The standard "EN ISO 14855 Determination of ultimate aerobic biodegradability of plastic materials under controlled composting conditions - Method for analysis of evolved carbon dioxide", which is a European standard and subsequently published by the International Organization for Standardization (ISO), consists of the following subsections published under the same title:
The test material is exposed to an inoculum derived from compost. Composting occurs in an environment where temperature, ventilation, and humidity are closely monitored and controlled. The test method is designed to determine the percentage and rate of conversion of carbon in the test material to released carbon dioxide.
This standard describes a method that uses a mineral bed (vermiculite) inoculated with thermophilic microorganisms derived from compost with a specific activation phase, rather than mature compost. This variant is designed to obtain the percentage and conversion rate of carbon in the test material to carbon dioxide.
The conditions described in this standard may not always correspond to the optimum conditions for the maximum degree of biodegradation to occur.
This test method essentially determines the ultimate biodegradability and degree of degradation of the test material under conditions simulating intensive aerobic composting. The inoculum used consists of stabilized, mature compost obtained by composting the organic fraction of solid municipal waste, if possible.
The test material is mixed with inoculum and placed in a static composting container where it is intensively composted for a test period not exceeding 6 months under optimum oxygen, temperature and humidity conditions.
During aerobic biodegradation of test material, carbon dioxide, water, mineral salts, and new microbial cellular components (biomass) are the final biodegradation products. The carbon dioxide produced is monitored continuously in the test and empty vessels or measured at regular intervals to determine cumulative carbon dioxide production. The percentage biodegradation is given as the ratio of the carbon dioxide produced by the test material to the maximum theoretical amount of carbon dioxide that could be produced from the test material. The maximum theoretical amount of carbon dioxide produced is calculated from the measured total organic carbon content. The percentage biodegradation does not include the amount of carbon converted to new cellular biomass that is not metabolized to carbon dioxide during the test period.
In addition, the degree of decomposition of the test material is determined at the end of the test, and the mass loss of the test material can also be determined. Instead of mature compost, vermiculite,
Because the vermiculite bed is inorganic, it significantly reduces the priming effect, increasing the reliability of the method. Another advantage of using vermiculite is that, due to its low microbial activity, very little carbon dioxide is released in empty containers (almost zero). This allows for precise assessment of low levels of decomposition activity.
The mineralization rates obtained with activated vermiculite are the same or very similar to those obtained with mature compost, both in terms of the final level of decomposition and the rate of decomposition.
This method is applicable to the following materials:
If the test material inhibits the microorganisms in the inoculum, another type of mature compost or pre-exposure compost may be used.
This method is principally designed to achieve the optimal biodegradation rate of plastic material in mature compost by controlling the humidity, aeration rate, and temperature in the composting bin. It also aims to determine the ultimate biodegradability of the test material using a small-scale reactor.
The rate of decomposition is measured periodically by determining the mass of carbon dioxide released using an absorption column filled with soda lime and soda talc on an electronic balance.
The test material is mixed with an inoculum derived from mature compost and an inert material such as sea sand. The sea sand plays an active role by acting as a moisture and microorganism-retaining medium. Examples of suitable test arrangements are provided in Annexes A and B.
The amount of carbon dioxide released is measured at intervals on an electronic balance, and the carbon dioxide content is determined by the following method. The derivation of the formula used to calculate the degree of biodegradation from the amount of carbon dioxide released is included in Appendix C. In this method, the degree of biodegradation, expressed as a percentage, is calculated by comparing the amount of carbon dioxide released with the theoretical amount.
The test is terminated when the plateau stage of biodegradation is reached. The standard time for termination is 45 days, but testing can be continued for up to six months.
In short, ISO 14855 standards are critical for assessing the biodegradability of plastics under controlled composting conditions. In particular, they play a key role in environmental sustainability by assessing how bioplastics break down in industrial composting systems.
This standard is very important for the following reasons:
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