2007:04 Hantering av förpackat livsmedelsavfall - Avfall Sverige

DEWASTER ® - Sorting out the problems of mixed waste
household preferences and practises unsorted MSW display a significant differences in composition
from country to country or even between regions and cities within individual countries.
Below is given an indication of the nature of the six fractions of waste separated during EPA study in
Odense.
Bulk refuse
Bulk refuse consist in a variety of singular large items such as bicycle frames, plastic buckets, discarded
electronic appliances etc. which are not allowed in the MSW, but placed in the MSW by mistake
or through neglect.
Screen fraction (pre-sorting reject)
The screen fraction is very light and contains mainly plastic, paper, cardboard and textiles. The components
are relatively large and intact and therefore easily recognisable. Some of the common components
are plastic bags, newspapers, food packaging and diapers.
Metal
The metal fraction consisted in cans, bottle caps, cutlery and similar, and accounted for app. 2 percent
of the total in put of MSW. The sorting quality and the type of magnet used was not optimised during
the study and, thus, higher yields of metals for recycling may well be possible.
Oversize
A special device (DESIZER) takes out smaller hard items like non-ferro metal objects, bones,
stones, ceramics and pieces of wood prior to the DEWASTER® press in order to increase press efficiency,
prevent blockage and to prolong press life.
Press reject
The press reject is the dry fraction from the DEWASTER® screw-press. The fraction contains mainly
paper- and plant fibres, plastic and non-organic components such as gravel, glass and aluminium.
There are basically three ways of disposing this fraction: Incineration in a waste incinerator, co-burning
in industrial plants or composting prior to landfill. In respect to incineration and co-burning the Danish
EPA study concludes that press reject due to higher ash contents (i.e. contents of incombustible nonorganic
material) has a lower heat value and a higher level of alkali metals and glass particles than
average MSW, but a lower level of chloride
Bio pulp
Bio pulp is a brown/grey pasty mush, which resemble sewage sludge, but generally without any smell
of rotten material. The bio pulp is easily digestible in anaerobic processes and after addition to a bio
gas reactor, an increase in gas production is typically seen within one hour.
The average yield of bio pulp achieved during the EPA study was 23 % of the in put MSW with 29-
34 % dry matter. In Odense the OFMSW accounts for app. 39 % of the total unsorted MSW. The yield
of 23 % in this study means that app. 59 % of the organic material was sorted out of the MSW. This is
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