Separation of biodegradable material from the low calorific fraction of municipal solid waste

The increasing concerns regarding climate change and depletion of raw materials motivate governments to intensify their actions towards a cleaner energy matrix, independent of fossil fuels, and a more sustainable material supply chain. In this context, municipal solid waste (MSW) is of major interest, considering it contains a variety of potentially valuable materials, such as biomass (e.g. food and green waste) and recyclables (e.g. plastics, glass, mineral fractions, etc.). However, when suitable local infrastructure for the separation of these materials does not exist, MSW is usually discarded in landfills or thermally treated. Often, the thermal treatment involves transportation over long distances. The objective of this work was to develop a pilot mechanical pretreatment system for the separation of MSW (fraction <12 mm) into a substrate rich in biodegradable material for local valorization. The developed pretreatment consists of a sieving step followed by a mixing unit, which produces a suspension to be fed into a hydrocyclone. The impurity separation efficiency of the hydrocyclone was evaluated for different total solids (TS) of the suspension and for different volume flows (VF). For practical applications, the TS of 9% and VF of 10 m(3)/h presented the optimal arrangement for impurity removal. In addition, after passing the MSW-derived suspension through the hydrocyclone three times, it was possible to increase the concentration of biodegradable material from 40% TS to 65% TS. The removed impurities consisted of 90% minerals, glass and metals, presenting potential of further processing for the extraction of secondary raw materials prior to landfilling. The specific electricity demand of the proposed wet pretreatment was estimated at 3.2 kWh/t of MSW <12 mm processed. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The study aimed to develop a mechanical pretreatment system to separate municipal solid waste (MSW) into a substrate rich in biodegradable material for local valorization. The research results showed that through specific processing steps, the concentration of biodegradable materials can be significantly increased.