Inline NH3 removal from biogas digesters

During biogas production from various types of substrates such as animal manure, fats and proteins, bacterial growth and biogas production can be inhibited by excessive ammonia (NH3) concentrations. If NH3 is removed from the biogas digester without damaging the digestion process, inhibition of the methane (CH4) producing bacteria will diminish. This study shows that it is possible to remove a significant quantity of NH3 from the biogas digester headspace and liquid phase by a simple gas circulation method where gas bubbles free of NH3 is forced through the upper 30 cm of the liquid phase in the biogas digester, into the headspace and out of the digester. The suggested method improves conditions for anaerobic bacteria exposed to high concentrations of NH3 by simply removing NH3 from the digester. l-scale biogas production the system presented in this study can be improved by circulating headspace gas through an ammonia absorber and returning the NH3 depleted biogas into the biogas digester. This method can also replace the need for mixing in biogas digesters.