From waste to fuel: Characterisation of the reject streams from a mechanical-biological treatment plant

Mechanical-biological treatment (MBT) plants are the most prevalent mixed municipal solid waste (MSW) treatment facilities in Europe. Their main function is to recover the maximum amount of recyclable materials and separate them from the biodegradable fraction, which undergoes an aerobic process for stabilization. The reject of an MBT plant consists of materials that could not be recovered and non-recyclable items. In Spain, these rejects are usually sent to landfills. To avoid this, energy recovery from rejects has emerged as an alternative, converting them into solid recovered fuel (SRF). The objective of this work was to study the physical and chemical composition of the different material streams from the biological treatment stage of an MBT plant located in the province of Castelló (Spain), in order to determine which of these streams can be transformed into SRF. For this purpose, two sampling campaigns were carried out. Among the properties analyzed, the combustible fraction and its biowaste content are worth highlighting, as biowaste is considered a renewable resource. In all six analyzed streams, the combustible fraction exceeded 76%, while the biomass combustible fraction was greater than 55%. The high biowaste content of the reject adds significant value when it is transformed into SRF.