International Review of Waste Management Policy - Department of ...

536
29/09/09
• Second, the fact that the blue line falls slightly in the second year indicates
that some garden waste – but rather less than the total collected - is
diverted from residual waste collection in addition to material that may
have been diverted from existing management options. However, it is
arguable in this case that much of the reason for this material being
disposed in the first year was due to the zero cost nature of UK residual
waste collection services. This type of activity is more effectively
discouraged where PBU systems are in place;
• Third, and most importantly, the data for the second year shows the
seasonal nature of garden waste generation. In the UK the growing season
and active gardening period runs through the warm spring and summer
months with generation falling nearly to zero through the winter. A similar
seasonal pattern might be expected in Ireland.
Figure 33-1: Waste Arisings Before and After Free Garden Waste Collection in a UK
Municipality
Tonnes Collected
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
-
Limited trial of
free garden waste
collection service
Apr-02
May-02
Jun-02
Jul-02
Aug-02
Sep-02
Oct-02
Nov-02
Dec-02
Jan-03
Feb-03
Month
Full coverage
of free garden
waste
Mar-03
Apr-03
May-03
Jun-03
Jul-03
Aug-03
Sep-03
Oct-03
Nov-03
Dec-03
Jan-04
All Waste Excl Kerbside Garden
All Waste Incl Kerbside Garden
Although food waste does not tend to exhibit observable seasonality, the variable
pattern in garden waste generation has implications for the treatment systems
operated. This is especially the case where food and garden waste are collected
together. Seasonal garden waste generation will mean that the relative concentration
of food to garden waste will vary throughout the year. This can make it difficult to
optimise the treatment system and will also have a potentially negative impact on
treatment economics since capacity has to be provided for peak flows, potentially
giving rise to redundancy in treatment capacity. We explore this issue further in the
following subsection.
Experience also highlights the fact that food waste is often captured rather poorly by
systems which focus principally on garden waste, particularly where the collection of