Refuse Composition Research Articles

Image capturing, segmentation and data analysis of shredded refuse streams.

Refuse sorting is an important cornerstone of the recycling industry, but ever-changing refuse compositions and the desire to increase recycling rates still pose many unsolved challenges. The digitalisation of refuse sorting plants promises to overcome these challenges by optimising and automatically adapting the sorting process. This publication describes a system for image capturing, segmentation-based refuse recognition and data analysis of shredded refuse streams. The image capturing collects multispectral 2D and 3D images of the refuse streams on conveyor belts. The image recognition performs a semantic segmentation of the images to determine the refuse composition from the 2D images, whereas the 3D images approximate the volumes on the conveyor belts. The semantic segmentation is done by a combined convolutional neural network model, consisting of a foreground-background and a refuse class segmentation. Both models rely on synthetic training data to reduce the necessary amount of manually labelled training data, whereas the final segmentation performance reaches an Intersection over Union of up to 75%. The results of the semantic segmentation and volume estimation are combined with data of the shredding machinery by transforming it into a unified representation. This combined dataset is the basis for estimating the processed refuse masses from the semantic segmentation and volume estimation.

Evaluating the physicochemical properties of refuse with a short-term landfill age and odorous pollutants emission during landfill mining: A case study

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.

Characterization of Refuse Derived Fuel Production from Municipal Solid Waste: The Case Studies in Latvia and Lithuania

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.

Seasonal variations of geochemical parameters for a tropical landfill: Implications for landfill stabilization

Landfills stabilization stages depend on parameters such as the age of the landfill, the refuse composition, and the confinement level of the buried material. In the absence of free oxygen, redox reactions (e.g., SO42−, NO3−) and methanogenesis control the decomposition of organic matter. Landfill's stabilization stage is usually assessed by parameters such as pH, biochemical oxygen demand, chemical oxygen demand, dissolved organic carbon, and biogas composition. This study evaluates the stabilization stage of a 50-year-old tropical landfill located in Central Brazil based on physicochemical parameters, dissolved carbon isotope data (δ13C), redox reactions, and concentration of released gases CO2 and CH4. We show that seasonal variations of these parameters are modified by rainwater inflow, which carries free-oxygen into the landfill. An increase in free-oxygen leads to a13C-depletion in carbon isotopic composition of dissolved CO2 and an increase in redox-dependent species such as Fe3+, SO42−, and NO3−. Our data show that most of the landfill has reached the methanogenic stage and that periodic oxygen input by rainwater affects methane production. The studied site is a complex chemical system in which organic matter degradation occurs by aerobic, anaerobic, and methanogenic processes, depending on the recharge susceptibility.

Air quality assessment during indoor use of the tobacco heating system THS2.2

The wastes placed at a sanitary landfill contain biodegradable, nondegradable, and semidegradable matters. The biodegradable matters will be rapidly decomposed chemically and biologically into stabilized substances such as humus and inorganic fractions, which is referred to as aged refuse in this book. For the organic wastes, most organic carbon are converted into gases, few into leachate, and others remained as aged refuse. Higher temperature will lead to more rapid degradation and result to higher conversion of the organic carbon to biogas and lower to both solid residues and leachate. The refuse at landfill might be fully mineralized and the accumulative settlement might be over 30% of the initial height after around 22–30 years closure, and postclosure care may be stopped after 22 years, while chemical oxygen demand concentrations in leachate would be reduced naturally to 300 mg/L after over 15 years. A similarity and disparity comparison for different-scale lysimeters with a refuse weight from several hundred kilograms to 10,800 tons, is made, and find that a similarity exists from viewpoint of refuse degradation mechanism and declination tendency of leachate quality and refuse composition among these varied scale lysimeter. An enough weight of waste, such as over 200 kg, should be used at lab when the landfill stabilization process is simulated. The relationships between the refuse components and composition with refuse age are explored in detail and found that the wastes can be considered to be stabilized and become recyclable aged refuse after 8–10 years of placement in China. The air quality at the aged refuse mining point is acceptable and only total bacteria and PM10 may be over the control values. Microbial communities in aged refuse are much more complex than expected. Most of the predominant bacteria in aged refuse exhibit high identity to some extremophiles found in extreme conditions such as highly alkaline and/or saline environments, rocks of an ancient gold mine, old sediments, hypertolerant to arsenic, cold sulfur-rich spring, and the Qinghai-Tibet Plateau permafrost region. The predominated bacilli-like bacteria coexisted with methanogenic archaea, with a rich source of extremophiles, especially alkaliphilic and/or halophilic microbes.

Long-Term Monitoring and Prediction for Settlement and Composition of Refuse in Shanghai Laogang Municipal Landfill

Parameters about composition of refuse such as mass percentage of biodegradable matter, volatile solid, organic carbon, cellulose, total sugar, and settlement were monitored and analyzed in a large-scale experimental unit. The empirical formulas between composition and refuse age were established in terms of the data obtained from the experimental unit and verified by comparing with the corresponding parameters of refuse in the closed landfill units from 1991 until 1994 in the Shanghai Laogang Municipal Landfill. Furthermore, the long-term prediction for the composition of refuse was made, and it was predicted that the half-life is 7 to 11 years for biodegradable matter, 9 to 12 years for organic carbon or volatile solid, 7 to 16 years for cellulose, and 4 to 6 years for total sugar. In addition, a mathematical model, based on the mechanism of refuse biodegradation in the landfill, was developed to simulate the relationship between the settlement and the refuse age and manifests the secondary settlement potential. The mathematical model was proved not only to be reliable but also should be accurate for predicting the settlement of the landfill. The secondary settlement, which mainly results from the slow and gradual biodegradation of refuse, is linear with respect to the exponent of refuse age. Finally, according to the settlement model and empirical biodegradation formulas, it may be predicted that, 79.4% of biodegradable matter, 92.9% of total sugar, 72.7% of volatile solid and organic carbon, and 73.1% of cellulose will be biodegraded and that 79% of the maximum secondary settlement potential will occur before the Shanghai Laogang Municipal Landfill is in a high stabilization situation, i.e., approximately 21 years after final closure.

Urban residential refuse composition and generation rates for the 20th century.

Examination of historical data shows that 3.5 x 10(8) tonnes (t) of residential refuse was discarded in New York City (NYC) during the 20th century. Maximum and minimum rates of per capita mass discard of residential refuse during this time are reported in 1940 (940 kg per capita yr(-1)) and 1961, 1963 (320 kg per capita yr(-1)), respectively. Since 1980, per capita residential refuse discard rates have been steady and comparatively low (430 kg per capita yr(-1) +/- 2.5%). Fuel ash accounted for approximately 34% of residential refuse in NYC during the century. A decline of refuse bulk density (as collected) from approximately 500 to 200 kg m(-3) and an increase in refuse organic matter content from 20% to 80% (by mass) is reported between 1920 and 1990 and is due largely to mass fraction reductions forfuel ash and increases for paper and plastic. Approximately 4.9 x 10(8) t of refuse was disposed in NYC during the 20th century (including commercial and residential refuse), representing a total pool of about 8.0 x 10(7) t of organic carbon (as C) that has entered city landfills and incinerators.

A comparison of refuse attenuation in laboratory and field scale lysimeters

For this study, small and middle scale laboratory lysimeters, and a large scale field lysimeter in situ in Shanghai Refuse Landfill, with refuse weights of 187, 600 and 10,800,000 kg, respectively, were created. These lysimeters are compared in terms of leachate quality (pH, concentrations of COD, BOD and NH 3–N), refuse composition (biodegradable matter and volatile solid) and surface settlement for a monitoring period of 0–300 days. The objectives of this study were to explore both the similarities and disparities between laboratory and field scale lysimeters, and to compare degradation behaviors of refuse at the intensive reaction phase in the different scale lysimeters. Quantitative relationships of leachate quality and refuse composition with placement time show that degradation behaviors of refuse seem to depend heavily on the scales of the lysimeters and the parameters of concern, especially in the starting period of 0–6 months. However, some similarities exist between laboratory and field lysimeters after 4–6 months of placement because COD and BOD concentrations in leachate in the field lysimeter decrease regularly in a parallel pattern with those in the laboratory lysimeters. NH 3–N, volatile solid (VS) and biodegradable matter (BDM) also gradually decrease in parallel in this intensive reaction phase for all scale lysimeters as refuse ages. Though the concrete data are different among the different scale lysimeters, it may be considered that laboratory lysimeters with sufficient scale are basically applicable for a rough simulation of a real landfill, especially for illustrating the degradation pattern and mechanism. Settlement of refuse surface is roughly proportional to the initial refuse height.

Monitoring and long-term prediction of refuse compositions and settlement in large-scale landfill.

Settlement and changes in refuse composition for total sugar, raw cellulose, biological degradable matter, volatile solid, organic carbon, were monitored in a large-scale experimental landfill unit and closed landfill units at Shanghai Refuse Landfill from April 1995 through to October 1998. Mathematical simulation formulae between these parameters and refuse age were developed based on the data obtained from the experimental landfill unit and validated by data from landfill units closed in April of 1991, 1992, 1993 and 1994. Long-term predictions for these parameters for the landfill were made using these formulae. It was predicted that the refuse might be fully mineralized and the cumulative settlement might be over 30% of the initial height after around 22 to 30 years. The stabilization process and reuse approaches for landfills based on the compositions and settlement are discussed.

Comparative assessment of settlement models for municipal solid waste landfill applications

The biodegradation of organic matter in municipal solid waste (MSW) landfills increases the void ratio and weakens the structural strength of the refuse within a landfill leading to a substantial loss of volume and settlement. Development of completed landfill sites, which has become highly desirable particularly in land-limited locations, is invariably hindered by this settlement. Estimating long- term landfill settlements becomes an integral part of the plans for the final closure of a site and its ultimate reuse. The rate and magnitude of landfill settlement depend primarily on refuse composition and operational management practices which affect biodegradation and stabilization processes within landfills. Field scale experiments were conducted to measure refuse settlement rates, amongst other parameters, under different operational management practices including leachate recirculation, and addition of water, pH buffer and microbial seed. The effect of these practices on settlement rates and magnitude is evaluated. Field test data are used to calibrate mathematical models that are traditionally used in soil consolidation. The model parameters obtained can be used as guidance in simulating landfill settlement rates and correlating these rates to refuse biodegradation and stabilization processes within landfills.

Comparative assessment of settlement models for municipal solid waste landfill applications

The biodegradation of organic matter in municipal solid waste (MSW) landfills increases the void ratio and weakens the structural strength of the refuse within a landfill leading to a substantial loss of volume and settlement. Development of completed landfill sites, which has become highly desirable particularly in land-limited locations, is invariably hindered by this settlement. Estimating long-term landfill settlements becomes an integral part of the plans for the final closure of a site and its ultimate reuse. The rate and magnitude of landfill settlement depend primarily on refuse composition and operational management practices which affect biodegradation and stabilization processes within landfills. Field scale experiments were conducted to measure refuse settlement rates, amongst other parameters, under different operational management practices including leachate recirculation, and addition of water, pH buffer and microbial seed. The effect of these practices on settlement rates and magnitude is evaluated. Field test data are used to calibrate mathematical models that are traditionally used in soil consolidation. The model parameters obtained can be used as guidance in simulating landfill settlement rates and correlating these rates to refuse biodegradation and stabilization processes within landfills.

Waste Recycling through Composting in Nigeria

While some composting had been practiced on a limited basis in Nigeria 50 years ago, the practice still is largely neglected. Farmers find it more convenient to use fertilizers because of the ease of carrying, storing and applying. However, since 1986, there has been a major change in the composition of refuse in Nigeria. With greater numbers of people in the low socioeconomic groups scavenging on the refuse dumps collecting paper, metal, glass and plastics, the remaining refuse is mostly organic and ideal for making compost. Studies undertaken at the University of Ibadan reveal that once mobilized, communities can be effective in launching composting projects. Appropriate technology is favored in processing the wastes rather than extensive and, often unaffordable, mechanization.

Determination of trommel meshes for optimal separation of compostible fraction of municipal solid wastes from Florianópolis, SC, Brazil

The main obstacle to municipal waste composting is the presence of heavy metals. The present study presents a review of data on the composition of household refuse, with emphasis on the distribution of heavy metals in this waste, and shows that screening of municipal wastes can help improve the separation of the compostible fraction.

Environmental effects of landfills

In the past, landfilling involved burying municipal refuse directly or after on-site burning. Typically, little attention was given to proper siting and engineering to obviate the hazards of the generation of CH 4 and toxic leachates as wastes decomposed. Leachates were hopefully attenuated by natural processes (adsorption, precipitation, ion exchange, microbial decomposition or dilution in the unsaturated zone below landfills). Landfills slowly evolved by proper siting, design and management into efficiently operated bioreactors to produce purified CH 4 for use as a fuel, and leachates, which were treated biologically and chemically to minimize groundwater pollution. Microbial reactions in landfills are outlined. The amounts and composition of landfill gas and leachate as determined by the interaction of factors such as refuse composition, degree of compaction, temperature, moisture content, refuse age and depth are discussed. Typical inorganic and organic composition of landfill gases and leachates are presented. The potential and real environmental effects on soils, plants, groundwater, aquatic organisms and humans of disposal of municipal refuse by landfilling are reviewed. Finally, the most recent trend in constructing refuse landfills to serve as final storage reservoirs which are deliberately kept dry to minimize gas and leachate production is discussed and illustrated. Present activities in waste recycling to conserve landfill space are outlined.

Variation in the elemental composition of municipal refuse incinerator ashes with time of sampling

Due to the ever increasing quantities of solid waste, more refuse incinerators are coming on line in the United States. Toxic metals and organics in the resulting ash to be disposed and in suspended particulates that escape the stack are major deterrents to refuse incineration. Since refuse composition is highly variable with time, it was of interest to determine the extent of variation in element composition of the resulting fly ash and bottom ash with time of sampling. In the present study, the ashes were sampled at monthly intervals from the same refuse incinerator and analyzed for 38 elements using neutron activation analysis, emission spectrometry and other methods. Possible factors including refuse composition and reactions occurring during refuse incineration as they affect the elemental composition of refuse ashes are discussed.

Systems analysis of recycling in the D]strito Federal of Mexico

Abstract The paper presents a cost-benefit analysis of recycling options for the Distrito Federal (D.F.) of Mexico in 1985. A description of refuse management and recycling is provided. Refuse composition, refuse quantities and the costs of recycling are estimated. The analysis considers recycling by residents, businesses, street sweepers, collection trucks, recycling/compost plants and scavengers in dumps. Linear programming techniques are used to find the most economical combinations of recycling methods. Variations in the density of recycling centers, in population density and in the amount of refuse collected by street sweepers are considered. An analysis is extrapolated to the year 2000. The use of an integrated and quantitative analysis of a very complex problem provides recommendations which would not come from separate, detailed analyses of individual recycling options. In urban areas of the D.F., the analysis indicates that the most economical recycling results when businesses recycle their waste, when a combination of residents and street sweepers recycle resident waste, and when recycling centers are sited at a density of one center per two square kilometers.

Solid Waste Management Practices in the Eastern Province of Saudi Arabia

Solid waste management practices in the Eastern Province of Saudi Arabia are reviewed. The officials of various municipalities and agencies responsible for collecting and disposing of municipal waste were interviewed. The refuse generation rate found is in the range of 1.61–2.72 kg per capita per day. The refuse composition data indicate a high percentage of glass, metals, and wood. For storage purposes, 0.2-m3 barrels are used in residential areas and 0.75 to 1.50 m3-capacity containers are used in commerical areas. The present solid-waste collection system is labor-intensive, and a significant part of the budget is spent on collection and haul operations. The unit collection and haul cost is much higher than the unit disposal cost of refuse. The direct haul of refuse is the common practice, and the use of transfer stations has not yet been considered. It is also observed that the disposal methods used at these sites are not in line with modern techniques for refuse disposal. Landfilling and combined burning and landfilling are the common disposal methods at all the sites.

Refuse composition projections and recycling technology

MSW composition in the UK has changed significantly since detailed records were initiated in the 1930's and 1940's. While composition changes do not materially affect waste disposal by landfill and incineration, there is a potential adverse effect on the efficiency and costs of solid waste recycling operations such as RDF production. No medium- to long-term composition projections have been found, and this paper presents the first results from collation and time trend analysis of U.K. MSW compositions. S-curves are generally found to give the most acceptable correlations both in terms of goodness of fit and suitability for long-term forecasting. Refuse compositions, quantities and heating values are forecast up to 50 years ahead. In such a time period solid-waste management techniques are likely to reorientate towards recycling rather than disposal. Speculative and provocative forecasts of waste management techniques up to 100 years ahead are included to attract attention to the opportunities offered in this sector.

Performance of Electrostatic Precipitators

The large majority of municipal refuse incinerators utilize electrostatic precipitators for control of particulate emission. Precipitator performance is determined by the detailed chemical and physical properties of the fly ash and the gas in which it is suspended. Variations in the composition of the refuse burnt, of seasonal or other nature, as well as variations in the operation of the incinerator installation have a pronounced effect on precipitator exit emissions. Large temporal variations in the particulate emissions, not related to normally registered variations in refuse composition and plant operation, occur, as illustrated by measurements at a large Danish incinerator plant. Such variations, resulting from the variability of the process parameters, should be taken into account for the sizing and design of precipitators for new incinerator installations, and also when evaluating emission data from existing incinerator plants.

Recovery of materials from domestic refuse: Some considerations

In the recovery of materials from domestic refuse the important factors are: 1. (1) composition of refuse; 2. (2) quality of materials to be recovered; 3. (3) revenues for such materials; 4. (4) marketing factors (price fluctuations); 5. (5) costs of physical separation. Most of the foregoing are determined by typical national or even local circumstances. Furthermore, energy-related aspects are relevant, as shown in the case of recovery of the component paper, in connection with normal waste disposal methods (incineration, sanitary landfill). From several points of view it is clear that, in terms of priorities, the paper component deserves the principal attention when considering the recovery of materials from domestic waste.