Testing Measure
Testing Measure Biodegradability of Plastics More Accurately By Yoshi Ohno Engineering Specialist Saida FDS Inc. Shizuoka-Ken, JAPAN Shogo Uematsu former professor University of Shizuoka Background In this century, people are starting to try to establish an environmentallyfriendly society to balance human society and the global environment. Packaging materials, especially disposable packages, are becoming one of the major reasons behind a negative impact on the global environment. Chemical engineers are trying to develop plastic materials which can be biodegraded under various conditions such as compost, soil, aqueous or anaerobic digestion under activated sludge condition. However, the plastics should not simply ‘disintegrate’ into small and fine fragments (oxo-degradation) but should be ‘completely biodegradable’ to carbon dioxide and water under aerobic conditions, and to methane and carbon dioxide under controlled and captured anaerobic condition [1] ‘Biodegradability’ as an International Standard To avoid misuse or misunderstanding of the term ‘Biodegradability’, unified test procedures according to international standards have been established.. For example, when applying the test procedure in ISO14855-2:2007 [2], PLA is proven as a biodegradable plastic that is biodegraded by more than 90% after 45 days at 58°C under composting conditions (Fig.1). In this way PLA became one of the most recognized biodegradable plastics in the world. ISO14855-2 and MODA apparatus In this ‘ biodegradable ’ testing field, ISO14855-1:2005 [3] (ASTM5338-11 [4], EN14046:2003 [5]) was one of the well understood procedures, namely the aerobic biodegradable test under compost condition, but the procedure had difficulty in reproducing over 70% biodegradation of cellulose in Japan. Biodegradation (%) Fig1.Effect of repetitive experiments on aerobic biodegradation of PLA by MODA (ISO 14855-2) PLA-1, -2 Addition of urea 100 80 60 40 20 100 0 80 60 40 cellulose-1, -2 Re-addition of PLA 20 0 0 20 40 60 80 100 120 Biodegradation (%) To make the reason clear and to identify a solution, a national project started about 10 years ago to develop apparatus and a 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. As a result of various tests carried out, it was seen that microbial activity under matured compost conditions depends on the water content of the compost. It was discovered that it was very difficult to maintain an appropriate water content level for a long period. Because European matured composts have only a small volatile content, it can obtain sufficient microbial activity for biodegradation testing with relatively little water On the other hand, Asian matured composts, including Japanese, have a much higher volatile content and thus, microbial activation by water is over a relatively short time and soon the microbial activation is significantly reduced. Adding sea sand or vermiculite to mature compost dilutes the volatile material content and keeps the water holding capacity at an appropriate level. Test duration (day) 26 bioplastics MAGAZINE [04/11] Vol. 6
Testing Test results became almost the same as the test results seen in European countries. In addition, by designing the apparatus called MODA (Microbial Oxidative Degradation Analyzer) we could succeeded in reducing the amount of compost to 1/10 of the quantity of test material specified in ISO14855-1 by introducing a precise ‘Gravimetric Procedure’ to measure the amount of CO 2 generated. Based on the original MODA apparatus, Saida FDS developed the MODA-6 apparatus for which the company introduced an environmental chamber holding six reaction units in it keep temperature conditions constant and maintain the same appropriate water content. Fig2. MODA-6 apparatus This MODA apparatus was originally designed to carry out testing under compost conditions, but is also considered applicable to soil condition, Saida have started tests using the MODA apparatus for biodegradability testing under soil conditions, that is standardized as ISO17556. To make test result more reliable and accurate Biodegradability testing usually needs to take place over a period longer than two months but if test results are at not at a satisfactory level, all the efforts spent for the time became to be useless. In addition to ISO standards and apparatus, SAIDA came to understand the importance of preparation and adjustment of the compost, because biodegradation is done by microbial life forms. Depending on how well preparation and adjustment of compost are done has a substantial impact on the results of testing. Insufficiently matured compost easily generates ammonia because it has a high volatile content. On the contrary, over-matured compost in which most of microbials are dormant has a low level of activation and sometimes causes the situation that the reference material cellulose cannot reach at 70% of biodegradation even though it takes 45 days for testing. In dry conditions of composting the water content is too low, and causes same result as over-matured compost. And if the water contents in compost is too high, it becomes an anaerobic fermentation and the test falls into the area of invalid result. As explained above, a preincubation process for compost is very important to obtain appropriate test results, and is well understood. This preincubation process may differ from compost to compost in each country. To identify the best preincubation process, trying various alternatives using cellolose as a reference material helps a lot. Recently Saida established a laboratory and started biodegradation research and testing by having the support of Dr.Uematsu, former professor of University of Shizuoka. In addition to aerobic testing, Saida developed an apparatus called MODA-B to carry out testing under anaerobic conditions (standardization is under way as ISO/DIS13975). • www.saidagroup.jp [1] Narayan, R: Misleading Claims and Misuse of Standards continue, ‘bioplastics MAGAZINE, issue 02/2010, page 38. [2] ISO14855-2:2007 Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions -- Method by analysis of evolved carbon dioxide -- Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test [3] ISO14855-1:2005 Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions -- Method by analysis of evolved carbon dioxide -- Part 1: General method [4] ASTM5338-11 Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions. Incorporating Thermophilic Temperatures [5] 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 bioplastics MAGAZINE [04/11] Vol. 6 27
