What is waste, and how we manage it

Mariachiara Zanetti, Deborah Panepinto (Department of Environment, Land and Infrastructure Engineering - Politecnico di Torino)

Currently, a management of solid residues compatible with current legislation prescriptions involves the minimization of the produced waste at the source, the recovery of the useful fractions still present in the waste for the replacement of a part of the raw materials (reuse, recycling) and/or energy production and, at last, the environmentally compatible disposal of the remaining waste amount.

Reduction at source and recycling are the two ways in which waste minimization can be achieved. The reduction at the source can be obtained through a series of interventions including: the replacement of the product or the variation of the chemical and physical composition, the replacement of raw materials with others involving less waste, changes in process and operating parameters, adoption of good operational practices aimed at minimizing waste. Reuse and recycling of waste can include one or more of the following options: use in one or more processes, treatment for re-use, exchange or sale.

The energy recovery in proper plants is an option for waste fractions characterized by high calorific power.

In order to evaluate the best recovery solution for a specific waste the physical and chemical characterization of residues is required.

The various types of treatment are based on physical and chemical processes.

Physical processes use differences in one or more physical properties between the constituents in order to separate objects, grains, particles of different composition from each other. It is essential that the differences in a given physical property correspond to the difference in composition that is of interest for the final purpose of the process. The main physical separation operations are screening (vibrating, rotating screens, etc.), classification in fluid medium (settler, counter-current separator, cyclone), differential comminution (particle size reduction by comminution and subsequent screening), magnetic separation and electrical separation.

Chemical processes are procedures in which the goal of separating constituents is achieved by separating molecules, atoms, ions or by state transformations. The main chemical operations are the dissolution followed by selective precipitation and the combustion, gasification and pyrolysis processes.

The final disposal of waste and scraps from the various treatment operations takes place in landfills in accordance with current regulations.

Some examples of reuse/recycling of wastes will be presented together with the environmental assessment of performed operations.

Panepinto, Deborah; Zanetti, Mariachiara, Municipal solid waste incineration plant: A multi-step approach to the evaluation of an energy-recovery configuration, WASTE MANAGEMENT, Elservier, pp. 10, 2018, Vol. 73, ISSN: 0956-053X, DOI: 10.1016/j.wasman.2017.07.036.

Ruffino, Barbara; Fiore, Silvia; Zanetti, Mariachiara, Strategies for the enhancement of automobile shredder residues (ASRs) recycling: results and cost assessment, WASTE MANAGEMENT, Elsevier, pp. 8, 2014, Vol. 34, ISSN: 0956-053X, DOI: 10.1016/j.wasman.2013.09.025