Anaerobic Digestion and Codigestion of Chlorella Vulgaris Microalgae Biomass with Wastewater Sludge and Dairy Manure for Biogas Production

Saad H Ammar,Sadiq Riyadh Khodhair

doi:10.22153/kej.2017.03.001

Abstract

Abstract  Anaerobic digestion process of organic materials is biochemical decomposition process done by two types of digestion bacteria in the absence of oxygen resulting in the biogas production, which is produced as a waste product of digestion. The first type of bacteria is known as acidogenic which converts organic waste to fatty acids. The second type of bacteria is called methane creators or methanogenic which transforms the fatty acids to biogas (CH4 and CO2). The considerable amounts of biodegradable constitutes such as carbohydrates, lipids and proteins present in the microalgae biomass make it a suitable substrate for the anaerobic digestion or even co-digested with other organic wastes. The present work investigated methane biogas production by anaerobic codigestion of microalgae, Chlorella vulgaris biomass with organic waste from several sources such as wastewater sludge and dairy manure waste in different proportions as an additional carbon supply to enhance anaerobic digestion and therefore biogas production. Six bottles, employed as batch biodigesters each of 1 liter capacity, were used for that purpose at moderate conditions (35±2 oC). The produced biogas volume was monitored daily along 35 days and the results showed that the daily and cumulative biogas production was increased 4.5 times and 3 times for the bottles with 66.67% microalgae compared with the bottles with wastewater sludge or dairy manure waste only, respectively. Keywords: Anaerobic codigestion, biogas; dairy manure, microalgae Chlorella Vulgaris, wastewater sludge.

Highlights

Anaerobic digestion is biological process, occurring naturally in which a group of anaerobic microorganisms convert organic substrates or biowaste into biogas containing methane (CH4) and carbon dioxide (CO2) which is used as a renewable energy source [1].Biogas energy provides a lot of advantages
The bio-digestion of organic substances which contain mainly proteins, carbohydrates and fats takes place in four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. In this process a series of microorganisms called acidogenic bacteria converts the organic wastes which contain carbohydrates, proteins, oils, and cellulose to short chain organic acids such as propionic, butyric and acetic acids and CO2 and H2 gases and these organic acids are converted with H2 gas to biogas by another type of bacteria called methanogenic bacteria in the absence of oxygen [2].In more accurately, anaerobic digestion include more than two
The maximum daily biogas yields were 68 ml, 150 ml, and 300 ml for 250 ml microalgae + 500 ml wastewater sludge, 375 ml microalgae + 375 ml wastewater sludge and 500 ml microalgae + 250 ml at the 13th, 11th, and 6th day respectively, i.e. biogas yield increase with increasing microalgae proportion in the microalgae-wastewater sludge system. These results were better when compared with microalgae- dairy manure waste system at the same proportions as shown in Figs.8 and 9, this is due to high carbon content present in wastewater sludge [2]

Summary

Introduction

Anaerobic digestion is biological process, occurring naturally in which a group of anaerobic microorganisms convert organic substrates or biowaste into biogas containing methane (CH4) and carbon dioxide (CO2) which is used as a renewable energy source [1].Biogas energy provides a lot of advantages. The bio-digestion of organic substances which contain mainly proteins, carbohydrates and fats takes place in four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. In this process a series of microorganisms called acidogenic bacteria converts the organic wastes which contain carbohydrates, proteins, oils, and cellulose to short chain organic acids such as propionic, butyric and acetic acids and CO2 and H2 gases and these organic acids are converted with H2 gas to biogas by another type of bacteria called methanogenic bacteria in the absence of oxygen [2].In more accurately, anaerobic digestion include more than two

Methods

Results

Conclusion