1. Landfill Biodegradation of Foam Compositions Based on Polymers
Not Inherently Biodegradable
By R. F. Grossman, Ph.D.
Abstract lack of specialization, low energy diet and reproduction
through division leads these species to have an appetite
A variety of anaerobic landfill microbes are shown to be for almost anything organic.
able to metabolize expanded polystyrene and polyvinyl
chloride foam compositions containing organotitanate or Experimental
organozirconate additives that provide hydrophilic points
of attack, but do not catalyze degradation during service Landfills used were based on the guidelines of ASTM
in an aerobic environment. D5526 and comprised 90% sterilized sewage (available
commercially as Milorganite ®), plus 10% actively
Background fermenting compost. Such compost is likely to contain a
number of methanogenic bacteria. A number of species of
The interior of a landfill is dark, warmer than ambient and Methanobacterium have been identified, as well as
low in available oxygen . Moisture content varies from Eubacterium and Cellulomonas . No “standard”
about 15 to 45% . At the lower level, not even food compost is available and the extent of microbial variation
waste will biodegrade. The most prevalent ingredient, is largely unknown. This factor introduces a similarly
often 40-50%, comprises paper products; plastics tend to unknown potential for inconsistency. The above mixture
run 1-5% (1). Cellulosics such as paper degrade poorly at was adjusted to 40-45% moisture. Landfills of this type
moisture levels below 50-60%, which are rarely reached have been shown to consume plasticized PVC film and
in commercial landfills . sheet . Although ASTM D5526 calls for use of
distilled water, water from a local pond was used. This
A variety of the aerobic, Gram-negative bacterium eliminates the delay before microbial attack begins .
Pseudomonas putida, strain KT2442, has been bred to The use of distilled water in an actual landfill is very
consume petroleum spills . It can also consume unlikely.
expanded polystyrene (EPS), but Pseudomonad bacteria
are (to date) obligate aerobes and have no anaerobic An important factor in the utility of common plastics
capability . Aerobic microbes typically favor sexual is their water resistance, that is, their hydrophobic
reproduction; if food levels become inadequate, they form character. Part of that utility is the defeat of attack by
spores to provide the next generation and die. They are, microbes under ordinary conditions. It was discovered
therefore, modern. A number of bacteria can function that a class of additives can be employed to produce
either aerobically or anaerobically; examples include hydrophilic attachments to points on hydrophobic
Staphylococcus and E. coli. polymers which enable anaerobic but not aerobic
microbial attack .
Anaerobic microbes predate the Paleozoic oxygen
explosion . The emergence of cyanobacteria capable of
photosynthesis may have been a significant factor in the
development of the oxygen-rich atmosphere. In addition
to archaeans and bacteria, microbes capable of anaerobic
metabolism include many algae and molds. In the absence
of atmospheric oxygen, food is metabolized using
oxidizing species such as phosphates, sulfates, nitrates  In the above example, BIOchem C-3™, a
or even metal oxides . The free energy available from pyrophosphato titanate chelate quat is shown wherein R =
fermentation or other anaerobic metabolic paths is low methyl, R’ = propyl. More specifically, the additive can
compared to aerobic oxidation . The combination of be described as a Di(dioctyl)pyrophosphato ethylene
2. titanate (adduct) N-substituted methacrylamide or a
Titanium IV bis(dioctyl) pyrophosphato-O (adduct) 2 Results and Discussion
moles N, N-dimethylamino-alkyl propenoamide or
Titanate (2-), bis [P,P-dioctyl diphosphato (2-)-кO΄΄, After 21 days in an anaerobic landfill, samples of EPS
кO΄΄΄΄][1, 2-ethanediolato (2-)-кO, кO΄]-, dihydrogen, containing 1% of either the above or similar
branched and linear, compound with N-[3- organotitanates showed flourishing microbial colonies
(dimethylamino) propyl] -2-methyl -2-propenamide (1:2) and loss of sample mass – see Figure 2.
bearing CAS # 198840-66-3. Analogous neoalkoxy
organotitanates and organozirconates are also effective
In the following experiments, 5 g of EPS (Joy Sports &
Leisure, China) or vinyl foam (3M) were dissolved in 25
ml MEK at room temperature and 50 mg of the above
catalyst added – see Figure 1. The solution was allowed to
evaporate in an aluminum pan and 2 g added to 50 g of
the above landfill in a Petri dish, which was then sealed
with several wraps of 3M #33 electrical tape.
Figure 2 – Catalyzed EPS Is Attacked Rapidly After
Several Weeks Into Test (at 10x). Microbial Colonies
Are Doing Well, Notable Loss of Mass - Dense
Samples Much Slower
After 90 days, these samples had almost completely
vanished into the biomass. Control samples were
unaffected – see Figure 3.
Figure 1 – ASTM D5526 Simulated Landfill:
Landfill = 90/10 sterilized sewage/active compost,
40-50% moisture, 30-35°C, dark incubator, sample ~
5% of landfill mass.
Sample of an EPS article containing 1%
Gas evolution was measured using micro-
manometers supplied by Carolina Biological. Gas evolved
from 10 g landfill, with or without foam samples, was
measured versus time. Landfills included controls and
those to which cultures had been added. The latter
included Protococcus, Spirulina, Spyrogyra and Cyathus
algae; Chlamydomonas, Anabaena, Fischerella and Figure 3 – After 3 Months
Eucapsis cyanobacteria and the archaean Halobacterium Very Little EPS Left, Colonies Are Dying Back
sp. NRC-3. Gas evolution was also measured using a
landfill that had previously consumed PVC plastisol Vinyl foam samples behaved similarly, except for
based on Geon 121A, with 60 phr DINA and 1 phr leaving small quantities of filler and pigment. Again,
titanate catalyst . Here the sample was either the same control samples showed no effect other than slight
PVC compound, PVC foam or EPS. microbial colonization at the sample edges – see Figure 4.
Experiments using 10 g micro landfills as microbial Note: The foam formulation used 1phr the BIOchem
fuel cells were carried out with a University of Reading C-3™ coupling agent in a typical AZO recipe, urea
(UK) kit. Landfills were kept at 30-35°C using a Boekel activation employing a tin carboxylate stabilizer. Since
Scientific Model 132000 Incubator. the additive functions by enabling microbes to consume
plastics, biocides will inhibit effectiveness. For example,
zinc-based stabilizers inhibit landfill biodegradation
because they are known biocides. Tin carboxylate
3. stabilizers will not interfere with the biodegradation the presence of the above cultures, with those that
mechanism. lowered gas yield, addition of EPS appeared to lower gas
yield slightly more. Addition of 0.4 g plasticized PVC
Phthalocyanine pigments will also inhibit landfill
foam containing catalyst had a similar effect.
biodegradation and should be avoided. In polyolefins,
color forming antioxidants, such as BHT and Bisphenol, Use of a landfill that had previously consumed PVC
should be avoided in favor of high efficiency stabilizers, plastisol increased the rate of gas evolution when a
such as Irganox® 1010. second sample was added. A third experiment did not
provide a further increase. A landfill that had consumed
PVC plastisol also increased the rate of gas evolution
when a PVC foam sample was added, but had no effect on
the gas evolution during EPS consumption. The converse
was also found: a landfill that had consumed EPS did not
increase the rate of gas evolution from degrading vinyl
foam. It is likely, therefore, that microbial modifications
required to metabolize plastics in an anaerobic
environment are, at least in some cases, heritable.
The above observations suggest that the protocol of
ASTM D5526 and related standards where gas evolution
is taken as the measure of biodegradation may be
thoroughly misleading. The observations that are
significant are that an object placed in a landfill supports
Figure 4 – Vinyl Foam, 3 Weeks In Landfill microbial colonization and ultimately vanishes.
Gas evolution began within a few hours – see Figure Addition of 10 g of the above landfill to the cathode
5. A 10 g ASTM D5526 type landfill yielded 0.2 ml gas compartment of the University of Reading microbial fuel
in 24 hours and 0.7-0.8 ml in 72 hours. If the landfill cell (MFC) with 5% Fe (II)/Fe (III) ammonium sulfate
contained a culture of Spirulina, Spyrogyra, Anabaena or solution in the anode compartment to mediate air
Fischerella, gas evolution was reduced to 0.1-0.3 ml after oxidation generated 240-250 mV output – see Figure 6.
72 hours, increasing slowly to 0.5-0.7 ml after 21 days. This is reasonable in view of methanogenesis half cell
Cyathus and Eucapsis had no such effect. On the other reports .
hand, landfills containing Protococcus or Halobacterium
did not evolve gas. In these cases, the product of
anaerobic metabolism may be bicarbonate ion. Those
landfills that did not evolve gas had become slightly
alkaline; those evolving methane and carbon dioxide
remained at their original pH, about 6.5.
Figure 6 - Landfill Battery: Landfill + Sample
Supplying 321 mV vs. Fe(II)/Fe(III) Mediated
Reduction of O2
With a sample comprising 9 g landfill and 1 g EPS,
the output, tested daily, rose over 21 days to about 320
mV, then slowly retreated to the original level. It seems
likely, therefore, that the sample provided a higher energy
Figure 5 – Gas Evolution From The Landfill
food source to the anaerobic feeders in this particular
Addition of 0.4 g EPS containing organotitanate
catalyst increased the gas yield of the landfill slightly. In The current output of 10 g of the above landfill was
4. about 0.05 mA. A unit of several tons would be required References
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