Source Separate Collection of Recyclables Reduces Chromium and Nickel Content in Municipal Solid Waste Compost

The composting process is a widespread option for municipal solid waste (MSW) treatment however the low rate of separate waste collection leads to poor quality composts. The evolution of heavy metal content in composts as a separate collection of dry recyclables became gradually implemented in the metropolitan area of Seville city (1 million inhabitants, SW Spain) is hereby studied. During the last 12 years, Cr, Ni, and Pb contents in compost were reduced by 60, 39, and 31%, respectively, whilst contents of Zn and Cd increased by 20 and 108%. During the same period Cu remained unchanged. The metal content reductions can be related to the separate collection of paper-cardboard, glass, and package waste from MSW, though materials separately collected were limited to 6.7% of raw MSW production. Extending the source collection of recyclables to separate metallic components and performing slight changes in the mechanical biological treatment would lead to additional reductions in other heavy metals whilst implementing the separate recovery of the organic fraction.