Abstract:The paper presents the current situation of the waste management system of the megacity Ho Chi Minh in Vietnam, and the options for waste and land recycling in a low income country. Generally, there is a large potential for circular economy in the city as the main proportion of the waste flows are recyclables. Due to the missing selective collection system, this potential is not used in the full extend yet, even if the collection of the entire waste volumes is envisaged in the National Waste Management Strategy by 2025. The waste stocks are the landfill locations in the region of Ho Chi Minh City (HCMC), two of them being in operation and two of them already being closed. A special focus is given to the landfill GÈ Cát, which was subject to an option analysis in terms of waste and land recycling options. The results indicate that there are several reuse options: the use of the landfill material in a waste-to-energy process after landfill mining, the reuse of the re-gained land in case of landfill mining, the reuse of the capped landfill for energy crop cultivation, and the gasification in a biogas plant in case of a remaining landfill.

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Economic activities performed by rural populations linked to informal trading and markets have not received a broad attention in the literature. Thus, the question of the present investigation is the role of the informal sector in a rurbanised environment, and if there are differences in the waste management activities of the informal sector in cities and in an urbanised rural environment. To obtain information about the informal waste pickers in the rural areas, data were collected directly through a questionnaire from the following countries (sorting in alphabetic order): Austria,

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Urbanization processes in Asia are still ongoing; thus, aggregate demand is expected to increase in following years. Even though construction and demolition waste is a source for secondary building materials in industrialized countries, it is not yet an alternative construction material source in Vietnam as the urbanization process is still ongoing. Thus, there is a need for river sand and aggregates alternatives in concrete, namely manufactured sand (m-sand) from primary solid rock materials and secondary waste materials. The focus in the present study for Vietnam was on m-sand sand as alternative for river sand, and different ashes as alternatives for cement in concrete. The investigations comprised concrete lab tests according to the formulations of concrete strength class C 25/30 in accordance with DIN EN 206, followed by a lifecycle assessment study in order to identify the environmental impact of the alternatives. In total 84 samples were investigated, consisting of 3 reference samples, 18 samples with primary substitutes, 18 samples with secondary substitutes, and 45 samples with cement substitutes. This kind of holistic investigation approach comprising material alternatives and accompanying LCA was the first study for Vietnam, and even for Asia, and represents a substantial added value for future policy development in order to cope with resource scarcity. The results show that with the exception of metamorphic rocks, all m-sands meet the requirements for quality concrete. In terms of cement replacement, the mixes showed that a higher percentage of ash reduces the compressive strength. The compressive strength values of the mixes with up to 10% coal filter ash or rice husk ash were equivalent to the C25/30 standard concrete formulation. Higher ash contents up to 30% lead to the reduction of the concrete quality. The LCA study’s results highlighted the better environmental footprints across environmental impact categories in the 10% substitution material in comparison to the use of primary materials. The LCA analysis results showed that cement as a component in concrete holds the highest footprint. The use of secondary waste as alternative for cement provides significant environmental advantage.