From Pollutant to Fuel. A proof of principle for electricity production using nitrogen from sewage as a fuel

Abstract

The necessary removal of organically bound nitrogen and ammonium from sewage conventionally requires energy for aeration and reduces the potential biogas production in the following anaerobic stage due to the required carbon source for de-nitrification. It has recently been demonstrated that fuel cells can generate electricity, using ammonia as a fuel. The objective of this thesis research is to connect the necessity to remove organically bound-nitrogen and ammonium from sewage with the potential of reduced nitrogen, as incorporated in the compound ammonia, as a valuable and sustainable fuel for a fuel cell. The organically bound nitrogen present in sewage was converted into ammonium ions through anaerobic digestion in an Anaerobic Membrane BioReactor (AnMBR). These ammonium ions were separated from the AnMBR effluent using Ion Exchange (IE). Through a fractionized collection of the IE brine, the ammonium ions were concentrated and a distillation tower was used to further concentrate and convert the ammonium ions into a concentrated ammonia solution. This solution proved sufficiently rich in ammonia to be fed directly to a Solid Oxide Fuel Cell (SOFC), generating electricity. Thus, the described combination of technologies removed ammonium and organically bound nitrogen from the wastewater, producing an effluent with an extremely low ammonium concentration (