Activated vermiculite, a solid bed for testing biodegradability under composting conditions

Vermiculite, a clay mineral, can be activated and used as a solid matrix in place of mature compost in the controlled composting test, a respirometric essay widely applied to assess biodegradability of plastics. The results obtained with two materials (cellulose and a starch-based blend) indicate that activated vermiculite affects neither the biodegradation rate nor the final biodegradation level. On the other hand, possible metabolic intermediates and polymeric residues left after biodegradation can be recovered more easily from activated vermiculite than from mature compost, a very complex organic matter. Therefore, at test termination it was possible to determine the carbon balance taking into account both the evolved CO2 and a polymeric residue extracted from vermiculite, totalling 101% of the carbon present originally in the test material. This work was partly financed by the European Commission (DGXII) with the SMT "Labelling biodegradable products" project SMT4-CT97-2187. (C) 1999 Elsevier Science Ltd. All rights reserved.