ASTM D5526-94

Decomposition of a plastic within a landfill involves biological processes that will affect the decomposition of other materials enclosed by, or in close proximity to, the plastic. Rapid degradation of the plastic may 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 biodegradation during the active life of the landfill. This procedure has been developed to permit determination of the anaerobic biodegradability of plastic products when placed in biologically active environments simulating landfill conditions.

The decomposition of plastic materials in a landfill is of limited importance, as few landfills are operated so as to be biologically active. However, as degradation occurs inevitably 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 may occur in a landfill. The mixtures remaining after completion of the test method, containing fully or partially degraded plastic materials or extracts, can be submitted subsequently to ecotoxicity testing in order to assess the environmental hazards posed by the breakdown of plastics to varying degrees in landfills. This test method has been designed to assess biodegradation under optimum and less-than-optimum conditions.

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 environment 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 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.

1.1 This test method covers determination of the degree and rate of anaerobic biodegradation of plastic materials in an accelerated-landfill test environment. This test method is also designed to produce mixtures of household waste and plastic materials after different degrees of decomposition under conditions that resemble landfill conditions. The test materials are mixed with pretreated household waste and exposed to a methanogenic inoculum derived from anaerobic digesters operating only on pretreated household waste. The anaerobic decomposition occurs under dry (more than 30 % total solids) and static nonmixed conditions. The mixtures obtained after this test method can be used to assess the environmental and health risks of plastic materials that are degraded in a landfill.

1.2 This test method is designed to yield a percentage of conversion of carbon in the sample to carbon in the gaseous form under conditions that resemble landfill conditions. This test method may not simulate all conditions found in landfills, especially biologically inactive landfills. This test method more closely resembles those types of landfills in which the gas generated is recovered or even actively promoted, or both, for example, by inoculation (codeposition of anaerobic sewage sludge and anaerobic leachate recirculation), moisture control in the landfill (leachate recirculation), and temperature control (short-term injection of oxygen and heating of recirculated leachate) (1-7).

1.3 This test method is designed to produce partially degraded mixtures of municipal solid waste and plastics that can be used to assess the ecotoxicological risks associated with the anaerobic degradation of plastics after various stages of anaerobic biodegradation in a landfill.

1.4 The values stated in SI units are to be regarded as the standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazards statements are given in Section 8.

Note 1—There is no similar or equivalent ISO standard.