Sampling household waste at source: lessons learnt in Gaborone.

Municipal solid waste (MSW) quantity and composition analysis is fundamental for the planning of municipal waste management services. The purpose of this paper is to report the results and experiences of sampling household waste at the source of generation in Gaborone, Botswana. The average generation rate, in kg capita(-1) day(-1), and percentages of various components of waste in Gaborone were determined using a statistically designed household sampling survey. The survey covered 47 households with different socio-economic characteristics over 21 days with 893 samples obtained. The results showed that the average waste generation rate for Gaborone was 0.33 kg capita(-1) day(-1). Contrary to common belief, the waste generation rate measured as in weight units was found not be directly related to household income. However, the packaging fractions of plastic and paper measured as volume had a direct relationship with household income. Across all income groups, the putrescible waste fraction constituted the highest proportion of the waste stream at approximately 68%. The main general conclusion is on the importance of practical considerations. As much as statistically designed sampling procedures provide a useful means of estimating the quantity and composition of household waste at source of generation, there are some practical issues that should be carefully considered during sampling to improve the accuracy and relevance of the results.     

Assessment of factors affecting household solid waste generation and its composition in Gulberg Town,Lahore, Pakistan

This paper analyzes and compares the findings of the characterization study of collected solid waste from households of three different socioeconomic groups in Lahore, Pakistan, over the four seasons, i.e. Spring (March–April, 2008), Summer (May–June, 2008), Monsoon (August–September, 2008) and Winter (December 2008 and January 2009). The generation rate of waste was 0.96 kg/cap/day for high-income, 0.73 kg/cap/day for middle and 0.67 kg/cap/day for low-income group. The average of total household solid waste (HSW) generation is 0.79 kg/cap/day (including 0.75 kg/cap/day for spring, 0.77 kg/cap/day for summer, 0.86 kg/cap/day for monsoon and 0.76 kg/cap/day. The breakdown for the major physical components of the waste shows that organic waste accounts for the largest proportion (67.46 %). The relations between waste generation rates by physical category and subcategory, in addition to factors such as socioeconomic groups (population density levels, household income and household size), seasonal variation, and daily variation (difference of HSW generation among days of a week) were also analyzed. Statistical analysis shows that there was no significant difference in overall waste generation among days of a week. A significant difference between the seasons for food waste, cardboard, PET, HDPE, other hazardous waste, battery cells, and dust and stone (p < 0.001) was found. The generation rates were found to be higher when compared to other developing countries.     

Household solid waste characteristics and management in Chittagong, Bangladesh

Solid waste management (SWM) is a multidimensional challenge faced by urban authorities, especially in developing countries like Bangladesh. We investigated per capita waste generation by residents, its composition, and the households' attitudes towards waste management at Rahman Nagar Residential Area, Chittagong, Bangladesh. The study involved a structured questionnaire and encompassed 75 households from five different socioeconomic groups (SEGs): low (LSEG), lower middle (LMSEG), middle (MSEG), upper middle (UMSEG) and high (HSEG). Wastes, collected from all of the groups of households, were segregated and weighed. Waste generation was 1.3kg/household/day and 0.25kg/person/day. Household solid waste (HSW) was comprised of nine categories of wastes with vegetable/food waste being the largest component (62%). Vegetable/food waste generation increased from the HSEG (47%) to the LSEG (88%). By weight, 66% of the waste was compostable in nature. The generation of HSW was positively correlated with family size (r(xy)=0.236, p<0.05), education level (r(xy)=0.244, p<0.05) and monthly income (r(xy)=0.671, p<0.01) of the households. Municipal authorities are usually the responsible agencies for solid waste collection and disposal, but the magnitude of the problem is well beyond the ability of any municipal government to tackle. Hence dwellers were found to take the service from the local waste management initiative. Of the respondents, an impressive 44% were willing to pay US$0.3 to US$0.4 per month to waste collectors and it is recommended that service charge be based on the volume of waste generated by households. Almost a quarter (22.7%) of the respondents preferred 12-1pm as the time period for their waste to be collected. This study adequately shows that household solid waste can be converted from burden to resource through segregation at the source, since people are aware of their role in this direction provided a mechanism to assist them in this pursuit exists and the burden is distributed according to the amount of waste generated.     

Characterization of urban solid waste in Chihuahua, Mexico

The characterization of urban solid waste generation is fundamental for adequate decision making in the management strategy of urban solid waste in a city. The objective of this study is to characterize the waste generated in the households of Chihuahua city, and to compare the results obtained in areas of the city with three different socioeconomic levels. In order to identify the different socioeconomic trends in waste generation and characterization, 560 samples of solid waste were collected during 1 week from 80 households in Chihuahua and were hand sorted and classified into 15 weighted fractions. The average waste generation in Chihuahua calculated in this study was 0.676 kg per capita per day in April 2006. The main fractions were: organic (48%), paper (16%) and plastic (12%). Results show an increased waste generation associated with the socioeconomic level. The characterization in amount and composition of urban waste is the first step needed for the successful implementation of an integral waste management system.     

Generation, storage, collection and transportation of municipal solid waste--a case study in the city of Kathmandu, capital of Nepal

Solid waste management (SWM) services have consistently failed to keep up with the vast amount of solid waste produced in urban areas. There is not currently an efficient system in place for the management, storage, collection, and transportation of solid waste. Kathmandu City, an important urban center of South Asia, is no exception. In Kathmandu Metropolitan City, solid waste generation is predicted to be 1091 m(3)/d (245 tons/day) and 1155 m(3)/d (260 tons/day) for the years 2005 and 2006, respectively. The majority (89%) of households in Kathmandu Metropolitan City are willing to segregate the organic and non-organic portions of their waste. Overall collection efficiency was 94% in 2003. An increase in waste collection occurred due to private sector involvement, the shutdown of the second transfer station near the airport due to local protest, a lack of funding to maintain trucks/equipment, a huge increase in plastic waste, and the willingness of people to separate their waste into separate bins. Despite a substantial increase in total expenditure, no additional investments were made to the existing development plan to introduce a modern disposal system due to insufficient funding. Due to the lack of a proper lining, raw solid waste from the existing dumping site comes in contact with river water directly, causing severe river contamination and deteriorating the quality of the water.     

The changing character of household waste in the Czech Republic between 1999 and 2009 as a function of home heating methods

The authors of this paper report on the changing character of household waste, in the Czech Republic between 1999 and 2009 in households differentiated by their heating methods. The data presented are the result of two projects, financed by the Czech Ministry of Environment, which were undertaken during this time period with the aim of focusing on the waste characterisation and complete analysis of the physicochemical properties of the household waste. In the Czech Republic, the composition of household waste varies significantly between different types of households based on the methods of home heating employed. For the purposes of these studies, the types of homes were divided into three categories – urban, mixed and rural. Some of the biggest differences were found in the quantities of certain subsample categories, especially fine residue (matter smaller than 20 mm), between urban households with central heating and rural households that primarily employ solid fuel such coal or wood. The use of these solid fuels increases the fraction of the finer categories because of the higher presence of ash. Heating values of the residual household waste from the three categories varied very significantly, ranging from 6.8 MJ/kg to 14.2 MJ/kg in 1999 and from 6.8 MJ/kg to 10.5 MJ/kg in 2009 depending on the type of household and season. The same factors affect moisture of residual household waste which varied from 23.2% to 33.3%. The chemical parameters also varied significantly, especially in the quantities of Tl, As, Cr, Zn, Fe and Mn, which were higher in rural households. Because knowledge about the properties of household waste, as well as its physicochemical characteristics, is very important not only for future waste management, but also for the prediction of the behaviour and influence of the waste on the environment as the country continues to streamline its legislation to the European Union’s solid waste mandates, the results of these studies were employed by the Czech Ministry of Environment to optimise the national waste management strategy.     

A survey on municipal solid waste and residents’ awareness in Da Nang city, Vietnam

A survey on solid waste generation and residents’ awareness was conducted in Da Nang city, Vietnam in 2010. We took samples from residents, hotels, restaurants, and city markets. Data reveals that each resident generates on average 0.71 kg/capita/day (3 kg/household/day). Regarding the composition, organic waste (food, flowers, leaves, grass) accounts for about 70 % of residents’ waste followed by plastics. Likewise, about 14 % of residents’ waste can be recycled. Furthermore, we find that middle income households in the suburbs have the largest waste generation with 4.9 kg/household/day. We consider that this finding is explained by their dedication to agricultural activities, such as planting fruit trees and vegetables, and gardening. Finally, we find that only about 60 % of interviewees have knowledge of how to segregate waste, however more than 90 % of them are willing to cooperate with the introduction of a waste segregation program in the city.     

Survey of composition and generation rate of household wastes in Beijing, China

It is recognized that information on both quantity and composition of residential waste is important for the effective planning of household waste handling infrastructure. In this paper, we present the results of a survey on household waste generation and composition in Beijing, China. Sample communities were selected by the integration of five indices including family population, income, age, and education. Wastes were sampled on a daily basis from 113 households in six different districts of Beijing City for ten days. The results showed that the generation rate of household wastes was 0.23 kg/pers/day. The bulk density was approximately 221 kg/m³, and the moisture content was approximately 50%. Household waste consisted of kitchen waste, paper/cardboard, plastics, textiles, metals, glass and other wastes, the proportion of each waste was approximately 69.3%, 10.3%, 9.8%, 1.3%, 0.8%, 0.6% and 2.7%, respectively. An evaluation of the relationship between daily per capita generation of household waste and socio-economic factors indicated that household size and income both showed a negative relationship with household waste generation (kg/pers/day). As for the effect of education, families with a secondary educational level produced fewer household wastes (kg/pers/day) than those with a primary or advanced educational level.     

Municipal solid waste management in Beijing City

This paper presents an overview of municipal solid waste (MSW) management in Beijing City. Beijing, the capital of China, has a land area of approximately 1368.32 km² with an urban population of about 13.33 million in 2006. Over the past three decades, MSW generation in Beijing City has increased tremendously from 1.04 million tons in 1978 to 4.134 million tons in 2006. The average generation rate of MSW in 2006 was 0.85 kg/capita/day. Food waste comprised 63.39%, followed by paper (11.07%), plastics (12.7%) and dust (5.78%). While all other wastes including tiles, textiles, glass, metals and wood accounted for less than 3%. Currently, 90% of MSW generated in Beijing is landfilled, 8% is incinerated and 2% is composted. Source separation collection, as a waste reduction method, has been carried out in a total of 2255 demonstration residential and commercial areas (covering about 4.7 million people) up to the end of 2007. Demonstration districts should be promoted over a wider range instead of demonstration communities. The capacity of transfer stations and treatment plants is an urgent problem as these sites are seriously overloaded. These problems should first be solved by constructing more sites and converting to new treatment technologies. Improvements in legislation, public education and the management of waste pickers are problematic issues which need to be addressed.     

Co-gasification of municipal solid waste and material recovery in a large-scale gasification and melting system

This study evaluates the effects of co-gasification of municipal solid waste with and without the municipal solid waste bottom ash using two large-scale commercial operation plants. From the viewpoint of operation data, there is no significant difference between municipal solid waste treatment with and without the bottom ash. The carbon conversion ratios are as high as 91.7% and 95.3%, respectively and this leads to significantly low PCDD/DFs yields via complete syngas combustion. The gross power generation efficiencies are 18.9% with the bottom ash and 23.0% without municipal solid waste bottom ash, respectively. The effects of the equivalence ratio are also evaluated. With the equivalence ratio increasing, carbon monoxide concentration is decreased, and carbon dioxide and the syngas temperature (top gas temperature) are increased. The carbon conversion ratio is also increased. These tendencies are seen in both modes.Co-gasification using the gasification and melting system (Direct Melting System) has a possibility to recover materials effectively. More than 90% of chlorine is distributed in fly ash. Low-boiling-point heavy metals, such as lead and zinc, are distributed in fly ash at rates of 95.2% and 92.0%, respectively. Most of high-boiling-point heavy metals, such as iron and copper, are distributed in metal. It is also clarified that slag is stable and contains few harmful heavy metals such as lead. Compared with the conventional waste management framework, 85% of the final landfill amount reduction is achieved by co-gasification of municipal solid waste with bottom ash and incombustible residues. These results indicate that the combined production of slag with co-gasification of municipal solid waste with the bottom ash constitutes an ideal approach to environmental conservation and resource recycling.     

Estimating the quantity of solid waste generation in Oyo, Nigeria.

The study established waste multipliers that could be used in conjunction with the population figure of a city to estimate the quantity of solid waste generation in the developing world. Oyo, a traditional city in Nigeria was the focus of the study. Two sets of data were collected. The first was the information on the socio-economic attributes of residents obtained from 648 households through questionnaires administered using a systematic random sampling technique. The second was the measurement of waste generated in 25% of the households for a week in each of the 12 months of the year. The study established that 23.3% of the residents surveyed have educational qualifications beyond secondary school, with 51.2% engaged in occupations requiring very little or no formal education and 50.9% were in the low-income group. The daily per capita solid waste generation was 0.129 kg. The highest (9.8%) and lowest (6.5%) of the annual quantities of waste were produced in October and February, respectively. Similarly, 20.2% of the weekly generation was produced on Saturday and the 10.2% produced on Thursday was the lowest. Animal dung, which accounted for 18.0%, constituted the highest component of the total solid waste generated. The study further established that the organic component of the waste generation was 75.4%. The results of the regression analysis R2 significant at 0.001 showed that income, household size, social status, occupation, education and season of the year explained 88.8% of waste generation in Oyo. It was established that 50.90 tonnes of solid waste was generated per day in the city in 2005, and the daily generation in the year 2008 is estimated to be 55.20 tonnes. The study concluded that with an average annual population growth of 13 000 people for the town, an additional 1.3 acres of land will need to be legally acquired annually, implying that 10.92-19.68 hectares ill be required as dump site(s) over the next 20-30 years.     

Impact of food waste disposers on the generation rate and characteristics of municipal solid waste

Field surveys were carried out to ascertain the reduction in the generation rate of municipal solid waste as a result of the use of food waste disposers (FWDs). The generation rate and characteristics of garbage and of the food waste ground by FWDs in households were investigated, and the effect of FWDs was discussed. In a medium-sized village, the amount of garbage collected per collection decreased from 251.2 kg to 114.7 kg as a result of FWD use. The unit loading of ground food waste was estimated to be 111 g/cap·day. In a small village, the amount of garbage collected weekly decreased from 175 kg to 112 kg. The average unit loading of ground food waste was measured and found to be 126 g/cap·day. The reduction rate of garbage varied from 25% to 39% monthly and the average reduction rate was 31% throughout the surveying period. Dramatic variations in the characteristics of the collected garbage were recognized: the ratio of food waste on a dry basis declined by more than half, the moisture content decreased to half or less, the combustible matter content increased approximately 1.7 times or more, and the lower heating value increased approximately 2.0 times or more compared to the case without FWD use.     

Composition and production rate of dental solid waste in Xanthi, Greece: variability among dentist groups

The objective of this work was to determine the composition and production rate of dental solid waste, produced by dental practices in the Prefecture of Xanthi, a multicultural area in Northeast Greece with a population of 102,000. For the study, 22 private dental practices and 1 public dental practice were selected of the 48 private and 5 public dental practices in operation. The 22 private dental practices included 16 owned by Christian Greek-born dentists, 3 by Moslem dentists and 3 by Christian dentists repatriated from the former Soviet Union. Differentiation on the basis of religion is directly related to the countries from which dentists received their training, e.g., Greece-European Union, Turkey and former Soviet Union. Thus, including the one public dental practice, 4 study groups were considered. Waste collection took place for 22 working days, from 20 May to 27 June 2002. This period was considered to be a representative one for a semi-rural area, such as Xanthi. Dentists were instructed to collect the total amount of waste they produced. A total of 260 kg dental solid waste was collected during the study period and was manually separated. Dental solid waste was classified in three main categories: (1) Infectious and potentially infectious waste, accounting for 94.7% by weight. (2) Non-infectious waste accounting for 2.0%. (3) Domestic-type waste, accounting for 3.3% by weight. The category of infectious waste is classified as hazardous and includes components containing metal (8.51%), components without metal (91.18%) and amalgam (0.33%). Using the weight data, the production rate of dental solid waste for the study period in the Prefecture of Xanthi was determined to be 513 g/practice/day and of infectious and potentially infectious waste 486 g/practice/day. The latter includes the production rate of sharps (9.8 g/practice/day), non-sharps (31.6), infectious waste without metal (443) and amalgam (1.6 g/practice/day). Since dental solid waste is currently disposed of in landfills together with the municipal solid waste, the results of the study were used to suggest an appropriate management scheme. The results were also used to compare the composition and production rates of dental solid waste produced by the 4 study groups.     

Assessment of municipal solid waste generation and recyclable materials potential in Kuala Lumpur,Malaysia

This paper presents a forecasting study of municipal solid waste generation (MSWG) rate and potential of its recyclable components in Kuala Lumpur (KL), the capital city of Malaysia. The generation rates and composition of solid wastes of various classes such as street cleansing, landscape and garden, industrial and constructional, institutional, residential and commercial are analyzed. The past and present trends are studied and extrapolated for the coming years using Microsoft office 2003 Excel spreadsheet assuming a linear behavior. The study shows that increased solid waste generation of KL is alarming. For instance, the amount of daily residential SWG is found to be about 1.62 kg/capita; with the national average at 0.8–0.9 kg/capita and is expected to be increasing linearly, reaching to 2.23 kg/capita by 2024. This figure seems reasonable for an urban developing area like KL city. It is also found that, food (organic) waste is the major recyclable component followed by mix paper and mix plastics. Along with estimated population growth and their business activities, it has been observed that the city is still lacking in terms of efficient waste treatment technology, sufficient fund, public awareness, maintaining the established norms of industrial waste treatment etc. Hence it is recommended that the concerned authority (DBKL) shall view this issue seriously.     

Characterization of air emissions and residual ash from open burning of electronic wastes during simulated rudimentary recycling operations

Air emissions and residual ash samples were collected and analyzed during experiments of open, uncontrolled combustion of electronic waste (e-waste), simulating practices associated with rudimentary e-waste recycling operations. Circuit boards and insulated wires were handled separately to simulate processes associated with metal recovery. The average emissions of polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDFs) were 92 ng toxic equivalency (TEQ)/kg [n = 2, relative standard deviation (RSD) = 98%] and 11 900 ng TEQ/kg (n = 3, RSD = 50%) of the initial mass of the circuit boards and insulated wire, respectively. The value for the insulated wire is about 100 times higher than that for backyard barrel burning of domestic waste. The emission concentrations of polybrominated dibenzodioxins and dibenzofurans (PBDD/PBDFs) from the combustion of circuit boards were 100 times higher than for their polychlorinated counterparts. Particulate matter (PM) sampling of the fly ash emissions indicated PM emission factors of approximately 15 and 17 g/kg of the initial mass for the circuit boards and insulated wire, respectively. Fly ash samples from both types of e-waste contained considerable amounts of several metallic elements and halogens; lead concentrations were more than 200 times the United States regulatory limits for municipal waste combustors and 20 times those for secondary lead smelters. Leaching tests of the residual bottom ash showed that lead concentrations exceeded U.S. Environmental Protection Agency landfill limits, designating this ash as a hazardous waste.     

Characteristics of ashes from different locations at the MSW incinerator equipped with various air pollution control devices

The characteristics of ashes from different locations at a municipal solid waste incinerator (MSWI) equipped with a water spray tower (WST) as a cooling system, and a spray dryer adsorber (SDA), a bag filter (BF) and a selective catalytic reactor (SCR) as air pollution control devices (APCD) was investigated to provide the basic data for further treatment of ashes. A commercial MSWI with a capacity of 100 tons per day was selected. Ash was sampled from different locations during the normal operation of the MSWI and was analyzed to obtain chemical composition, basicity, metal contents and leaching behavior of heavy metals. Basicity and pH of ash showed a broad range between 0.08-9.07 and 3.5-12.3, respectively. Some major inorganics in ash were identified and could affect the basicity. This could be one of the factors to determine further treatment means. Partitioning of hazardous heavy metals such as Pb, Cu, Cr, Hg and Cd was investigated. Large portions of Hg and Cd were emitted from the furnace while over 90% of Pb, Cu and Cr remained in bottom ash. However 54% of Hg was captured by WST and 41% by SDA/BF and 3.6% was emitted through the stack, while 81.5% of Cd was captured by SDA/BF. From the analysis data of various metal contents in ash and leach analysis, such capturing of metal was confirmed and some heavy metals found to be easily released from ash. Based on the overall characteristics of ash in different locations at the MSWI during the investigation, some considerations and suggestions for determining the appropriate treatment methods of ash were made as conclusions.     

Municipal solid waste management in Malaysia: Practices and challenges

Rapid economic development and population growth, inadequate infrastructure and expertise, and land scarcity make the management of municipal solid waste become one of Malaysia’s most critical environmental issues. The study is aimed at evaluating the generation, characteristics, and management of solid waste in Malaysia based on published information. In general, the per capita generation rate is about 0.5–0.8 kg/person/day in which domestic waste is the primary source. Currently, solid waste is managed by the Ministry of Housing and Local Government, with the participation of the private sector. A new institutional and legislation framework has been structured with the objectives to establish a holistic, integrated, and cost-effective solid waste management system, with an emphasis on environmental protection and public health. Therefore, the hierarchy of solid waste management has given the highest priority to source reduction through 3R, intermediate treatment and final disposal.     

Anaerobic digestion of food waste: comparing leachate exchange rates in sequential batch systems digesting food waste and biosolids

Over 35,000 tonnes of food waste are generated from high concentration point sources (i.e., restaurants, hospitals and markets) in metropolitan Adelaide (Australia) each year. Anaerobic digestion is a preferred method of treatment to degrade highly putrescible waste streams such as food waste due its high methane potential. To maximise methane yield, a sequential batch anaerobic system was chosen as the most appropriate system. Two sets of sequential batch systems consisting of mature and start-up reactors in triplicate exchanged leachate. One set exchanged twice as much leachate by volume as the other set to determine the effects of different leachate exchange volumes. Results show that by increasing the leachate volume between mature and start-up reactors, the time to degrade feedstock decreases, but total methane generation yields did not markedly differ, being 229LCH4 kg(-1) VSadded and 214LCH4 kg(-1) VSadded. Process parameters used to determine when to cease leachate exchange in start-up reactors were a pH of 6.5 and methane generation rate of >0.5LCH4 kg(-1) VSadded day(-1). Changes in carbon dioxide and methane biogas composition in the mature reactors reflected process stress caused by the addition of leachate with high VFA concentrations from the start-up reactors and indicate there may be limits to leachate exchange rates and subsequent loading of mature reactors.     

Site investigation on medical waste management practices in northern Jordan

This study investigated the medical waste management practices used by hospitals in northern Jordan. A comprehensive inspection survey was conducted for all 21 hospitals located in the study area. Field visits were conducted to provide information on the different medical waste management aspects. The results reported here focus on the level of medical waste segregation, treatment and disposal options practiced in the study area hospitals. The total number of beds in the hospitals was 2296, and the anticipated quantity of medical waste generated by these hospitals was about 1400 kg/day. The most frequently used treatment practice for solid medical waste was incineration. Of these hospitals, only 48% had incinerators, and none of these incinerators met the Ministry of Health (MoH) regulations. As for the liquid medical waste, the survey results indicated that 57% of surveyed hospitals were discharging it into the municipal sewer system, while the remaining hospitals were collecting their liquid waste in septic tanks. The results indicated that the medical waste generation rate ranges from approximately 0.5 to 2.2 kg/bed day, which is comprised of 90% of infectious waste and 10% sharps. The results also showed that segregation of various medical waste types in the hospitals has not been conducted properly. The study revealed the need for training and capacity building programs of all employees involved in the medical waste management.     

Anaerobic co-digestion of coffee waste and sewage sludge

The feasibility of the anaerobic co-digestion of coffee solid waste and sewage sludge was assessed. Five different solid wastes with different chemical properties were studied in mesophilic batch assays, providing basic data on the methane production, reduction of total and volatile solids and hydrolysis rate constant. Most of the wastes had a methane yield of 0.24-0.28 m3 CH4(STP)/kg VS(initial) and 76-89% of the theoretical methane yield was achieved. Reduction of 50-73% in total solids and 75-80% in volatile solids were obtained and the hydrolysis rate constants were in the range of 0.035-0.063 d(-1). One of the solid wastes, composed of 100% barley, achieved a methane yield of 0.02 m3 CH4(STP)/kg VS(initial), reductions of 31% in total solids, 40% in volatile solids and achieved only 11% of the theoretical methane yield. However, this waste presented the highest hydrolysis rate constant. Considering all the wastes, an inverse linear correlation was obtained between methane yield and the hydrolysis rate constant, suggesting that hydrolysis was not the limiting factor in the anaerobic biodegradability of this type of waste.