The decomposition of paper
products in landfills
FABIANO XIMENES
Industry and Investment NSW P.O. Box 100,
Beecroft, NSW, 2119, Australia
INTRODUCTION
It is estimated that in 2006/2007 approximately
1.5 million tones of paper were disposed off in
landfills in Australia (Department of the
Environment, Water, Heritage and the Arts
2009). Worldwide, it is estimated that more
than half of the mass of paper destined for
disposal is eventually disposed off in landfills
in most industrialized countries (Subak and
Craighill 1999). The decomposition of organic
materials under anaerobic conditions in
landfills results in the generation of carbon
dioxide and methane (a powerful greenhouse
gas), in approximately equal proportions. The
Federal Department of Climate Change (DCC)
has adopted a default decomposition factor (or
DOCf – fraction of degradable organic carbon
dissimilated) of 0.5 for all organic materials
placed in landfills (DCC 2008). This factor is
designed to be applied to the total volume of
organic waste, and therefore is clearly not
applicable to individual organic fractions in the
waste stream. Organic materials such as food
residues decomposition to a much greater
extent than other materials. Using the DCC
default
decomposition
factor,
the
decomposition of wood products and paper in
landfills accounts for 50% of the waste sector
emissions, or 1.5% of the national greenhouse
gas emissions.
This paper will discuss the current status of
knowledge on the decomposition of paper
products in landfills, with special attention to
work currently conducted in Australia and in
the USA. The implications of the latest
findings on a number of important policy areas
(emissions trading, waste management,
greenhouse footprint of products) will also be
discussed.
PAPER IN LANDFILLS AND
RECYCLING
Although there are varying estimates of
volumes of paper disposed of in landfills, they
all indicate that paper products represent a
significant component of the overall waste
stream, despite the fact that the level of
recycling of at least some types of paper in
Australia is amongst the highest in the world.
The following information is contained in a
recently released report from the Australian
Government (Department of the Environment,
Water, Heritage and the Arts 2009).
Municipal solid waste (MSW).
In 2006–07, an estimated 7.3 million tonnes of
MSW were disposed of to MSW landfills in
Australia, of which paper and cardboard
accounted for 1.9 million tonnes. If
consumption, disposal and recycling rates
remain the same, it is predicted that by 2020
the amount of paper and cardboard disposed
off in the MSW stream will be in the order of
3.5 million tonnes.
Commercial and Industrial (C&I)
In 2006–07, an estimated 6.4 million tonnes of
C&I waste were disposed of to C&I landfills in
Australia, of which paper and cardboard
accounted for 3.5 million tonnes.
Construction and demolition (C&D)
In 2006–07, an estimated 7.1 million tonnes of
C&D waste were disposed of to C&D landfills
in Australia, of which paper and cardboard
accounted for 0.2 million tonnes.
Paper therefore accounted for 5.6 million tones
of waste going into landfill in 2006/07, or
27.1% of the total amount of landfilled
material in Australia. Wood and green organics
accounted for 2.5 million tones or 12% of the
total. It is important to note that many landfills
in Australia collect methane to generate
electricity. As at 2007, there were 58 landfill
gas generation plants in Australia with a
capacity totalling 165.3 MW. Australian
landfills captured 26% of landfill gases in
2005–06 (Department of the Environment,
Water, Heritage and the Arts 2009). In a recent
assessment conducted for Hanson landfill
services and the City of Whittlesea in Victoria
(Hyder Consulting 2010), it was estimated that
paper and cardboard accounted for 22% of the
total methane potential of the volume of waste
deposited in 2008 at the Wollert landfill site.
Most landfills typically generate significant
volumes of methane for between five and
twenty years after the waste is buried (Suflita
et al 1992).
Paper recycling
The recycling rate for paper packaging was
estimated at 56% in 2007. The quantity going
to landfill had decreased by about 23% from
2003, despite increased generation of
packaging waste. Approximately 76% of
newsprint was recycled in 2007, a diversion of
over 500,000 tonnes of paper from landfill. All
states recycle paper and cardboard from the
municipal waste stream with an estimated
940,000 tonnes recycled in 2006–07. Not all
states collect data on paper and cardboard
recycling from the commercial and industrial
waste sector. An estimated 863,000 tonnes
were recycled in Victoria, South Australia,
Western Australia and the Australian Capital
Territory in 2006–07. It is important to note
that the same fibre can only be recycled a
limited number of times.
Given the comparatively short service life of
most paper products, the same fibre that has
been recycled two or three times may be
disposed off in landfills only ten or fifteen
years following its use as virgin fibre (if the
fibre is not used for a different purpose such as
burning for energy generation). Therefore, the
landfill stage of the life of most fibres is
ultimately what will determine the longevity of
the carbon in paper products.
REVIEW OF STUDIES ON THE ISSUE
OF DECOMPOSITION OF PAPER IN
LANDFILLS
The number of studies addressing the issue of
the decomposition of paper products in
landfills, both field-based and laboratorybased, is limited. There have been numerous
anecdotal reports of paper products recovered
from landfills after a long-period of burial (e.g.
Kinman et al., 1990; Bogner, 1990; Rathje and
Murphy, 1992, Walsh and LaFleur 1995).
Ximenes et al (2008) recovered large volumes
of a range of paper products from two sites at
one landfill in Sydney. The samples, which
had been buried for between nineteen and
twenty-nine years, included newspapers,
magazines, telephone books, cardboard and
office paper (Figure 1).
However, only a few studies have attempted to
quantify decomposition of paper in landfills. In
one of the earliest contributions (Bingemer and
Crutzen 1987) it was suggested that paper
products degraded entirely within 5-20 years of
placement in landfill. This was based on
theoretical stoichiometric models. Other
authors
have
attempted
to
quantify
decomposition from samples retrieved from
real-life landfills. Baldwin et al (1998) buried
samples of newspaper and filter paper in a
landfill and periodically sampled the sites over
6 years for analyses. Three sites were chosen
representing different climatic conditions.
Very little filter paper was recovered from one
of the sites, in contrast to the other sites where
little decomposition was observed. Total loss
of mass for newspapers was generally
insignificant - only in the wettest site was there
a loss of 17% mass after 2 years. There was a
strong correlation between mass loss and lignin
content; an increase in lignin content from 0 to
25% reduced total mass losses from 95 to 15%.
Chen et al (2004) analysed the decomposition
of 15-30 year old excavated newsprint
samples, with the aim to detect any changes in
the lignin structure of the samples. The lignin
concentration of the landfill samples was
higher than that of fresh control samples,
suggesting some decomposition of the
carbohydrate portion of the samples had taken
place.
Figure 1. Examples of paper products
recovered from Lucas Heights landfill in
Sydney after 19 years of burial
Micales and Skog (1997) conducted an
analysis of the likely decomposition of a range
of forest products based on results from
commercial methane recovery models. They
estimated a total mass loss of 15.7% of
newspaper, 17.5% of coated paper 31.5% of
cardboard boxes and 38.2% of office paper in
landfills.
Laboratory studies make it possible to control
key variables affecting decomposition in
landfills (i.e. temperature, moisture content,
nutrient availability and microbial presence).
Thus, results of such studies represent the
ultimate biodegradability of specific waste
types, and are very unlikely to be observed in
excavated landfill samples, as ideal
decomposition conditions are very rarely if
ever observed in real life landfills. They can be
adopted in the absence of conclusive fieldbased factors, with the understanding that they
overestimate the rate and extent of
decomposition for some organic materials .
Professor Morton Barlaz (North Carolina State
University) and his research group have
published numerous papers on decomposition
of organic materials in landfills, and the US
EPA has adopted his results for greenhouse
reporting purposes. In an early study (Eleazer
et al 1997), a number of paper products made
in the USA were shredded and placed
underanaerobic conditions in small reactors
simulating landfill conditions (with sufficient
moisture, nutrients and microbial presence to
allow maximum decomposition). Office paper
had the most extensive cellulose depletion, and
newsprint the lowest (27%). In a more recent
report (Barlaz 2004), carbon storage factors
(defined as the fraction of the carbon in the
original product that is sequestered in landfills)
are provided for a number of paper products.
They vary from 0.12 for office paper to 0.84
for newspapers, with corrugated boxes and
coated paper having carbon storage factors of
0.61 and 0.79, respectively.
CURRENT WORK
More recent research conducted both in
Australia and in the USA strongly suggests
that the currently adopted DCC default
decomposition factor when applied to paper
products in landfills overestimates their
greenhouse emissions. The extent of the
overestimation is typically linked to the lignin
composition of the paper – the higher the
lignin
composition,
the
lower
the
decomposition observed. This section of the
paper will discuss the latest field-based and
laboratory results on the decomposition of
paper products in landfills.
As mentioned earlier, large volumes of a range
of paper products have been recovered from
excavations conducted in both closed and
operational MSW (Municipal Solid Waste)
landfills in Sydney (Figure 2). The landfill
sites included Lucas Heights, Sydney Park,
Meadowbank and Eastern Creek. Newspapers,
magazines, books, telephone books and office
paper have all been recovered and
characterized for moisture content, apparent
density and chemical composition. Initial
visual observations suggested most samples
were remarkably sound, although extremely
wet (typically the moisture content of samples
was above fibre saturation point) and
physically damaged by the use of heavy
machinery and high compaction in landfill
operations. The samples were then dried and
ground prior to chemical composition analyses
(cellulose,
hemicellulose,
lignin,
ash,
extractives).
Figure 2. Typical profile of a MSW landfill
cell (Eastern Creek landfill, Sydney)
Samples that were easily dated (newspapers,
telephone books, magazines, paperbacks) were
preferentially selected for analyses as in most
cases it was possible to source exact matching
controls. For example, if a Sydney Morning
Herald from April 12, 1990 was recovered, we
were able to source a copy of the same
newspaper from exactly the same day (or same
month if necessary). This provided a perfect
opportunity to quantify any carbon loss from
the landfill samples by comparing any changes
in their chemical composition to those
observed in control samples. The same level of
rigour could not be applied to samples that
were difficult to match with pre-existing
controls, such as more obscure publications
(e.g. Western Sydney Business Review, 1990),
office paper and computer printouts without
dates. For these samples all attempts were
made to source samples of the same type of
paper corresponding to the same time of burial.
This represents a suitable method for analyses
of paper products recovered from landfills, as
unlike solid wood products, the chance of any
significant decomposition happening to the
paper products during their service life (i.e.
prior to burial in landfills) is low. Any
significant decomposition during their service
life would constitute a confounding factor in
the analyses, as not all decomposition would
have contributed to methane generation.
Therefore, results of analyses from excavated
samples can be more easily correlated with
those from laboratory experiments.
A preliminary analysis of the chemical
composition results for the most recent
excavation (Eastern Creek site) suggests
minimal decomposition after a period of burial
ranging from 6 to 18 years. The full results of
the research will be published in more detail in
a future manuscript.
A recent joint research study between
Australian and US researchers assessed the
biodegradability and methane yield of different
types of paper products under controlled,
optimum decomposition conditions. The
research methodology was similar to that
described earlier (Eleazer et al 1997), where a
number of paper products were shredded and
placed in anaerobic conditions in small
reactors simulating landfill conditions (with
sufficient moisture, nutrients and microbial
presence to allow maximum decomposition).
The percentage of carbon emitted from the
various paper products as greenhouse gas
ranged from 5-45% depending on the paper
type (the full results of this research will also
be published in more detail in a future
manuscript). As discussed earlier, these figures
are very unlikely to be observed in excavated
landfill samples, as actual decomposition from
real-life landfills should be lower. In fact, a
preliminary comparison of the results from the
research projects described above clearly
suggests that, for the same paper product,
higher levels of decomposition are measured
for the “laboratory” sample compared with the
“landfill” sample. It is possible though that
more decomposition may take place after
eighteen years of burial in landfill, which could
potentially bring the results closer. More
analyses of paper samples buried for longer
periods of time is required to allow a proper
comparison of the results.
Several factors may contribute to low
decomposition observed in previous studies,
such as moisture, pH, temperature as well as
bioavailability
(Barlaz
2006).
High
concentrations of sulfate, nitrate, iron and
manganese may inhibit bacterial action.
Gurijala and Suflita (1993) reported that most
of the paper samples collected from a landfill
were covered with sulfate, absorbed probably
from
gypsum-based
construction
and
demolition debris. Ink may also play a part in
the inhibition of decomposition. In previous
studies by Cummings and Stewart (1994 and
1995), it was observed that coating of filter
paper with ink halved the activity of bacteria.
The ink layer appeared to have masked the
cellulose fibres, and bacteria were detected in
cellulose fibres exposed by breaks in the ink
coating. However, Wu et al (1992) did not
observe any difference in the rate and extent of
degradation of newsprint due to the presence
or absence of ink. The observed level of
decomposition was low for all newsprint types
tested.
The effect of wood type used in the
manufacture of paper may also warrant further
research. Preliminary results from the current
laboratory work suggest that the wood type
may play a significant role in the
decomposition of paper, particularly for paper
types that would be expected to show higher
levels of decomposition (i.e. papers with low
lignin content). Other factors to consider may
include the effect of recycled fiber use versus
virgin pulp and the effect of different types of
filler .
POLICY IMPLICATIONS
Research on the decomposition of paper
products in landfills may have significant
implications for important policy areas such as
emissions trading, waste management and the
comparison of the greenhouse footprint of
products.
Emissions Trading
Results of the research described above
suggest that there is potential for sectors of the
paper industry to claim a long-term carbon
storage factor for the carbon in paper that ends
up in landfill. It is possible that a long-term
storage factor for paper products will be
ultimately determined by the lignin
composition of the paper, which in turn is also
correlated with the manufacturing process
(mechanical or chemical pulping). The results
of the recent research described earlier make a
strong case for recognition of long-term
storage of carbon in paper products,
particularly those with a high lignin
concentration. Obviously any methane
emissions from the same products would also
have to be accounted for. It is important to note
that modern landfills collect and burn methane
to produce electricity for the grid. In a recent
report (Hyder Consulting 2010) it was
estimated that the collection efficiency of
methane was between 68 to 94% at a modern
landfill in Victoria.
A mechanism would need to be devised for
inclusion and recognition of carbon storage in
paper products in the design of any future
Emissions Trading Scheme. Issues that would
need to be considered would include:
 Credit / liability ownership (forest
grower,
pulp
and
paper
manufacturers,
printers,
landfill
operators?);
 Which products to include – would
imported and exported pulp and paper
products
be
excluded
from
accounting?;


Origin of the feedstock – how to
ensure that the resource used for the
manufacture of the paper originated
from eligible forests;
Auditing requirements / proof of
permanence – need for robust datasets
to satisfy strict auditing requirements
and which can demonstrate that the
carbon in the products is stored for
the minimum timeframe required
(typically between 70-100 years for
carbon accounting).
Waste Management
The greenhouse benefit of the diversion of
specific components of the waste stream such
as paper products from landfills is often
calculated
using
the
DCC
default
decomposition factor for organic materials in
landfills. The avoided landfill emissions
calculated in this fashion are significantly
overestimated by the adoption of the DCC
default decomposition factor for most types of
paper products. As mentioned earlier, adoption
of a single default decomposition factor for all
organic materials in landfills may be suitable
for estimation of emissions from all organic
materials in landfills. However, it was not
designed to be applied to specific components
of the waste stream such as paper products. If
the aim is to achieve real reductions in
greenhouse gas emissions, it is critical to base
any assessment of the greenhouse intensity of
different processes on credible science.
Otherwise, there is a real risk perverse
environmental outcomes will be created. Grant
et al (2000) showed that the choice of different
decomposition factors for paper products in
landfills and acknowledgement of carbon
storage can reduce the greenhouse gas benefits
of recycling by up to 50%.
Greenhouse footprint of products / Life
Cycle Assessments (LCAs)
For Life Cycle Assessments (LCAs) of paper
products that include disposal within their
scope, the adoption of lower decomposition
factors for paper in landfills may significantly
alter the greenhouse footprint outcomes of
different products. For instance, greenhouse
comparisons between e-paper (billing, online
media, etc...) and their printed counterparts
may be significantly impacted by the
decomposition factor adopted. As mentioned
earlier, more than five million tonnes of paper
products are disposed of in Australian landfills,
even though our recycling rates at least for
some types of paper are amongst the highest in
the world. The greenhouse footprint of those
products that end up in landfill will be
significantly impacted by the decomposition
factor adopted.
CONCLUSIONS
Despite the large volumes of paper reaching
landfills each year, minimal research has been
conducted on the decomposition behaviour of
those products under the anaerobic conditions
that prevail in landfills. Recent experimental
research and research conducted on excavated
samples from landfill strongly suggest that a
significant proportion of the carbon in a range
of paper products can be considered to be
stored for the long-term. These results indicate
that paper products may play an important role
in emissions trading, and also highlight the
importance
of
using
less
generic
decomposition factors when estimating
avoided emissions from diverting paper from
landfills.
ACKNOWLEDGMENTS
Thanks to Rebecca Coburn for her help editing
the paper.
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