Effects of Temperature on Anaerobic Lignin Degradation in Bioreactor Landfills

Abstract

Bioreactor landfills have become a feasible alternative to the typical "dry tomb" landfill. By recirculating leachate and/or adding additional liquid wastes, bioreactor landfills operate to rapidly degrade and transform organic wastes. The reactions within a bioreactor landfill create elevated temperatures. The intent of this study was to determine the effect of elevated temperature on the degradation of lignocellulose compounds. In order to observe the effects of temperature on lignin, small bioreactors were created in the laboratory. Several experiments were performed by the authors. Solubility of lignin based on temperature and time of thermal exposure were conducted. In addition, degradation studies were conducted based on biological treatment of lignin as well as a combination of biological and thermal treatment. Samples were collected at specified intervals to determine the amount of water soluble lignin (WSL), volatile fatty acids (VFAs), lignin monomers, and/or methane present. Lignin solubility increased as temperature rose in the thermal solubility experiments. The rate of solubility increased 15 times for office paper and 1.5 times for cardboard in the biological experiments when compared to the thermal treatment. The thermal and biological study indicates that as lignin is solubilized, it breaks down into lignin monomers, which can be converted easily by anaerobic bacteria into VFAs and subsequently, methane. These experiments indicate that temperature is crucial to the degradation of lignin compounds in a bioreactor landfill.