Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated Bioreactor Landfill Conditions

Importancia y uso:

5.1 Decomposition of a plastic within a landfill involves processes in aerobic and anaerobic environmental conditions that can affect the decomposition of other materials enclosed by or in close proximity to the plastic. The rate of change from aerobic to anaerobic conditions is probably a characteristic of the particular landfill site, its garbage and the filling technique and is therefore difficult to assess with any degree of accuracy. Different sources indicate days to months (Refs (8) and (9)) for this change with the spread dependent on the perspective of what is aerobic or anaerobic and how fast the environment changes, 30 days is chosen in this method as a compromise time period. (Note, even very low levels of oxygen, far below normal atmospheric concentration can promote oxidative degradation). Obviously, there will be pockets of protected (in bags, cans, etc.) aerobic activity enclosed in any landfill. There is currently no evidence or data to support claims that rapid degradation of the plastic (when compared to conventional non-degradable plastic) can increase the economic feasibility of landfill-gas recovery, minimize the duration of after-care of the landfill, and make possible the recovery of the volume reduction of the waste due to degradation and biodegradation during the active life of the landfill. Additionally, it is possible that the rapid degradation and biodegradation of plastics can create hazardous conditions in landfills, such as the shifting of cells and overall stability. This standard method has been developed to permit determination of the aerobic degradation and anaerobic biodegradation of plastic products when placed in biologically active environments simulating some landfill conditions.

5.2 The decomposition of plastic materials in a landfill is of importance, as most landfills are biologically active and are an increasingly significant source of renewable energy. As degradation occurs in a landfill, it is of immediate concern that the plastic materials do not produce toxic metabolites or end products under the various conditions that occur in a landfill. The mixtures remaining after completion of the test method, containing fully or partially degraded plastic materials or extracts can be, when appropriate, submitted subsequently to ecotoxicity testing, see Practice D5951 and Guide D6954 for details, in order to assess the environmental hazards posed by the breakdown of plastics to varying degrees in landfills, especially if leaching occurs. This test method has been designed to assess aerobic degradation and anaerobic biodegradation under optimum and less-than-optimum conditions and toxicity.

5.3 Limitations—Because a wide variation exists in the construction and operation of landfills, and because regulatory requirements for landfills vary greatly, this procedure is not intended to simulate the environments of all landfills. However, it is expected to closely resemble the environment of a biologically active landfill. More specifically, the procedure is intended to create a standard laboratory environment that permits rapid and reproducible determination of the aerobic degradability and anaerobic biodegradability under accelerated landfill conditions, while at the same time producing reproducible mixtures of fully and partially decomposed household waste with plastic materials for ecotoxicological assessment.

Subcomité:

D20.96

Volúmen:

08.03

Número ICS:

13.030.40 (Installations and equipment for waste disposal and treatment)

Palabras clave:

accelerated landfill; anaerobic biodegradation; biodegradation; aerobic degradation; dry digestion; ecotoxicity; landfill; metabolites; plastics; test method;