Anaerobic slurry co-digestion of poultry manure and straw: effect of organic loading and temperature

Azadeh Babaee,Jalal Shayegan,Anis Roshani

doi:10.1186/2052-336x-11-15

Abstract

In order to obtain basic design criteria for anaerobic digestion of a mixture of poultry manure and wheat straw, the effects of different temperatures and organic loading rates on the biogas yield and methane contents were evaluated. Since poultry manure is a poor substrate, in term of the availability of the nutrients, external supplementation of carbon has to be regularly performed, in order to achieve a stable and efficient process. The complete-mix, pilot-scale digester with working volume of 70 L was used. The digestion operated at 25°C, 30°C and 35°C with organic loading rates of 1.0, 2.0, 2.5, 3.0, 3.5 and 4.0 kg Volatile solid/m3d and a HRT of 15 days. At a temperature of 35°C, the methane yield was increased by 43% compared to 25°C. Anaerobic co-digestion appeared feasible with a loading rate of 3.0 kg VS/m3d at 35°C. At this state, the specific methane yield was calculated about 0.12 m3/kg VS with a methane content of 53–70.2% in the biogas. The volatile solid (VS) removal was 72%. As a result of volatile fatty acid accumulation and decrease in pH, when the loading rate was less than 1 or greater than 4 kg VS/m3d, the process was inhibited or overloaded, respectively. Both the lower and higher loading rates resulted in a decline in the methane yield.

Highlights

In the past few decades, the large amounts of animal manure and slurries have been produced by the animal breeding sector as well as the wet organic waste streams represent a constant pollution risk with a potential negative impact on the environmental, if not managed optimally
The contents of the reactor were mixed as controlled by a timer, which was activated for 30 min every hour
The study clearly indicates that anaerobic digestion is one of the most effective biological processes to treat a wide variety of solid organic waste products

Summary

Introduction

In the past few decades, the large amounts of animal manure and slurries have been produced by the animal breeding sector as well as the wet organic waste streams represent a constant pollution risk with a potential negative impact on the environmental, if not managed optimally. When untreated or poorly managed, animal manure becomes a major source of air and water pollution. The animal production sector is responsible for 18% of the overall greenhouse gas emissions, measured in CO2 equivalent and for 37% of the anthropogenic methane, which has 23 times the global warming potential of CO2 [2]. Approximately 400 million tons of wastes have been produced by Iran livestock industry (cattle and poultry) and agriculture sector. It means that it really needs an integrated waste management

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