Decreased emission of nitrous oxide from delivery wards--case study in Sweden

The very potent greenhouse gas nitrous oxide (N₂O) is widely used as a mild anaesthetic for mothers in delivery work in Sweden. As a part of the Stockholm County Council environmental program it was decided in 2002 that the emissions should be drastically reduced. Different ways were theoretically evaluated, and catalytic splitting to nitrogen and oxygen gas (N₂ and O₂) was chosen for a demonstration installation. A Japanese commercial unit for treatment of mixed anaesthetic gases (Anesclean® from Showa Denko K.K.) was thoroughly modified and installed at the Karolinska University Hospital at Huddinge in Stockholm in 2004. The destruction of N₂O was optimised and studied for 2 years. Data from both collection and destruction are given in the article. Of the collected N₂O more than 95% was split to N₂ and O₂ in the very stable system. The overall emission decrease was mainly dependent on the share that could be collected in the specific exhaustion system as compared to the normal room ventilation. Life cycle assessment (LCA) and life cycle costing (LCC) were used to evaluate the actual environmental value and economical cost for the process. Important factors are pointed out.