2. Methodology
This study investigated how changes in assumptions regarding
waste composition affect the modelled environmental impact of a
waste management system. This was achieved by first identifying a
representative waste management system for Norwegian conditions.
Then an average waste composition was estimated, using a
fairly low level of aggregation. Next we decided how the waste
composition should be systematically modified in the assessment
and which sorting efficiencies should be used. In conclusion we
looked at how environmental impact was affected by changes in
sorting efficiencies and technology in an assessment of five cities
with different waste compositions.
2.1. Waste management system
A hypothetical Norwegian household waste management system
was modelled. In 2011 56% of Norwegian household waste
was incinerated, 40% was collected for recycling, 2% was landfilled
and 2% received other treatment (SSB, 2012a). Landfilling of organic
waste was forbidden in 2009. Most municipalities collect from
households using a two- or three-bin, or container, system. In addition
most municipalities have neighbourhood collection points,
where household deliver glass and metal waste for recycling.
Household source-separated waste such as wood, garden waste,
EE-waste and hazardous waste has to be brought to recycling centres
(EE-waste can also be delivered at stores retailing EE-products).
The uncertainty analysis focused on the fractions collected
from households and delivered to glass/metal recycling, while
source-separated garden waste, textiles, EE-waste and wood were
left out of the calculations, as was bulky waste delivered to the
recycling centres. We assumed a three-bin system in addition to
collection points for glass and metals. The waste was assumed
source-separated into the following fractions: (1) mixed waste,
(2) paper and cardboard, (3) plastic, and (4) glass and metals
(Fig. 1). Sorting of food waste has been implemented in only some