Ammonia-free emissions from an engine system fueled with ammonia and hydrogen during cold-start and warm-up periods are demonstrated. The fuels are supplied into a single-cylinder test engine under constant-speed conditions. The exhaust system consists of a redox catalyst followed by an in-line adsorber, the latter of which stores the ammonia that flows through the former. The results show that all adsorbers, H-ZSM-5, Cu-ZSM-5, and Pt-ZSM-5, can adsorb ammonia during cold-start conditions although the engine should be operated with retarded spark timing and a high hydrogen ratio because of low combustion efficiency at low coolant temperatures. Cu-ZSM-5 and Pt-ZSM-5 are regenerated after adsorption through their catalytic reactions without ammonia slip. Cu-ZSM-5, which has the largest adsorption capacity among the tested adsorbers, favors lean burn operation for regeneration. Pt-ZSM-5 has the advantage of simple regeneration control. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.