The production of municipal solid waste has continued to grow in recent years. In Italy, municipal solid waste production reaches about 29 million tons per year. The organic fraction of municipal solid waste (OFMSW), which accounts for 30-40% of the total waste, usually undergoes biological treatments such as anaerobic digestion or composting, or is incinerated or landfilled. Biological treatments are considered not economically viable due to the long processing time (20-30 days), while incineration and landfilling are considered as low cost but polluting processes. In contrast, Hydrothermal Carbonization (HTC) is a cost-effective process to treat organic waste especially for the shorter processing time (0.5-8 h) and the possibility to treat directly wet heterogeneous materials. This thesis aims to investigate the potential use of HTC to upgrade OFMSW and other biomasses to biofuels or valuable byproducts. Chapter 1 gives an overview on the state of the art of HTC technology applied to organic wastes, focusing both on mechanisms and on the characteristics of reaction products. Chapter 2 investigates the potential use of HTC to upgrade the organic fraction of municipal solid waste (OFMSW) into biofuel and byproducts. The impact of process conditions (process time, temperature and solid load) on the formation, chemical and energy properties of hydrochar was deeply investigated. To analyze the behavior of hydrochar as a solid biofuel, the combustion (oxidation) of hydrochar and the co-firing (co-oxidation) of hydrochars and coals was also investigated. The results show that, especially at HTC harsher conditions, hydrochar is a “coal-like” material, that can be used as a valuable solid biofuel. The results evidenced that hydrochar is composed of primary char and secondary char. Primary char (non-extractable with organic solvents) has characteristics similar to coal and could be recovered for combustion, while secondary char is an amorphous and more volatile solid, easily extracted with organic solvents, which found possible application as a source of biochemicals and liquid bio-fuel. Chapter 3 investigates the use of HTC as a promising pre-treatment to enhance the biomethane potential during anaerobic digestion of OFMSW. Anaerobic digestion experiments were carried out using the HTC process liquid and the entire HTC reaction mixtures. Results proved that, when compared to the raw OFMSW, the use of HTC liquid and HTC mixture into AD lead to an increase of biomethane production of up to 37% and 363% by volume, respectively. Chapter 4 reports an HTC kinetics study and a kinetic model, which accounted for reactions leading to the production of primary and secondary char, as well as the liquid and gas phases. The model was optimized using experimental data performed on a lignocellulosic feedstock (olive trimmings) and validated on two other types of biomasses (grape marc and Opuntia Ficus Indica) and was used as a reliable tool to predict the carbon distribution among HTC products. In this chapter an in-depth analysis was also carried out to understand the evolution of feedstock characteristics during the heat-up transient phase before reaching the HTC set-point temperature. The results show that during heat up, the feedstock carbonized to a considerable extent at 220-250 °C. Tests clearly show evidence of the transition between thermal hydrolysis and HTC. Chapter 5 presents a study conducted to evaluate the economic feasibility and the detailed energy and cost analyses of a hypothetical HTC plant transforming wet biomass into pelletized dry hydrochar. To achieve these goals, a model was developed on the basis of experimental results obtained previously on two other organic materials (grape marc and off-specification compost). The results show that, when operating the HTC plant with grape marc at the optimal HTC conditions (T=220 °C, t=1 h, dry biomass to water ratio=0.19), the production cost of hydrochar were determined to be 157 €/ton, competitive with the price of wood pellets (150-200 €/ton). This makes HTC a promising process for a large development at the industrial scale.

Municipal solid waste (MSW) in Vietnam has been increasing quickly and became one of the most considered environmental problems in Mekong Delta (MD) region covering 13 provinces and municipalities in the south of Vietnam. With a considerably large amount of MSW, the region produces about 5% of the total amount of MSW of the country. The collection rate of solid waste is about quite high (65 - 72%) in the cities and rather low (about 40 - 55%) in the rural areas, with a high content in organic matter (about 60 - 85%). The climate of MD can be characterized as tropical and monsoonal with a high rate of humidity and a strong impact of flooding. Like other regions too, the MSW collection and treatment system is still underdeveloped and rudimentary, with disposal sites being the sole dumping method of the unsorted MSW remaining untreated by any mechanical and biological pre-treatment steps. Within this paper, the current treatment, management and operation of MSW systems are introduced, as well as the identification of advantages and disadvantages, environmental impacts, potential risks of the MSW system within the impact of global climate change. The situation of MSW treatment and management is correlated with the climate change impact and the integrated solid waste management is introduced as a new approach for adapting the environmental protection awareness by considering the climate change for the longterm sustainable development orientation. / Sự gia tăng chất thải rắn ở các đô thị Việt Nam ngày càng nhanh và chất thải rắn đang là một trong những vấn đề môi trường được quan tâm hàng đầu. Đồng bằng Sông Cửu Long (ĐBSCL) nơi có đến 13 tỉnh và thành phố nằm ở phía Nam Việt Nam. Với lượng chất thải không nhỏ, chiếm khoảng 5 % tổng lượng chất thải rắn sinh hoạt của quốc gia. Tỷ lệ thu gom chất thải rắn thấp, chiếm khoảng 65 - 72 % ở thành thị, tỷ lệ này ở nông thôn thấp 40 - 55%, chất thải có hàm lượng hữu cơ cao chiếm khoảng 60 - 85%. Khí hậu nhiệt đới gió mùa với độ ẩm không khí cao và chịu ảnh hưởng lớn của lũ lụt hàng năm. Cũng như các khu vực khác, hệ thống thu gom và xử lý rác thải ở khu vực ĐBSCL còn rất thô sơ và lạc hậu, bãi rác là nơi duy nhất tiếp nhận trực tiếp hổnhợp rác thải không phân loại và qua bất kỳ công đoạn tiền xử lý nào. Trong phạm vi bài viết này, chúng tôi giới thiệu hoạt động vận hành hệ thống quản lý và xử lý rác đô thị trong khu vực đồng thời phân tích các thuận lợi và bất lợi, cũng như các tác động môi trường, những rủi ro tiềm ẩn trong điều kiện ảnh hưởng của biến đổi khí hậu toàn cầu - khu vực ĐBSCL là nơi chịu ảnh hưởng nặng nề nhất. Tình hình quản lý và xử lý rác được cân nhắc trong điều kiện tác động của biến đổi khí hậu, đồng thời quản lý tổng hợp rác thải cũng được đề xuất như một các tiếp cận mới nhằm đáp ứng nhiệm vụ bảo vệ môi trường trong điều kiện biến đổi khí hậu theo định hướng phát triển bền vững lâu dài.

Today, solid waste management in coal mines is an urgent requirement for the coal mining industry. The overlying materials removed from a seam of coal are solid wastes transported to dumping sites and should be strictly, efficiently managed and monitored by an automatic system. These wastes must be separated for use as leveling and filling materials or residue materials need to be processed in order to minimize the impact on the environment. The system was designed to manage and monitor vehicles transporting solid waste in open coal mines to force them in tasks of taking solid wastes and giving out these wastes in the right places, to help collect and process suitably. The results showed that the calculation of numbers of trips using the software program named 'Management of trucks' achieved the statistics of running trucks between the points of removing wastes and dumping sites, in which the numbers of valid and invalid trips were given out. The monitoring process obtained the statistics of active and inactive total time of vehicles transporting solid waste. From that we can calculate and classify them at each dumping site. In addition, the statistics of productivity of power-shovels, fuel consumption levels of excavators and trucks were also gained. / Hiện nay quản lý chất thải rắn tại các mỏ than là một yêu cầu cấp bách đối với ngành khai thác than. Các chất thải khi bóc vỉa được chở đến các bãi đổ cần có một hệ thống quản lý giám sát chặt chẽ. Những chất thải này phải được phân loại để làm vật liệu san lấp hoặc vật liệu cần xử lý nhằm giảm thiểu các tác động tới môi trường. Hệ thống được thiết kế có nhiệm vụ quản lý và giám sát các xe chở chất thải trong quá trình khai thác tại các mỏ lộ thiên, đảm bảo các phương tiện này được xúc và đổ đúng nơi quy định, giúp thu gom, xử lý một cách phù hợp. Kết quả cho thấy rằng việc tính toán số lượng các chuyến xe bằng cách sử dụng chương trình phần mềm có tên là 'Quản lý xe tải' thu được các số liệu thống kê xe chạy giữa các điểm xúc chất thải và các điểm đổ, trong đó thống kê được số lượng các chuyến đi hợp lệ và không hợp lệ. Quá trình giám sát thu được các số liệu thống kê của tổng thời gian hoạt động và không hoạt động của các phương tiện vận chuyển chất thải rắn. Từ đó chúng tôi có thể tính toán và phân loại chúng ở mỗi điểm đổ chất thải. Ngoài ra, cũng thu được các số liệu thống kê năng suất hoạt động của máy xúc, mức tiêu thụ nhiên liệu của máy xúc và xe tải.

Incineration of municipal solid waste (MSW) is common for energy recovery, and management of municipal solid waste incineration (MSWI) ashes has received a growing attention around the world. In the U.S., generation of MSW has increased up to 65% since 1980, to the current level of 251 million tons per year with 53.8% landfilled, 34.5% recycled and composted, and 11.7% incinerated with energy recovery. In the process of incineration, MSWI ash is being produced as byproducts; about 80 to 90% of the MSWI ash is bottom ash (BA) and 10 to 20% is fly ash (FA) by weight. The current practice of the U.S. is to combine both BA and FA to meet the criteria to qualify as non-hazardous, and all combined ashes are disposed in landfills. European countries have utilized MSWI BA as beneficial construction materials by separating it from FA. The FA is mostly limited to landfill disposal as hazardous material due to its high content of toxic elements and salts. BA has been actively recycled in the areas of roadbed, asphalt paving, and concrete products in many of European and Asian countries. In those countries, recycling programs (including required physical properties and environmental criteria) of ash residue management have been developed so as to encourage and enforce the reuse of MSWI ashes instead of landfill disposal. Moreover, many studies have demonstrated the beneficial use of MSWI ashes as engineering materials with minimum environmental impacts. On the other hand, the U.S. has shown a lack of consistent and effective management plans, as well as environmental regulations for the use of MSWI ashes., Due to persistent uncertainty of engineering properties and inconsistency in the Federal and State regulations in the U.S., however, the recycling of the MSWI ashes has been hindered and they are mostly disposed in landfills. In this research work, current management practice, existing regulations, and environmental consequences of MSWI ashes utilization are comprehensively reviewed worldwide and nationwide with an emphasis of the potential area of its utilization in asphalt paving and concrete product. This research also entails a detailed chemical and microstructural characterization of MSWI BA and FA produced from a Refuse Derived Fuel (RDF) facility in Florida so that the MSWI ash is well characterized for its beneficial uses as construction materials. The material characterization includes Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction (XRD) techniques. In addition, leaching experiments have been conducted to investigate the environmental properties (e.g. leachate concentration) of BA and ash-mixed hot mix asphalt (HMA) and Portland cement concrete (PCC). Leaching results reveals the reduced leaching potential of toxic material from MSWI ashes while incorporated in HMA and PCC. Lastly, a preliminary experimental approach has been devised for the vitrification of FA which is a promising thermal process of transferring material into glassy state with higher physical and chemical integrity to reduce toxicity so that utilization of FA can be possible.

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Lack of genuine concern for solid waste management practices and inefficiency of sol-id waste management system is one of the greatest environmental issues in Addis Ab-aba, Ethiopia. The Current Municipal Solid Waste Management System is extremely inefficient and ineffective. An illegal waste dumping, inefficient waste collection, and informal recycling are some of the issues that need to be immediately rectified. There-fore, this study was conducted in order to get a knowledge transfer from a developed country, Sweden, Östersund Municipality. The practical waste management and recy-cling activities undertaking in the city of Östersund have been assessed, evaluated and discussed in the study. Physical site visits, surveys, informal interviews, and group dis-cussions have also been conducted to be able to draw an immensely useful and tangi-ble recommendation for the improvement of Solid Waste Management and Recycling Scheme in Addis Ababa. Based on the experience acquired from Östersund the entire Solid Waste Management system in Addis Ababa has been evaluated and useful dis-cussions, recommendations, and conclusions have been drawn. Besides as recycling is one of the most significant waste management hierarchy components, it should have been given top priority in reducing the amount of waste generation in developing countries like Ethiopia. However, the recycling activities taking place in the country are highly limited and informal. Moreover, evaluation of the potential of recyclable wastes in Addis Ababa, discussion on how and why recycling needs to be given prece-dence and later comparison is made with Östersund Municipality in order to be able to gain knowledge from the Swedish experience. Besides, discussions were made in order to address decisive measures that need to be taken to implement the Swedish experience in the Solid Waste Management and Recycling sector in Addis Ababa Ethiopia in an environmentally friendly and economical way.

Due to concern about diminishing landfill space, the City of Denton contracted a municipal solid waste characterization study in 1999 that would identify materials for diversion. This paper describes the results of 5 1-week waste sorting events, a scale-house analysis, a recycling participation study, a recycler profile and a similar city study. The results of the characterization studies suggest that at least 50% of each waste stream is recyclable or divertible though paper products accounted for no more than 45% by weight of any waste stream. Curbside recycling participation rate was 71% during the 6-week study period though the average weekly set-out rate was 37%. Recycling participation rates varied significantly by zip code and by home value categories but not by gender. Denton is fairly progressive in its waste management approach when compared to demographically similar cities on a 15-question assessment though recommendations for improvement have been identified.

published_or_final_version / abstract / toc / China Area Studies / Master / Master of Arts