Altogether 33 preservative substances were tested at different concentrations in a pile-simulator containing 500 g of fresh bagasse. As an indicator for thetoxicity against the microflora the temperature was measured; a constancy of the initial temperature indicates no activity, because no energy is released due to consumption of material, whilst a modification of the temperature curve typical for fresh bagasse indicates beginning effectivity of the preservative (Fig. 2). Most effective were organic sulfuric compounds (0.2%, 0/1%), boric acid was not toxic enough and propionic acid showed a beginning effectivity only at 1,6%.