- Samples are degraded in active compost through which air is passed under controlled conditions.
The evolved ammonia and water are removed and the evolved carbon dioxide is absorbed by soda lime (sodium hydroxide).
Evolved carbon dioxide is calculated from the weight increase of the soda lime.
- Reaction columns can be controlled at a user-specified temperature.
If following ISO14855-2, the temperature is typically held at 58 °C.
- Samples are weighed periodically during the test period.
- According to ISO14855-2, evaluation of biodegradability requires three tests:
a) compost only (blank), b) compost mixed with a standard (cellulose) and c) compost mixed with the sample of interest.
As shown in Fig. 2, the results obtained by MODA are recognized as reproducible.
Fig.1 Principle of MODA-6
Fig.2 Experiments on aerobic biodegradation of PLA by MODA
- Determination of test material biodegradability by evolved biogas
- Wet methane fermentation in slurry phase (TS* < 15%)
*TS = total solids (%) = 100 – W (W = % moisture content)
- Wet methane fermentation in slurryphase（TS<15%）
- Volume of test mixture from 1.0 – 1.5 L
- Number of samples: 6 (2x test material, 2x reference and 2x blank samples compared simultaneously)
- Fermentation at thermophilic temperature: 55 °C
- Fermentation at atmospheric pressure
- Measurement of evolved biogas by a syringe or gas burette
- Amount of test materials: 10 g
Fig. 3 Principle of MODA-B
Fig. 4 Anaerobic biodegradation of PLA at 55℃
In this century, people are trying to establish an environmentally-friendly society to balance human society with the global environment. Particularly, microplastics are becoming one of the major issues for the global environment.
Chemical engineers are developing plastic materials which can be biodegraded in various conditions such as compost, soil, aqueous or anaerobic digestion in activated digested slurries. However, the plastics should not simply ‘disintegrate’ into small and fine fragments (oxo-degradation) but should be ‘completely biodegradable’ to carbon dioxide under controlled anaerobic condition.
To avoid misuse or misunderstanding of the term ‘biodegradability’, unified test procedures according to international standards have been established. For example, according to the standards laid out in ISO14855-2:2007, PLA is proven as a biodegradable plastic that is biodegraded by more than 90% after 45 days at 58 °C in compost (Fig. 2). Hence, PLA has became one of the most recognized biodegradable plastics in the world.
ISO14855-2 and MODA apparatus
In the testing of ‘biodegradability’, ISO14855-1:2005 (ASTM5338-11 , EN14046:2003 ), namely the aerobic biodegradation of plastics in compost, was an established procedure. However, the procedure had difficulty in reproducing over 70% cellulose biodegradation in Japan. In order to investigate and identify a solution, a national project started in 2000 to develop a suitable apparatus and test procedure under the leadership of JBPA (Japan BioPlastic Association) and with the cooperation of AIST (National Institute of Advanced Industrial Science and Technology) plus several universities.
Microbial activity in matured compost was found to depend on the water content of that compost. Since European mature compost only has a small volatile content, it can yield sufficient microbial activity for biodegradation testing with relatively little water. On the other hand, Asian mature compost, including Japanese, has much higher volatile content and thus, microbial activation by water is over a relatively short time and soon the microbial activation is significantly decreased.
Adding sea sand or vermiculite to mature compost dilutes the volatile material content and keeps the water holding capacity at an appropriate level. Test results became almost the same as those of European countries. In addition, by using our apparatus called MODA (Microbial Oxidative Degradation Analyzer) we succeeded in decreasing the loading of compost to 1/10th of the quantity of test material required by ISO14855-1 by introducing a precise ‘Gravimetric Procedure’ to measure the amount of CO2 generated.
Based on the original MODA apparatus, the MODA-4 and MODA-6 were developed and are now available. Please see ‘Products & Services’ for features and specifications.
As well as the importance of ISO standards and apparatuses, we became aware of the importance of methods used to prepare and adjust compost. Since biodegradation is done by microbial life forms, the methods for preparation and adjustment of compost have a substantial impact on the results of testing.
Insufficiently matured compost easily generates ammonia because it has a high volatile content. However, over-matured compost (in which most microbials are dormant) has a low level of activation. The consequence can be that biodegradation of the reference material (cellulose) does not reach 70% even after 45 days of testing. If water content of the compost is too low, the same result is observed as for over-matured compost. Conversely, if water content is too high, anaerobic fermentation occurs and the test becomes invalid. Additionally, the preincubation process of each compost may differ from country to country. Attempting various alternatives using cellulose as a reference material is useful in identifying the best preincubation process. In addition to aerobic testing, we developed an apparatus called MODA-B to carry out anaerobic testing under conditions according to ISO13975. Please see ‘Products & Services’ for features and specifications.
Narayan. R; Misleading Claims and Misuse of Standards continue, bioplastics MAGAZINE, issue 02/2010, page 38.
ISO14855-2:2007 Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions – Method by analysis of evolved carbon dioxide – Part2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test
ISO14855-1:2005 Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions – Method by analysis of evolved carbon dioxide – Part1: General method
ASTM5338-11 Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions. Incorporating Thermophilic Temperatures
 EN14046:2003 Packaging. Evaluation of the ultimate aerobic biodegradability and disintegration of packaging materials under controlled composting conditions. Method by analysis of released carbon dioxide.
ISO13975 Determination of the ultimate anaerobic biodegradation of plastic materials in controlled slurry digestion systems – Method by measurement of biogas production
Papers related to MODA
- Biodegradability Evaluation of Polymers by ISO 14855-2, M. Funabashi, F. Ninomiya, M. Kunioka, International Journal of Molecular Science, 2009, 10(8), 3635–3654. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2812819/)
- The effect of Thai compost on biodegradability of polylactic acid baced on ISO 14855-2 method, W. Timbuntam, S. Pongsomnam, W. Vanichsriratana, P. Sukyai, Advanced Materials Research, 2011, Volumes 415-417, 2184-2190. (https://www.scientific.net/AMR.415-417.2184)
- Measure Biodegradability of Plastics More Accurately, F. Castellani, A. Esposito, V. Stanzione, R. Altieri, Advances in Materials Science and Engineering, 2016, Article ID 6909283, 7 pages. (https://www.hindawi.com/journals/amse/2016/6909283/)
- Carbon transformations by attached bacterial populations in granitic groundwater from deep crystalline bed-rock of the Stripa research mine, S. Ekendahl, K. Pedersen, Microbiology, 1994, 140 ( Pt 7), 1565-1573. (https://www.ncbi.nlm.nih.gov/pubmed/8075798)
- Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge, H. Yagi, F. Ninomiya, M. Funabashi, M. Kunioka, International Journal of Molecular Science, 2009, 10(9), 3824–3835. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769157/)
- BIOPLASTICS: TECHNOLOGY PRINCIPLES AND EXEMPLARS, R. Narayan, Society of Plastics Engineers Global Plastics Environmental Conference, 2007.
- Biodegradability…Sorting through Facts and Claims, R. Narayan, bioplastics MAGAZINE, 2009, [01/09], Vol.4, 28-31. (https://www.bioplasticsmagazine.com/bioplasticsmagazine-wAssets/docs/article/0901_p29_bioplasticsMAGAZINE.pdf)
- Anaerobic Biodegradation of Surfactants – Scientific Review, J. L. Berna, G. Cassani, C.-D. Hager, N. Rehman, I. López, D. Schowanek, J. Steber, K. Taeger, T. Wind, Tenside Surfactants Detergents, 2009, Vol. 46, No. 1, 53-62. (https://www.hanserelibrary.com/doi/abs/10.3139/113.100351)
- Misleading Claims and Misuse of Standards Continues to Proliferate in the Nascent BioPlastics Industry Space, R. Narayan, bioplastics MAGAZINE, 2002, [01/10], Vol.5, 38-41. (https://www.bioplasticsmagazine.com/bioplasticsmagazinewAssets/docs/article/1001_p38_bioplasticsMAGAZINE.pdf)
- ACCURATIVE AND EASY EVALUATION OF AEROBIC MICROBIAL-DEGRADABILITY OF BIODEGRADABLE PLASTICS UNDER CONTROLLED SOIL, S. Uematsu, A. Murakami, K. Hiyoshi, Y. Tsukamoto, H. Saida, M. Tsuji, A. Hoshino, Polymer Preprints, 2002, 43(2), 930-931. (https://www.saidagroup.jp/fds_en/wp/wp-content/uploads/2018/10/acs.pdf)
Flow-type Microwave Reactor
Our flow-type microwave reactor is a system composed of a microwave unit a pump unit. In this reactor, SAIDA’s microwave technology can achieve rapid and uniform heating of a flow channel. Therefore, this system not only provides advantages over conventionally-heated flow reactors, but also allows a method to scale-up reactions normally conducted in a batch-type microwave reactor. Furthermore, the system allows safe operation at extreme conditions (Max. temperature: 230 °C; Max. pressure: 2.5 MPa), because the reaction field is more compact than a batch-type reactor and internal pressure/temperature is continuously monitored.
- single-mode cavity
- microwave frequency control
- safety system (monitoring: temperature, pressure, and microwave power)
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