Composting at laboratory scale

The composting test method based on activated vermicuUte was proposed as a comprehensive system for the assessment of the environmental impact of compostable polymers [1, 2]. Vermicnlite, a clay mineral, can be activated (by an inoculation with an appropriate microbial population and fermentation) and used as a sohd matrix in place of mature compost in the controlled composting test. The formula of vermicnlite is (MgJ e,Al)3(Al,Si)40io(OH)2.4H20. The results obtained with two materials (cellulose and a starch-based blend) indicated that activated vermicnlite affected neither the biodegradation rate nor the final biodegradation level. 

Different veimicuhte media were studied in order to determine the parameters of an inert solid medium which could simulate the degradahon of a polymer in compost [3]. Five different vermiculite media have been tested according to type of activahon and the amount of inoculum used. The mineralizahon curves obtained for simulation tests have been compared with the mineralization curve of starch biodegradahon in compost. 

The respirometric method meastues either CO2 produced or CO2 constuned or both of them in an enclosed system with proper maintenance or regulation of air or oxygen supply. This technique is especially suitable for confirmation on the extent of mineralization It can be used for measuring degradation of soluble powder from fragile pofymeric materials. This method is easily adapted to a whole range of envirorunental conditions and/or specified or mixed culture microorganisms. 

The air with its CO2 is poured into dehumidifying traps to remove the moisture from the stream in air for an accurate carbon weight balance and then poured into an absorption column of carbon dioxide and an absorption colunrn of water. In these two columns with soda lime (NaOH inunobilized to slaked lime) and soda talc (NaOH inunobilized to talc), the produced CO2 is absorbed by the reactions indicated in Eq. (1)  

The produced H2O is simultaneously trapped in these two columns. The weight of these two columns is increased the same as the weight of the produced CO2, thus the produced CO2 is easily obtained by a gravimetric method 

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