Hydrothermal carbonization of food waste and associated packaging materials for energy source generation

Hydrothermal carbonization (HTC) is a thermal conversion technique that converts food wastes and associated packaging materials to a valuable, energy-rich resource. Food waste collected from local restaurants was carbonized over time at different temperatures (225, 250 and 275 °C) and solids concentrations to determine how process conditions influence carbonization product properties and composition. Experiments were also conducted to determine the influence of packaging material on food waste carbonization. Results indicate the majority of initial carbon remains integrated within the solid-phase at the solids concentrations and reaction temperatures evaluated. Initial solids concentration influences carbon distribution because of increased compound solubilization, while changes in reaction temperature imparted little change on carbon distribution. The presence of packaging materials significantly influences the energy content of the recovered solids. As the proportion of packaging materials increase, the energy content of recovered solids decreases because of the low energetic retention associated with the packaging materials. HTC results in net positive energy balances at all conditions, except at a 5% (dry wt.) solids concentration. Carbonization of food waste and associated packaging materials also results in net positive balances, but energy needs for solids post-processing are significant. Advantages associated with carbonization are not fully realized when only evaluating process energetics. A more detailed life cycle assessment is needed for a more complete comparison of processes.     

Estimation of residual MSW heating value as a function of waste component recycling

Recycling of packaging wastes may be compatible with incineration within integrated waste management systems. To study this, a mathematical model is presented to calculate the fraction composition of residual municipal solid waste (MSW) only as a function of the MSW fraction composition at source and recycling fractions of the different waste materials. The application of the model to the Lisbon region yielded results showing that the residual waste fraction composition depends both on the packaging wastes fraction at source and on the ratio between that fraction and the fraction of the same material, packaging and non-packaging, at source. This behaviour determines the variation of the residual waste LHV. For 100% of paper packaging recycling, LHV reduces 4.2% whereas this reduction is of 14.4% for 100% of packaging plastics recycling. For 100% of food waste recovery, LHV increases 36.8% due to the moisture fraction reduction of the residual waste. Additionally the results evidence that the negative impact of recycling paper and plastic packaging on the LHV may be compensated by recycling food waste and glass and metal packaging. This makes packaging materials recycling and food waste recovery compatible strategies with incineration within integrated waste management systems.     

Potentials for the prevention of municipal solid waste

Waste prevention has been assigned the highest priority under European waste management law. However, the initiatives which have been taken so far have not reduced the regular annual increase in total waste arising across Europe. The purpose of this paper is to quantify and analyze in depth the prevention potential for selected case studies (advertising material, beverage packaging, diapers, food waste, waste from events). Only such measures are considered, which do not require a reduction of consumption. The prevention potentials for household waste in theory are exemplified for the city of Vienna, also with a view to barriers that may reduce the achievable prevention potential. The results show that the prevention potentials for the analyzed individual measures can reach an order of magnitude of some 10% of the relevant waste stream (e.g., advertising material, beverage packaging), or rather 1-3% of municipal solid waste. The prevention potentials appear to be relatively small in relation to the total municipal waste quantities. Methodological shortcomings, such as the missing availability of basic data, make it difficult to exactly estimate the impact of waste prevention measures on waste quantities, which is only one of the effects of waste prevention among other ecological, social and economic aspects.     

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.     

Inconsistent pathways of household waste

The aim of this study was to provide policy-makers and waste management planners with information about how recycling programs affect the quantities of specific materials recycled and disposed of. Two questions were addressed: which factors influence household waste generation and pathways? and how reliable are official waste data? Household waste flows were studied in 35 Swedish municipalities, and a wide variation in the amount of waste per capita was observed. When evaluating the effect of different waste collection policies, it was found to be important to identify site-specific factors influencing waste generation. Eleven municipal variables were investigated in an attempt to explain the variation. The amount of household waste per resident was higher in populous municipalities and when net commuting was positive. Property-close collection of dry recyclables led to increased delivery of sorted metal, plastic and paper packaging. No difference was seen in the amount of separated recyclables per capita when weight-based billing for the collection of residual waste was applied, but the amount of residual waste was lower. Sixteen sources of error in official waste statistics were identified and the results of the study emphasize the importance of reliable waste generation and composition data to underpin waste management policies.     

Selective collection as a pretreatment for indirect solid recovered fuel generation

Effective selective collection (SC) has been increasing in many countries of the European Union. As a consequence the composition of residual municipal solid waste (RMSW) is changing not only because of economic development, but also due to the collection system. The input of RMSW treatment plants is thus not homogeneous. This paper analyses two case studies involving a total of five SC scenarios and their impact on the generation of solid recovered fuel (SRF) with/without bio-drying, post-treatment and packaging take back programs (TBPs). These case studies are based on two types of SC: kerbside and drop-off. The latest regulation on SRF classification is taken into account: energy content, Cl and Hg concentrations are assessed and discussed. The role of the respirometric index (RI) is also analyzed. Results show that when SC is highly efficient RMSW can be classified directly as SRF, but only if the introduction of RI does not set stringent respirometric targets. The role of packaging TBPs is important as the residual waste remaining after the packaging has been processed, can be valorized increasing the lower heating value (LHV) of the residual RMSW and minimizing the streams that should be landfilled. The source separation of food waste has a significant impact on the suitability of bio-drying: when the SC of food waste is very efficient, its percentage in the RMSW may be too low for effective bio-drying.     

Production patterns of packaging waste categories generated at typical Mediterranean residential building worksites

The construction sector is responsible for around 28% of the total waste volume generated in Europe, which exceeds the amount of household waste. This has led to an increase of different research studies focusing on construction waste quantification. However, within the research studies made, packaging waste has been analyzed to a limited extent. This article focuses on the packaging waste stream generated in the construction sector. To this purpose current on-site waste packaging management has been assessed by monitoring ten Mediterranean residential building works. The findings of the experimental data collection revealed that the incentive measures implemented by the construction company to improve on-site waste sorting failed to achieve the intended purpose, showing low segregation ratios. Subsequently, through an analytical study the generation patterns for packaging waste are established, leading to the identification of the prevailing kinds of packaging and the products responsible for their generation. Results indicate that plastic waste generation maintains a constant trend throughout the whole construction process, while cardboard becomes predominant towards the end of the construction works with switches and sockets from the electricity stage. Understanding the production patterns of packaging waste will be beneficial for adapting waste management strategies to the identified patterns for the specific nature of packaging waste within the context of construction worksites.     

The future course of solid waste management in the U.S.

It is postulated that the current “garbage crisis” is due to a shortage of disposal capacity, not to burgeoning amounts of municipal solid waste (MSW). In support of this, trends in the quantity and composition of MSW, methods of waste reduction, recycling and growth of waste-to-energy capacity are examined to gain insight as to the future course of MSW management in the U.S. over about the next 15 plus years. This is the likely time to install new disposal capacity if pending legislative proposals are passed, that would enable states that provide their own disposal to ban wastes from other states.A new term, the “intensity of waste generation”, is proposed and illustrated, analogous to the intensity of mineral usage. The intensity is decreasing, implying that it is unlikely that waste generation will grow at rates projected by extrapolation or simple macroeconomic assumptions. Some other conclusions are: per capita MSW generation was nearly statistically constant from 1970 to 1984; the content of most forms of packaging in MSW are decreasing; packaging decreases the amount of food residues in MSW; and proposed national recycling targets of about 25% or more are not likely to be achieved, in part because of changes in the composition of MSW. Coupled with likely shortages of labor to process separated waste, it is forecast that there will be some future time when people will not think source separation is worth the bother and recycling will decrease. The future growth of waste-to-energy capacity is projected by assuming that a city will install capacity when others have done so, which leads to a simple quantitative model. The likely effects of impending landfill and incineration regulations are addressed.     

Characterizing emissions from open burning of military food waste and ration packaging compositions

Emissions from open burning of military food waste and ration packaging compositions were characterized in response to health concerns from open burning disposal of waste, such as at military forward operating bases. Emissions from current and prototype Meals, Ready-to-Eat (MREs), and material options for their associated fiberboard packaging were quantified to assess contributions of the individual components. MREs account for 67–100% of the particulate matter (PM), volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated dibenzo-p-dioxins and -furans (PCDDs/PCDFs) emissions when burned in unison with the current fiberboard container and liner. The majority of the particles emitted from these burns are of median diameter 2.5 µm (PM_2.5). Metal emission factors were similar regardless of waste composition. Measurements of VOCs and PAHs indicate that targeted replacement of MRE components may be more effective in reducing emissions than variation of fiberboard-packaging types. Despite MRE composition variation, equivalent emission factors for PM, PAH, VOC, and PCDD/PCDF were seen. Similarly, for fiberboard packaging, composition variations exhibited essentially equivalent PM, PAH, VOC, and PCDD/PCDF emission factors amongst themselves. This study demonstrated a composition-specific analysis of waste burn emissions, assessing the impact of waste component substitution using military rations.     

A review of municipal solid waste composition in the United Kingdom

The move from landfill-based to resource-based waste management systems requires a greater knowledge of the composition of municipal solid waste. This paper draws together the findings of municipal solid waste (MSW) compositional surveys undertaken in the United Kingdom. The results from recent surveys show a good agreement over the composition of household-collected waste, but less agreement over civic amenity site waste composition. There is insufficient data to allow comparisons of the commercial waste element of municipal waste or of the other components, and further work is necessary to produce more reliable estimates of the composition of these streams. The use of questionnaire surveys and analysis of the results suggests that the size and age profile of a household influence the generation of household-collected waste. Some research suggests that the waste container provided by the local authority and the socio-economic classification of a household also influence household-collected waste generation, but other studies failed to find this link. Further research is required to investigate this by surveying all of the waste disposal routes available to specific households.     

Municipal solid waste composition and food loss reduction in Kyoto City

For 35 years, Kyoto City has conducted detailed household waste composition surveys under the guidance of Kyoto University by dividing household waste into approximately 400 categories. In addition, the city has conducted detailed composition surveys of commercial waste generated by businesses. These surveys show that food loss accounts for approximately 40% of total waste, of which leftovers and untouched food account for about 40% in both households and business facilities. Consequently, the annual generation of household and commercial food loss is estimated at about 30,000 tons. Various efforts have been made to reduce waste, including food loss, but further reduction in environmental burden is needed. Thus, Kyoto City revised the ordinance for waste reduction, and in March 2015, formulated a new municipal waste management plan. The plan not only includes the 2Rs (reduce, reuse), but also, for the first time in Japan, sets quantitative targets for reducing food loss. Kyoto City must ensure that the necessary waste reduction measures are clearly explained to the residents and business operators. To ensure that this plan is successful, it is important to clarify concrete actions that residents and business operators should implement, along with their effects.     

Effect of mixing ratio of woody waste and food waste on the characteristics of carbonization residue

Biomass such as woody waste and food waste can be converted to a renewable energy source by means of carbonization processes. The basic characteristics of woody waste and food waste, such as proximate analysis and heating value, were evaluated before carrying out carbonization tests. Carbonization tests were carried out to obtain the basic characteristics of carbonization residue on changing the proportion of food waste from 0% to 30% in the mixture of woody waste and food waste. The effect of the food waste was estimated by basic characteristics of the residue such as the heating value, yield, and fuel ratio. As increased the food waste content, the bulk density, yield and chlorine content of the carbonization residue increased, but fuel ratio, the carbon content and heating value of the residue decreased. From the results of the basic characteristics of the residue, the optimum food waste content in carbonization tests was found to be 20%. Even if food waste is combined with woody waste at levels up to 30%, the sulfur and chlorine concentrations in the residue were much lower than the regulatory standard levels. From the results for the fuel ratio and heating value of the residue, the carbonization residue is suitable for use as a renewable energy source and can be categorized by the second grade level of solid fuel products.     

Factors that affect the quality of the bio-waste fraction of selectively collected solid waste in Catalonia

The present study determines the composition of the bio-waste fraction of waste and establishes correlations between the quality of this fraction and socio-economic/demographic variables. According to the Catalan Waste Agency [Agència de Residus de Catalunya (2004). Statistical data. Available from: ], the quantities of glass, paper/cardboard, light packaging and biodegradable material (those components of municipal waste that can be recovered, and have a separate collection) that were selectively collected in 2004 represent 25.6% by weight of the total municipal waste generated. There is a large spread of values from different cities. It is important to bear in mind that this percentage was calculated using the total weights of all of the materials present in the different bins used for selective solid waste collection, without taking account of the fact that many of these bins contain a certain amount of other, undesirable waste. In order to be able to determine the actual quantities that are recovered, it is necessary to establish the quality of the waste collected. To establish the quality of the waste collected, 350 samples were analysed, corresponding to the bins for the bio-waste fraction of solid waste in 193 different cities in Catalonia. Seven levels of quality were established for the study, depending on the amount of undesirable waste present. The results show certain correlations between the socio-economic/demographic factors studied and the percentage of undesirable waste present in the samples. The correlations presented here are not intended to be predictive, but rather indicative of a tendency, which should help us gain a better understanding of the behaviour of the society studied with respect to the separation of solid household waste at origin.     

Fundamental characteristics of input waste of small MSW incinerators in Korea

Waste incineration in a small incinerator is a simple and convenient way of treating waste discharged from small areas or from large facilities and buildings such as business centers, marketplaces, factories, and military units. Despite their ostensible advantages, however, many small incinerators frequently suffer from serious problems, e.g., unsystematic waste feeding, unstable combustion, deficient air pollution control devices, and consequently, environmental pollution. To obtain a better understanding of the characterization of wastes in small incinerators, we investigated a series of fundamental characteristics, i.e., physical composition, bulk density, proximate and ultimate analysis, potential energy content, and so on. The main waste components in small incinerators were identified as paper and plastic; the proportion of food waste was less than that in large incinerators. Especially, a low ratio of food waste had a strong influence on other waste characteristics, e.g., lower moisture content and bulk density, and higher potential energy. On the other hand, in contrast with that of HCl, there was no distinguishable linear relationship between Cl content in waste and PCDD/DF concentration in combustion gas.     

Packaging waste recycling in Europe: Is the industry paying for it?

This paper describes and examines the schemes established in five EU countries for the recycling of packaging waste. The changes in packaging waste management were mainly implemented since the Directive 94/62/EC on packaging and packaging waste entered into force. The analysis of the five systems allowed the authors to identify very different approaches to cope with the same problem: meet the recovery and recycling targets imposed by EU law. Packaging waste is a responsibility of the industry. However, local governments are generally in charge of waste management, particularly in countries with Green Dot schemes or similar extended producer responsibility systems. This leads to the need of establishing a system of financial transfers between the industry and the local governments (particularly regarding the extra costs involved with selective collection and sorting). Using the same methodological approach, the authors also compare the costs and benefits of recycling from the perspective of local public authorities for France, Portugal and Romania. Since the purpose of the current paper is to take note of who is paying for the incremental costs of recycling and whether the industry (i.e. the consumer) is paying for the net financial costs of packaging waste management, environmental impacts are not included in the analysis. The work carried out in this paper highlights some aspects that are prone to be improved and raises several questions that will require further research. In the three countries analyzed more closely in this paper the industry is not paying the net financial cost of packaging waste management. In fact, if the savings attained by diverting packaging waste from other treatment (e.g. landfilling) and the public subsidies to the investment on the “recycling system” are not considered, it seems that the industry should increase the financial support to local authorities (by 125% in France, 50% in Portugal and 170% in Romania). However, in France and Portugal the industry is paying local authorities more than just the incremental costs of recycling (full costs of selective collection and sorting minus the avoided costs). To provide a more definitive judgment on the fairness of the systems it will be necessary to assess the cost efficiency of waste management operators (and judge whether operators are claiming costs or eliciting “prices”).     

Influence of assumptions about household waste composition in waste management LCAs

This article takes a detailed look at an uncertainty factor in waste management LCA that has not been widely discussed previously, namely the uncertainty in waste composition. Waste composition is influenced by many factors; it can vary from year to year, seasonally, and with location, for example. The data publicly available at a municipal level can be highly aggregated and sometimes incomplete, and performing composition analysis is technically challenging. Uncertainty is therefore always present in waste composition. This article performs uncertainty analysis on a systematically modified waste composition using a constructed waste management system. In addition the environmental impacts of several waste management strategies are compared when applied to five different cities. We thus discuss the effect of uncertainty in both accounting LCA and comparative LCA. We found the waste composition to be important for the total environmental impact of the system, especially for the global warming, nutrient enrichment and human toxicity via water impact categories.     

Overview of waste disposal and landfills/dumps in Asian countries

Many cities in developing Asian countries face serious problems in managing solid wastes. The annual waste generation increases in proportion to the rises in population and urbanization. Asian countries with greater rural populations produce more organic waste, such as kitchen wastes, and fewer recyclable items, such as paper, metals, and plastics. Reliable data on solid waste compositions are difficult to obtain, and even if available, they are often not updated. We report the most recent waste composition data in some developing Asian countries. We suggest that a better classification system for landfills is needed to address inconsistencies in data for sanitary landfill sites versus waste dumps. We also discuss the information on waste disposal trends and problems associated with general solid waste management in developing Asian countries.     

A model for quantifying construction waste in projects according to the European waste list

The new EU challenge is to recover 70% by weight of C&D waste in 2020. Literature reveals that one major barrier is the lack of data. Therefore, this paper presents a model which allows technicians to estimate C&D waste during the design stage in order to promote prevention and recovery. The types and quantities of CW are estimated and managed according to EU guidelines, by building elements and specifically for each project. The model would allow detection of the source of the waste and to adopt other alternative procedures which delete hazardous waste and reduce CW. Likewise, it develops a systematic structure of the construction process, a waste classification system and some analytical expressions which are based on factors. These factors depend on technology and represent a standard on site. It would allow to develop a database of waste anywhere. A Spanish case study is covered. Factors were obtained by studying over 20 dwellings. The source and types of packaging waste, remains, soil and hazardous waste were estimated in detail and were compared with other studies. Results reveal that the model can be implemented in projects and the chances of reducing and recovery C&D waste could be increased, well above the EU challenge.     

Controlled combustion tests and bottom ash analysis using household waste with varying composition

The influence of the co-combustion of household waste with either sewage sludge, shredder fluff, electronic and electrical waste (WEEE) or PVC on the bottom ash quality and content was investigated under controlled laboratory conditions using a pot furnace. This laboratory approach avoids the interpretation problems related to large variations in input waste composition and combustion conditions that are observed in large scale MSW incinerators. The data for metals content, transfer coefficients and leaching values are presented relative to data for a base household waste composition that did not contain any of the added special wastes. The small WEEE invited direct measurement of precious metals content in the ashes, where measurement accuracy is facilitated by using only mobile phone scrap for small WEEE. The analyses were carried out for different particle size ranges that are of relevance to the recyclability of metals and minerals in the ashes. Positive correlations were found between elements content of the input waste and the bottom ashes, and also between increased levels of Cl, Mo and Cu in the input waste and their leaching in the bottom ashes. These correlations indicate that addition of PVC, small WEEE and shredder fluff in input waste can have a negative influence on the quality of the bottom ashes. Enrichment of Au and Ag occurred in the fractions between 0.15 and 6 mm. The precious metals content represents an economically interesting intrinsic value, even when the observed peak values are properly averaged over a larger volume of ashes. Overall, it has been shown that changes in quality and content of bottom ashes may be traced back to the varied input waste composition.     

Does industrial waste taxation contribute to reduction of landfilled waste? Dynamic panel analysis considering industrial waste category in Japan

Waste taxes, such as landfill and incineration taxes, have emerged as a popular option in developed countries to promote the 3Rs (reduce, reuse, and recycle). However, few studies have examined the effectiveness of waste taxes. In addition, quite a few studies have considered both dynamic relationships among dependent variables and unobserved individual heterogeneity among the jurisdictions. If dependent variables are persistent, omitted variables cause a bias, or common characteristics exist across the jurisdictions that have introduced waste taxes, the standard fixed effects model may lead to biased estimation results and misunderstood causal relationships. In addition, most existing studies have examined waste in terms of total amounts rather than by categories. Even if significant reductions in total waste amounts are not observed, some reduction within each category may, nevertheless, become evident.Therefore, this study analyzes the effects of industrial waste taxation on quantities of waste in landfill in Japan by applying the bias-corrected least-squares dummy variable (LSDVC) estimators; the general method of moments (difference GMM); and the system GMM. In addition, the study investigates effect differences attributable to industrial waste categories and taxation types. This paper shows that industrial waste taxes in Japan have minimal, significant effects on the reduction of final disposal amounts thus far, considering dynamic relationships and waste categories.