EFFECT OF HEATING, MIXING AND DIGESTER TYPE ON BIOGAS PRODUCTION FROM BUFFALO DUNG

Abstract

Egypt has 3.43 million head buffalo and they produce about 3.5 million-ton/year of dung as air-dried material. The uncontrolled handling and storage of dung causes loss of organic matter, environmental pollution, methane emissive and a bad smell. The anaerobic digestion is one of the common technologies used for recycling organic wastes. Laboratory bench-scale biogas digester 22 liter capacity and 17 liter digestion volume (3 horizontals and 3 verticals type) were used for batch anaerobic digestion system of 95 day hydraulic retention time of buffalo dung 6.30 OTS% to study the effect of temperature, mixing and digester type on biogas production and methane content. The obtained results show that the biogas produced ranged between 104.7 to 468.1 L kg-1 organic total solid (OTS) while methane yield ranged between 69.2 to 284.1 L kg-1 OTS. The highest biogas yield was observed in vertical digester (468.1 L kg-1 OTS) compared to horizontal digester (353.1 L kg-1 OTS) in the cases of mixing and heating treatments. Meanwhile, the horizontal digester produced biogas (293.2 L kg-1 OTS) more than vertical digester (179.0 L kg-1 OTS) without mixing under room temperature. Similarly, the degradation percent of buffalo dung (expressed as organic carbon degradation, %) was increased in vertical digester compared to horizontal digester with mixing and temperature treatments. Consequently, the biogas and methane production were positively correlated with the temperature. Therefore, the maximum biogas yield was recorded in vertical digester with heating and mixing conditions. Maximum enhancement in biogas production over the control could be well correlated with maximum reduction in OTS and C/N ratio of buffalo dung manure. Therefore, we concluded that the amount of biogas production was not only depending on the type of digester but also affected by other parameters, i.e. mixing and heating conditions of the digester. The quantitative variations in biogas production were related with OTS, C, N and C/N ratio of the buffalo dung used.