Summary:

The article presents the results of a research on the processing of undersize fraction, extracted from a stream of mixed municipal solid waste (MSW), into alternative fuel, in the process of bio-drying. The analysis was conducted with the use of an innovative EWA (Ecological Waste Apparatus) bioreactor adapted to carrying out aerobic treatment of waste in such processes as: composting, aerobic digestion/stabilization and bio-drying of waste. EWA bioreactors have been designed and manufactured by AGRO-EKO spol. s r.o. from the Czech Republic.
The subject matter of the analysis was undersize fraction, with particle dimensions ranging from 0 to 50 mm, manufactured in the process of sorting (mechanical processing) of MSW. The main aim of the research was to assess suitability of the use of EWA bioreactor in the process of alternative fuel production from undersize fraction developed from municipal waste (in the process of accelerated bio-drying). Samples were collected between 2011 and 2012. The undersize fraction and the produced alternative fuel were analysed by AGRO-EKO spol. s r.o. and at the University of Agriculture in Krakow, in accordance with the standards for wastes and solid fuels.
It has been concluded that undersize fraction produced from mixed municipal waste might be the energy source for cement plants or commercial power plants. As a result of a 66-hour accelerated process of bio-drying of undersize fraction (the standard time being ca. 7 days), the waste-mass has been lowered by reducing water content (moisture) in undersize fraction by ca. 15 % while increasing its calorific value and the C:N ratio. The process resulted in the increase of non-combustible and non-biodegradable elements. The high C:N ratio and the amount of organic substances at the level of 78 % should enable further aerobic and anaerobic stabilization preceded by substance moisturizing.