Production of coke required for steel manufacturing generates coke oven gas (COG) as by-product. Cleaning of COG yields an aqueous waste stream containing ammonia, water, phenol, carbon dioxide and trace components. Currently, this waste stream is disposed of by incineration. Due to the presence of carbon dioxide, a significant fraction of the ammonia is present as ammonium carbonate, (NH4)2CO3. This work investigates the utilisation of aqueous (NH4)2CO3 in a commercially-available solid oxide cell at 750 °C. The cell performance was characterised by current-voltage (I-V) curves and was shown to have excellent electrical performance in electrolysis mode. Online quadrupole mass spectrometry (QMS) measurements show (NH4)2CO3 catalytically decomposed to form nitrogen, hydrogen and carbon dioxide, with electrolysis at 1.4 V increasing hydrogen production by 50 vol%. The cell had very good performance in fuel cell mode, although this was tempered due to OCV losses caused by the carbon dioxide present.