(best examples and good practices) on household organic waste ...

60
4. Materials Sorting Processes
4.1 Introduction
Materials Sorting Processes are used to provide a waste stream which could be
further used for the production of energy or composting, <strong>and</strong> a waste stream
which cannot be processed further, a fact which troubles modern societies <strong>and</strong>
brings them to the question of how to h<strong>and</strong>le the leftovers.
Solid waste is the unwanted or useless solid materials generated from
combined residential, industrial <strong>and</strong> commercial activities in a given area. It
may be categorized according to its origin (domestic, industrial, commercial,
construction or institutional); according to its contents (organic material, glass,
metal, plastic paper etc); or according to hazard potential (toxic, non-toxin,
flammable, radioactive, infectious etc). (Caribbean Youth Environment
Network.,2010)
The main waste fraction that needs to be separated from the mixed solid waste
stream is the organic (Biowaste, Kitchenwaste, Paper, etc). The modern
methods used for this separation are source separation <strong>and</strong> mechanical
biological treatment of mixed Municipal Solid Waste. The first method gives a
material clean from waste substances unwanted in the future treatment
processes (Composting, Anaerobic Digestion) for the production of compost
<strong>and</strong> biogas, which is better (in quality) than the MBT process.
4.2. Waste composition
There are different types of materials collected from households. The most
prominent materials are the following :( Wastesum.,2010)
Paper
Paper <strong>and</strong> paperboard are found in a wide variety of products in two categories
of MSW—nondurable <strong>good</strong>s <strong>and</strong> containers <strong>and</strong> packaging. In the nondurables
category, newspapers comprise a large portion of total MSW generation. Other
important contributions in this category come from office papers, <strong>and</strong>
commercial printing including advertising inserts in newspapers, reports,
brochures, <strong>and</strong> the like. Waste paper can be classified as bulk or high grade.
The highest grade includes manila folders, hard manila cards, <strong>and</strong> similar
computer-related paper products. High-grade waste paper is used as a pulp
substitute. Bulk grades consist of newspapers, corrugated cardboard, <strong>and</strong> mixed
paper waste (unsorted office or commercial paper waste). Bulk grades are used
to make paperboards, construction paper, <strong>and</strong> other products. The Institute of
Scrap Recycling Industries has established st<strong>and</strong>ards <strong>and</strong> <strong>practices</strong> that apply to
paper stock for repulping in the United States <strong>and</strong> Canada (ISRI., 2002). Over
the past decade, legislative programs have been developed in several countries
that require a certain percentage of recycled fiber content in newspaper, office