BS ISO 14853:2016 pdf download

BS ISO 14853:2016 pdf download.Plastics — Determination of the ultimate anaerobic biodegradation of plastic materials in an aqueous system
4 Principle
The biodegradability of a plastic material is determined using anaerobic conditions in an aqueous system. Test material with a concentration of 20 mg/l to 200 mg/l organic carbon (OC) is incubated at (35 ± 2) °C in sealed vessels together with digested sludge for a period normally not exceeding 90 d. Before use, the digested sludge is washed so that it contains very low amounts of inorganic carbon (IC) and diluted to 1 g/l to 3 g/l total solids concentration. The increase in headspace pressure or the volumetric increase (depending on the method used for measuring biogas evolution) in the test vessels resulting from the production of carbon dioxide (CO 2 ) and methane (CH 4 ) is measured. A considerable amount of CO 2 will be dissolved in water or transformed to bicarbonate or carbonate under the conditions of the test. This inorganic carbon (IC) is measured at the end of the test. The amount of microbiologically produced biogas carbon is calculated from the net biogas production and the net IC formation in excess of blank values. The percentage biodegradation is calculated from the total amount of carbon transformed to biogas and IC and the measured or calculated amount of carbon added as test material. The course of biodegradation can be followed by making intermediate measurements of biogas production. As additional information, the primary biodegradability can be determined by specific analyses at the beginning and end of the test. This test method is designed to determine the biodegradability of plastic materials under anaerobic conditions. Optionally, the assessment of the recovery rate may also be of interest (see Annex G).
5.6 Test material.
The test material is usually added directly as solid to give a concentration of 20 mg/l to 200 mg/l organic carbon. The test material (plastic) should be used in powdered form, if possible. The test material should preferably be used in powder form, but it may also be introduced as films, pieces, fragments or shaped articles. The form and shape of the test material may influence its biodegradability. Similar shapes should preferably be used if different kinds of plastic material are to be compared. If the test material is used in the form of a powder, particles of known, narrow size distribution should be used. A particle-size distribution with the maximum at 250 µm diameter is recommended. Also, the size of the test equipment used may depend on the form of the test material. The biodegradability of plastic materials which are not inhibitory to microorganisms can be determined using concentrations higher than 200 mg/l organic carbon. In this case, ensure that the buffer capacity and mineral-salt content of the medium are sufficient.