ANAEROBIC DIGESTION PLANT

Anaerobic Digestion Plant



Anaerobic Digestion Plant

Introduction

Investment decisions are mainly based on the capacity of the project in generating profits. The investment analysis considers and highlights the risk associated with the project which is expressed by the volatility of the NPV or the likelihood that you cannot meet the expenditures required to continue the project. This paper will focus on the Anaerobic Digestion plant that will generate bio-methane, whether this project is feasible for future benefit and what will be the benefits of implementing this project.

Discussion

Anaerobic Digestion Project

Anaerobic digestion is the process in which microorganisms materials decompose biodegradable in the absence of oxygen. This process generates various gases, among which the carbon dioxide and methane are the most abundant (depending on the material degraded). The intensity and duration of the anaerobic process varies depending on various factors, among which include the temperature and the pH of the material biodegraded. Anaerobic digestion (AD) is a multistage process that can be summarized in four stages (Karellas S., Boukis L., Kontopoulos G., 2010, 1273).

The first is due to hydrolyze, higher molecular compounds has more weight, both dissolved and non-dissolved by enzymes (e.g., proteases and amylases), in this first step, they are hydrolyzed polymers such as polysaccharides, lipids, proteins and nucleic acids , forming the corresponding oligomers and monomers (sugars, alcohols, fatty acids, glycerol, polypeptides, amino acids, alkali bases, and aromatics).

The second stage is carried out Acidogenic bacteria that convert the oligomers and monomers to volatile fatty acids (acetic, propionic acid, butyric and valeric acid mainly)

Acetogenic bacteria in the third stage transform volatile fatty acids (VFA) in acetic acid, to turn acetoclastic bacteria methanogenic bacteria,

In the last stage, transformed to methane (CH 4) and carbon dioxide (CO 2), in this fourth stage, it also involved hydrogenotrophic bacteria that maintain the balance of hydrogen (H 2) in the middle, using it to reduce the CO 2 to CH 4 (Bywater A., 2011, pp. 5).

The Phases of Anaerobic Digestion

Anaerobic digestion is characterized by the existence of several distinct consecutive phases in the process of degradation of the substrate (generic term for generally the food of microorganisms), speaking 5 large populations of microorganisms. These populations are characterized by being composed of different growth rates and different sensitivities to each intermediate compound as an inhibitor (e.g. H2, acetic acid or ammonia produced from the amino acid acidogenesis).

This implies that each stage will present different reaction rates as substrate composition and stable development of the overall process will require a balance to avoid the accumulation of inhibitory intermediates or accumulation of volatile fatty acids (VFA), which can cause lowering the pH. For pH stability is important CO2-bicarbonate to be equilibrium. In order to enable some reactions necessary association between methanogenic and Acetogenic bacteria, creating bacterial aggregates of these different populations (Boyd R., 2000, pp. 7).

This implies that the starts of the reactors are generally slow, requiring time may be of the order of months. In general, the process speed is limited by the ...