CHARACTERIZATION OF SPENT MUSHROOM SUBSTRATE USING THE LEACHING BEHAVIOUR TEST.

Mushroom production generates a considerable amount of spent mushroom substrate, difficult to utilize at the site of production. The high amount of organic matter and nutrients in the waste justifies its environmental use. However, waste entering the environment undergoes transformations, the direction and intensity of which depend on, among other things, environmental conditions. Extreme environmental conditions (such as very low or high pH) can significantly change the properties of introduced material and, as a result, pose a risk to the environment. The aim of this study was to determine the effect of pH value during leaching on chemical properties of the leachates obtained from the spent mushroom substrate. The leaching behaviour test was conducted taking into account the effect of pH on leaching with the initial acid/base addition (the procedure was conducted according to the PN-EN 14429 standard). The content of selected macroelements and heavy metals in the leachates was determined by inductively coupled plasma optical emission spectroscopy. The leachates were obtained at nine pH values (from 3 to 11.5, including natural pH of the material amounting to 7). The highest element content was recorded in the leachates obtained after the strongest acidification of the spent mushroom substrate. As a rule, the content of leached macroelements decreased as the pH increased. The content of leached Mn and Zn also decreased as the pH increased (contrary to the case of Cu). In the case of Fe, after the initial reduction in its content, an increase was recorded in strongly alkaline samples. Element content in acid leachates was as follows: Ca > K > P > Mg > Mn > Zn > Fe > Cu > Cr > Cd > Ni. Only traces of Pb were found in the leachates (regardless of pH) as well as traces of Ni, Cd and Cr (except the leachates with the lowest and/or highest pH). [ABSTRACT FROM AUTHOR]