Assessing anaerobic biodegradability of polymeric materials under acidogenic or methanogenic conditions

Abstract

The anaerobic degradation of polymeric materials was studied in batch tests by determination of the conversion yields to volatile fatty acids (acidogenesis) or to methane (methanogenesis). By both methods, filter paper, polyhydroxybutyrate (PHB), and two starch‐containing plastic materials (low and high starch contents) were examined with glucose and polyethylene as positive and negative control, respectively. Conversion yields were expressed in terms of Theoretical Oxygen Demand (ThOD). Methanogenesis and acidogenesis are basically analogous with respect to the final conversion yield. PHB and filter paper show a high conversion yield, comparable to glucose. The material with low amount of starch additive presents very low conversion yields, whereas the starch‐based material is significantly degraded, even if in percentages not higher than starch content. Acidogenic tests are always quicker than methanogenic tests. The rate determining step is generally the hydrolysis of the particulate substrate in the case of acidogenesis and the methane formation in case of methanogenesis. Moreover, acidogenesis appears less sensitive to inhibition in the presence of sulphate. For these reasons, monitoring VFA production after chemical inhibition of methanogenesis can be a good alternative to methane monitoring for assessing anaerobic biodegradability of polymeric materials.