APPENDIX 2: A CRITIQUE OF MUNICIPAL WASTE DATA
The composition of municipal waste arisings in the
UK is known at best poorly. The data used by DETR in Waste
Strategy 2000 are shown in Table 1, and though no source was
quoted, they appear to have been based upon old data from the
National Household Waste Analysis Programme (NWHAP) carried out
at the start of the 1990s. This data may be of limited use. Quite
apart from the fact that the data refers to bin waste arisings
only as opposed to municipal waste as a whole (i.e., less than
two-thirds of the total stream - see above), the actual methodology
used in the NHWAP has been the subject of some criticism. For
example, the lack of significance accorded to sampling dates may
have biased results from samples, and the fact that materials
may have been mixed together, so transferring mass from 'wet'
to 'dry' fractions, will have influenced the weight ascribed to
a specific fraction.
Table 1: Waste Composition Data used by DETR/NAW
and in Environment Agency Demonstration Disk for Wisard
Quite apart from the fact, therefore, that one would
expect street litter, bulky collections, CA waste arisings and
other contributing wastes to have a composition different to bin
waste, the limitations of the approach undertaken imply that this
data is unlikely to constitute an adequate basis upon which to
base waste planning decisions. Furthermore, the fact that the
base data is now so dated forces one to ask questions concerning
the evolution of composition over time. This is something we know
relatively little about.
Compositional data are important in understanding
which materials are available in which quantities for diversion
through recycling and composting. Indeed, ideally one requires
a more detailed breakdown (than that given by DETR/NAW, itself
supplied by the Environment Agency) if one is to assess accurately
the suitability of materials for recycling, composting, energy
from waste incineration and other waste treatment options. An
even finer resolution in the characterisation of waste is required
if one is to seek to understand the merits of pursuing materials
reduction (in industry) as a strategy for minimising waste at
the household level. This would be required to improve understanding
of how to minimise wastes associated with specific products.1
The discussions around composition are by no means
trivial ones. They can skew strategies in one direction or another
since they suggest what is and is not feasible in terms of different
waste treatment methods. Under the Landfill Directive, the biodegradable
components of the municipal waste stream are most important. These
* Paper and card;
* Nappies; and
DETR estimated that these constitute 62% of all wastes.
Note once again, however, that these data referred only to household
waste as opposed to all municipal wastes.
Whether this figure is 'correct' is difficult to
know. It may be that it is a good estimate for the total fraction
(though as mentioned above, some feel it is too low), but the
breakdown of that fraction is as important as the total figure.
In the DETR/NAW work, the breakdown of this biodegradable fraction
is such that the proportion that is paper is larger than the proportion
that is putrescible. Other work suggests that the opposite may
be the case. Furthermore, European data on composition seems to
confirm this. Alongside other countries, the UK data appears rather
off with the putrescibles fraction very low. The different breakdowns
suggest different strategies.
For these reasons, waste composition data is a matter
of considerable debate. In particular, in the wake of the publication
of A Way With Waste (the consultation draft of the England and
Wales Strategy), many disputed the compositional data being used,
especially in respect of what were believed to be low figures
for the putrescible fraction. Network Recycling comments that
all of their most recent domestic waste audits (bin waste) have
found a putrescible content of at least 30 % (putrescible meaning
kitchen and garden waste, and not including other types of biodegradable
waste as defined in the Landfill Directive). Recent waste analysis
work conducted in six areas in South Gloucestershire found that
the average putrescible content of the waste stream was 39 % (range:
34 % 56 %). Sampling in Brixworth (for Waste
Watch) gave a putrescibles figure of 49%. Ecologika report on
seventeen waste analyses carried out in London. The average figure
for compostables (again excluding paper) quoted is 38%.
Other individuals we have spoken to suggest that evidence increasingly
points to a percentage figure in the high 30's. This raises the
question as to whether the data used in Waste Strategy 2000
is sufficiently robust to base a strategy upon.
All of these comments refer to bin waste only. It
is true, of course, that if one seeks to separately collect (as,
for example, in Brixworth) compostables in Brown Bins, one may
draw out more putrescible material into bins that might otherwise
have gone elsewhere (i.e. CA sites, or home composting). However,
this may make the collection more representative of total wastes
(as opposed to just bin wastes).
As regards CA site wastes, two similar sets of data
are shown in Table 2. Relatively few studies have been carried
out on CA waste composition (and even fewer on street litter etc.).
Yet materials delivered at CA sites may be very easily separated,
and much of the material, including inert construction materials
(presumably, a major part of the DIY noncombustible fraction),
and wood (which is frequently lumped into the 'miscellaneous combustibles'
category, even though wood packaging is now covered by the Packaging
Regulations), may be suitable for reuse, recycling and composting.
Again, the putrescibles fraction is of the order 40%.
Table 2: Results of Two Studies Concerning CA Site
|University of Luton
|CA Waste Samples||CA Waste Samples
|Paper and Card||3.0%||Paper (newspaper)
|Paper (other)||Paper (other)
|Glass (flat)||Glass (flat)
|DIY combustible misc||5.0%
|Garden Waste||38.4%||Garden non-combustible
|Garden (grass)||Garden (grass)
|Garden (branches)||Garden (branches)
|Sump oil||0.1%||Motor Oil
Much better data is needed on composition than we
have at present. The Environment Agency is due to commence shortly
the next stage of the National Household Waste Analysis Programme.
Dr Dominic Hogg, March 2001
This is helpfully
displayed in Parfitt et al (1997) A Review of Household Waste
Arisings and Compositional Data, DoE Wastes Technical Division,
R&D Report P240.
Rachel Jarrett, Network Recycling.
ReInventing Waste: Towards a London Waste Strategy, London:
Ecologika for LPAC and the Environment Agency.