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Basic geotechnical parameters of biodried waste from winter and summer period

One of the possible ways of disposing of municipal solid waste (MSW) is mechanicalbiological treatment (MBT), originally developed in Germany with the aim of reducing the amount of biodegradable waste before landfilling. The process consists of a mechanical treatment step in which the waste is mechanically separated to collect recyclable materials, and a biological treatment step in which the waste can be treated by biodrying, composting or digestion of the organic fraction and has several types of outputs (waste fuel, stabilised organic waste, ferrous and non - ferrous metals, and inert waste). Apart from useful products, one part of the waste from the MBT process cannot be used as waste fuel or recyclable material but is still quite rich in organic matter. This type of waste, called the methanogenic fraction, goes to a bioreactor landfill where water is added and recirculated, in order to accelerate or increase the biodegradation of biodried waste, after which biogas is extracted. Bioreactor landfills are equipped with liners and leachate collection systems. Contrary to the usual so-called “dry” landfills, bioreactor landfills will experience faster settlements due to an increased solid waste decomposition rate, and increased pressure due to increased unit weight. Adding water to the waste to increase the biological activity increases the total mass of the waste which can cause an increase in pore pressure. For these reasons, it is necessary to determine the basic geotechnical parameters of waste disposed into bioreactor landfills. This paper presents the established basic geotechnical parameters (moisture content, organic matter content and particle size analysis of waste) and other properties (waste composition, waste classification by form into 1D, 2D and 3D shapes), on samples of the methanogenic fraction with maximum particle size of about 25 mm. Waste samples were taken during the winter (February 2019) and summer (July 2020) periods from the Croatian Waste Management Centre, Marišćina. In order to establish the influence of seasonal variation of waste material the obtained basic geotechnical parameters were compared. The comparison shows small differences which could be attributed to the heterogeneity of the studied waste material. Nevertheless, samples from both time periods are very similar, and therefore they should not cause major differences in plant operation during the year.

Biodried waste, Bioreactor landfill, methanogenic fraction, basic geotechnical parameters

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