Vulnerabilities in the Production of Biogas from the Fat-Containing Tannery Waste

Abstract

Background. The problem of disposal of the fat-containing tannery waste can be solved by anaerobic fermentation. This raises the important question of the effect of inhibitor compounds on the process of methanogenesis and on the output of biogas. In particular, the effects of NaCl and NaHCO3 used in technology and antibiotics that accumulate in subcutaneous fat when used in animal husbandry for digestion of fat-containing raw materials have not yet been studied. Objective. The purpose of the paper is determination of possible influence of salts and antibiotics on the process of methanogenesis and on the output of biogas and methane. Methods. The study was conducted in laboratory reactors with a volume of 0.5 dm3 under anaerobic conditions at 38 ± 1 °С with the addition of different concentrations of salts and antibiotics (the sample was used without the addition of test compounds to control the process). The anaerobic association of microorganisms in the form of an inoculum served as the biological agent. Results. The effect of salt content on the destabilization of methanogenesis during digestion of fat-containing raw materials and the effect of the antibiotic content of tetracycline and norfloxacin on the yield of biogas from fatty raw materials were determined. Thus, with the use of NaCO3, the greatest inhibition occurs at a concentration of 11.4 g/dm3 (decrease in biogas output by 54%), with a further increase in the concentration to 22.8 g/dm3 an increase of 18.2% is observed compared to the concentration of 11.4 g/dm3. It is shown that the concentration of methane in biogas with the use of NaCO3 decreases with increasing concentration of the inhibitor, which confirms its negative impact on the process of methanogenesis. Conclusions. Biogas yield is increased by 17% at a NaCl concentration of 3.8 g/dm3, and biogas and methane production decreases even more at NaCl concentrations of 7.6 g/dm3. When using antibiotics, tetracycline and norfloxacin, the allowable rate in raw materials is 2.5 mg/dm3 for both antibiotics.

Keywords

• biogas
• fat-containing waste
• methane
• antibiotics
• salt