Biological treatment of the organic fibre from the autoclaving of municipal solid wastes; preliminary results

Commingled municipal solid waste (MSW) was autoclaved in the presence of saturated steam for 30 min at 145 °C and 600 kPa. The organic fibre fraction from the autoclaved resulting material was examined for biodegradability. Aerobic and anaerobic tests were carried out to characterise the fibre in terms of biodegradation potential, which was moderate (biogas production potential of 251 ± 22 l [biogas] kg−1 [total solids (TS)] and dynamic respiration index (DRI) of 1575 ± 116 mg [O2] kg−1 [TS] h−1). Manual and chemical characterisations were also performed to organic fibre. Following this characterisation, a laboratory-scale thermophilic anaerobic digestion process and a pilot-scale composting process were carried out to determine the possibilities of these biological treatments. In the anaerobic digestion process the biogas yield values obtained were within 0.15–0.21 m3 [biogas] kg−1 [volatile solids (VS)] with an organic loading rate (OLR) of 3 kg [VS] m−3 d−1. However, it was difficult to reach the steady state in the anaerobic thermophilic process for the different organic loads tested. Further experiments are necessary to determine the optimal biogas production and performance under these conditions. The composting process performed correctly and the final material was stable (DRI of 504 ± 74 mg [O2] kg−1 [TS] h−1) and with good properties for its application to soil regarding heavy metal contents that corresponding to class B compost, with the exception of some metals that corresponded to class A.