Modelled on Nature – Biological Processes in Waste Management

Abstract

Biological degradation and transformation of organic substances under aerobic or anaerobic conditions are key processes within the natural metabolism of an equilibrated circulation system in order to handle the accumulating biomass. These fundamental processes are the basis for management strategies focusing on the biological treatment of organic waste materials. They are subjected to the biochemical metabolism using the capability of microbial populations to degrade, transform and stabilise organic matter. Stabilisation comprises biological as well as abiotic chemical and physical processes and their interaction. Avoiding greenhouse gases and shortening the after care period stabilisation is the key target for safe waste disposal in landfills. Biogenic waste materials are a source of secondary products: biogas obtained by anaerobic digestion and composts produced under aerobic conditions. For composts stabilisation is a relevant process to achieve plant compatibility and persistent organic substances for soil amelioration. Biological processes additionally contribute to landfill remediation, e.g. by methane oxidation. Nevertheless, biological degradation of waste materials is ambivalent and can lead to harmful effects if microbial activities take place under uncontrolled conditions in imbalanced systems. Abandoned landfills from the past demonstrate this fact. Anthropogenic organic wastes differ from “natural” organic waste by their amount, their heterogeneity and the content of xenobiotics. Therefore it is necessary to support and optimise biological degradation of waste organic matter by adequate process operation and technical devices. The equilibrium of necessary mineralisation and accessible humification is a topic of high interest in the context of carbon fixation. “Optimisation” is no aspect in the context with natural degradation processes. Additionally they are not harmless a priori. They take place under the current conditions, but it can be assumed that an equilibrium is reached over longer periods of time. Changes of environmental conditions by anthropogenic activities can accelerate biological degradation. Peat bogs that were drained and amended with carbonates lose organic matter due to mineralisation (Küster, 1990). The pH value, water and air supply and temperature mainly influence the transformation rate. This fact indicates that biodegradability is not only an inherent property that depends on chemical and physical features of the material. The behaviour of biodegradable substances is affected by the interaction of both material characteristics and environmental conditions.