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 o btained with two materials (cellulose and a starch-based blend) indicate th at activated vermiculite affects neither the biodegradation rate nor the fi nal biodegradation level. On the other hand, possible metabolic intermediat es and polymeric residues left after biodegradation can be recovered more e asily from activated vermiculite than from mature compost, a very complex o rganic 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 o riginally in the test material. This work was partly financed by the Europe an Commission (DGXII) with the SMT "Labelling biodegradable products" proje ct SMT4-CT97-2187. (C) 1999 Elsevier Science Ltd. All rights reserved.