanogenesis, rapid (<3h). Volatile fatty acids formed during AD (including propionate) were exhausted prior to reuse of the inoculum. As measured by an electron flux from solids to gaseous end-products, AD accounted for the greatest portion of solids degradation (86%=160m3CH4/drytOFMSW). However, unlike laboratory trials, limited degradation occurred during initial aerobic treatment. The discharged solids were classified as a composted soil conditioner.