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Kolstad J.J.,NatureWorks | Vink E.T.H.,NatureWorks | De Wilde B.,Organic Waste Systems NV | Debeer L.,Organic Waste Systems NV
Polymer Degradation and Stability | Year: 2012

Ingeo™ polylactide (PLA) 1 biopolymers are used world-wide in a diverse range of applications and, after the useful life of the particular application, they can be recycled (either mechanically or chemically) or disposed of via various end-of-life options, such as composting, incineration and landfilling. The use of compostable materials for food packaging could be an enabling technology to allow the diversion of food waste from landfills into composting facilities. However, despite many new initiatives and existing programs it is still true that a significant part of industrial and household waste still ends up in landfills. Because polylactide polymers are known to be compostable the question is often raised about the behaviour of these materials in landfills. In order to study the behaviour of Ingeo polylactides (PLA) in landfills two studies were performed aimed at generating reliable information on the anaerobic biodegradation of PLA under conditions of extended time and modest temperatures. The first test (under accelerated landfill conditions) was done at 21°C, and three moisture levels, extending to 390 days and the second test (a high solids anaerobic digestion test under optimal and significantly accelerated conditions) was conducted at 35°C for 170 days. Each test is meant to represent an accelerated test of what could happen under anaerobic landfill conditions. These two tests each had accelerated the biological degradation sufficiently that they were in some sense equivalent to approximately a century of a "typical" biologically active landfill. The semicrystalline polylactide samples did not produce a statistically significant quantity of biogas during either test. The amorphous PLA did generate a small amount of biogas in the test at 35°C, but none in the test at ambient temperature. Here it should be noted that the tests were conducted under accelerated, optimal landfill conditions, the biodegradation was observed in a 100 year timeframe and the market volume of amorphous PLA is low. We conclude that semicrystalline PLA (typical of >96 wt% of resin used to manufacture products), under anaerobic biological conditions typical of a landfill at moderate temperatures (where PLA hydrolysis is slow), will not lead to significant generation of methane, and that no significant population of organisms is available under anaerobic conditions to directly degrade high molecular weight PLA. Because there was no direct biological degradation of PLA under the anaerobic conditions, it is likely that any degradation of PLA in a landfill would require a chemical hydrolysis step prior to any biodegradation, which is analogous to the situation in aerobic composting. At 20°C this process is estimated to take 100+ years, and under those conditions the degradation of the PLA would be extremely low. Additional data on the time/temperature history experienced in landfills will be needed to understand the net effect for disposal of PLA globally. © 2012 Elsevier Ltd. All rights reserved.

Raposo F.,CSIC - Instituto de la Grasa | Fernandez-Cegri V.,CSIC - Instituto de la Grasa | de la Rubia M.A.,CSIC - Instituto de la Grasa | Borja R.,CSIC - Instituto de la Grasa | And 17 more authors.
Journal of Chemical Technology and Biotechnology | Year: 2011

Background: This paper describes results obtained for different participating research groups in an interlaboratory study related to biochemical methane potential (BMP). In this research work, all experimental conditions influencing the test such as inoculum, substrate characteristics and experimental conditions were investigated. The study was performed using four substrates: three positive control substrates (starch, cellulose and gelatine), and one raw biomass material (mung bean) at two different inoculum to substrate ratios (ISR). Results: The average methane yields for starch, cellulose, gelatine and mung bean at ISR of 2 and 1 were 350 ± 33, 350 ± 29, 380 ± 42, 370 ± 36 and 370 ± 35 mL CH4 g-1 VSadded, respectively. The percentages of biotransformation of these substrates into methane were 85 ± 8, 85 ± 7, 88 ± 9, 85 ± 8 and 85 ± 8%, respectively. On the other hand, the first-order rate constants obtained from the experimental data were 0.24 ± 0.14, 0.23 ± 0.15, 0.27 ± 0.13, 0.31 ± 0.17 and 0.23 ± 0.13 d-1, respectively. Conclusion: The influence of inocula and experimental factors was nearly insignificant with respect to the extents of the anaerobic biodegradation, while the rates differed significantly according to the experimental approaches. © 2011 Society of Chemical Industry.

Hermann B.G.,University Utrecht | Debeer L.,Organic Waste Systems NV | De Wilde B.,Organic Waste Systems NV | Blok K.,University Utrecht | Patel M.K.,University Utrecht
Polymer Degradation and Stability | Year: 2011

Many life cycle assessments of bio-based and biodegradable materials neglect the post-consumer waste treatment phase because of a lack of consistent data, even though this stage of the life cycle may strongly influence the conclusions. The aim of this paper is to approximate carbon and energy footprints of the waste treatment phase and to find out what the best waste treatment option for biodegradable materials is by modelling home and industrial composting, anaerobic digestion and incineration. We have compiled data-sets for the following biodegradable materials: paper, cellulose, starch, polylactic acid (PLA), starch/polycaprolactone (MaterBi), polybutyrate-adipate- terephthalate (PBAT, Ecoflex) and polyhydroxyalkanoates (PHA) on the basis of an extensive literature search, experiments and analogies with materials for which significant experience has been made. During biological waste treatment, the materials are metabolised so a part of their embodied carbon is emitted into air and the remainder is stored as compost or digestate. The compost or digestate can replace soil conditioners supporting humus formation, which is a benefit that cannot be achieved artificially. Experimental data on biodegradable materials shows a range across the amount of carbon stored of these materials, and more trials will be required in the future to reduce these uncertainties. Experimental data has also shown that home and industrial composting differ in their emissions of nitrous oxide and methane, but it should be noted that data availability on home composting is limited. The results show that anaerobic digestion has the lowest footprint for the current level of technology, but incineration may become better in the future if energy efficiency in waste incineration plants improves significantly. Home composting is roughly equal to incineration with energy recovery in terms of carbon and energy footprint when carbon credits are considered. The same applies to industrial composting if carbon credits are assigned for compost to replace straw. Carbon credits can therefore considerably affect the results, but there are significant uncertainties in how they are calculated. Incineration may become better than home composting in the future if the average energy efficiency in waste incineration plants improves significantly. However, biological waste treatment options should be chosen when soil carbon is a limiting factor. © 2011 Published by Elsevier Ltd.

De Baere L.,Organic Waste Systems NV | Mattheeuws B.,Organic Waste Systems NV
Eau, l'INDUSTRIE, les Nuisances | Year: 2010

«Department... Methanization»: This article inaugurates a series of presentations about methanization They underscore some particulariy interesting, innovating or original aspects ...or deal simply with themes and technologies directly connected to it. Essentially, they are based on industrial operations and concerns encountered in the field. We begin this series with an article about continuous fermentation "on the farm" under "dry fermentation" conditions. The various methanization categories are classified according to their dry matter (DM) content. This governs the technology of the digester used and the implementation of the digestion process which can be continuous or discontinuous. The methanization of «effluents», whether they contain suspended matter or not, takes place for up to 5 to 8% of DM in the digester. Beyond this, the process concerns the digestion of solids (waste, energy-producing crops, etc.). For up to 20% of Dry Matter, the process concerns «wet fermenting» with an optimum of between 10 and 15% DM and between 20 and 45% DM in the digester, we changed to «dry» fermenting with an optimum of around 30 to 35% DM. Digesters on the farm are essentially continuous wet fermenters or discontinuous dry fermenters. In the following, we refer to an industrial example of continuous dry fermenting for an energy-producing crop. The technology derives directly from that of the methanization of the organic fraction of household refuse (or bio-waste). The announced performance is noteworthy.

Lopez M.J.,University of Almeria | Suarez-Estrella F.,University of Almeria | Vargas-Garcia M.C.,University of Almeria | Lopez-Gonzalez J.A.,University of Almeria | And 4 more authors.
Biomass and Bioenergy | Year: 2013

Four lignocellulosic wastes (wood fiber, grass, corn stover and wheat straw) were treated with the ligninolytic fungus Phanerochaete flavido-alba to improve their anaerobic digestion. After 21 days solid substrate culture, lignin content was depleted in all materials by fungus in a range between 5 and 20%, but cellulose and hemicellulose were also biodegraded. Anaerobic biodegradability of corn stover, grass and wood fiber increased as a consequence of fungal treatment. Biogas production was enhanced only in wood fiber. Fungal delignified wood fiber produced 124 NL biogas kg-1 dry wood fiber with a 64% methane, after 21 days anaerobic digestion; while non-inoculated controls did not produce any biogas. Pre-digestion of agricultural wastes (corn stover, grass and wheat straw) before biodelignification treatment failed to improve subsequent biogas production. © 2013 Elsevier Ltd.

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