Implementation of a prototypal optical sorter as core of the new pre-treatment configuration of a mechanical-biological treatment plant treating OFMSW through anaerobic digestion

The pre-treatment of the organic fraction of municipal solid waste is one of the main challenges in mechanical–biological treatment plants equipped with anaerobic digesters. The present study shows the successful revamping of the Sant Adria del Besos plant pre-treatment line, where a prototypal optical sorter, a wet-crusher, and a hydrocyclone–decanter substituted the previous pulper and decanter system. The prototypal optical sorter, which uses near-infrared spectroscopy, was able to enhance the organic matter content from 40% to 60% in a more efficient and less energy demanding way than conventional systems. The new configuration not only improved digester feedstock and performance but also led to a significant reduction of the treatment and maintenance costs. The high methane yield of the digester, between 480 and 580CH4m3t−1VS, together with an energy efficiency index of 2.2kWhproduced/kWhconsumed, demonstrated the viability of this novel configuration with respect to conventional ones. Thus, optical sorting arises as a new alternative for mechanical–biological treatment plants that needs to be constructed or revamped.