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The method assesses the extent of breakdown of test materials in a laboratory setting, replicating the conditions of a vigorous aerobic composting process. The testing involves a synthetic solid waste matrix infused with mature compost sourced from either a municipal or industrial composting facility. Plastic test pieces are then composted within this formulated solid matrix for normally 45 to 90 days at 58 °C. Following a composting cycle, the degree of breakdown is determined by sifting the resulting matrix through a 2 mm sieve to retrieve any remaining undecomposed residues. The reduction in the test sample's mass is regarded as disintegrated material, serving as the basis for calculating the extent of disintegration.
▶ Materials that can be tested:
➢ Plastics and many other types of materials;
▶ Synthetic solid waste: 55% of water content and C/N of 20:1 to 40:1. Composition by dry mass:
➢ Sawdust (40%);
➢ Rabbit-feed (30%);
➢ Ripe compost (up to 4 months old, 10%);
➢ Corn starch (10%);
➢ Saccharose (5%);
➢ Cornseed oil (4%);
➢ Urea (1%) .
▶ Composting reactor: 30 cm × 20 cm × 10 cm (l, w, h) with 5 mm holes on the two 20 cm wide sides;
▶ Number of reactors: 3 for each test substance;
▶ Test substance size: 25 x 25 x thickness (thickness < 5 mm), or 15 x 15 x thickness (5mm < thickness < 15 mm);
▶ Test substance dosage: 5-20 g per 1 kg of wet synthetic waste;
▶ Testing conditions:
➢ Temperature: 58 °C ± 2 °C;
➢ Frequent mixing and watering;
▶ Duration: 45-90 days.
▶ Measurement: sieve the mixtures after composting with 10 mm, 5 mm, and 2 mm sieves to collect the remaining test substance. Wash and dry the test substance and determine its weight;
▶ Test validity criteria:
➢ Decrease in volatile-solids content is over 30%;
➢ The degrees of disintegration for the three replicates shall not differ by more than 20 %;
▶ When ISO 20200 is used as part of ASTM D6400, a plastic product is considered to have demonstrated satisfactory disintegration if after twelve weeks (84 days) in a controlled composting test, no more than 10 % of its original dry weight remains after sieving on a 2.0-mm sieve.
To learn more about different types of biodegradation tests, their applicability, biodegradation mechanisms, and many other information such as case studies, publications, and blogs, please check our Aropha Resource Center