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Landfill Biodegradation Of Foam Compositions Based On Polymers Not Inherently Biodegradable (2)
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Landfill Biodegradation Of Foam Compositions Based On Polymers Not Inherently Biodegradable (2)

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  • 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 [1]. Moisture content varies from Eubacterium and Cellulomonas [9]. No “standard” about 15 to 45% [2]. 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 [3]. sheet [10]. 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 [3]. Pseudomonas putida, strain KT2442, has been bred to The use of distilled water in an actual landfill is very consume petroleum spills [4]. 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 [5]. 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 [10]. Anaerobic microbes predate the Paleozoic oxygen explosion [6]. 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 [7] In the above example, BIOchem C-3™, a or even metal oxides [8]. 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 [1]. 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 [11]. 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% organotitanate catalyst 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 [3]. 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 [12]. 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 landfill. 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 to power a useful circuit, for example, to monitor or operate methane recovery from the landfill. 1. Municipal Waste Disposal in the 1990’s, B.G. Liptak, Proprietary PVC formulations have been developed Chilton Books, Radnor, PA, 1991, p 26-39. for commercial signage called BIOflex using subject 2. J.A. Scher, Chem. Eng. Progress, 67(3), 81-84 (1991). additive. Figure 7 shows the landfill decomposition of 3. R.F. Grossman, J. Vinyl & Additive Tech., 14(3) BIOflex Vinyl under ASTM D5526 landfill conditions 110-112 (2008). of 30°C at 50% moisture. 4. N.C.M. Gomes et al, Microbiol. Ecology, 54(1), 21-33 (2005). 5. R.F. Grossman, unpublished results. 6. P.D. Ward, Out of Thin Air, P.D. Ward, Joseph Henry Press, Washington, DC, 2006, p 38-42. 7. J.D. Coates et al, Nature, 411, 1039-1043 (2001). 8. D.R. Lovley & D.J. Lonergan, Appl. Environ. Microbiol., 56(6), 1858-1864 (1990). 9. A.C. Palmisano & M.A. Barlaz, Microbiology of Solid Waste, CRC Press, 1996, p 49-72. 10. R.F. Grossman, J.E. Schleicher, Jr. & L. D’Alessio, J. Vinyl & Additive Tech., 13(3), 132-135 (2007). 11. R.F. Grossman, US 7,390,841 12. R.A. Alberty, Thermodynamics of Biochemical Figure 7 Reactions, Wiley, 2003, p 162.