Effects　of　carrier　gas　composition　(N-2/air)　on　NH3　production,　energy　efficiency　regarding　NH3　production　and　byproducts　formation　from　plasma-catalytic　decomposition　of　urea　were　systematically　investigated　using　an　Al2O3-packed　dielectric　barrier　discharge　(DBD)　reactor　at　room　temperature.　Results　show　that　the　presence　of　O-2　in　the　carrier　gas　accelerates　the　conversion　of　urea　but　leads　to　less　generation　of　NH3.　The　final　yield　of　NH3　in　the　gas　phase　decreased　from　70.5%,　78.7%,　66.6%　and　67.2%　to　54.1%,　51.7/e,　49.6%　and　53.4%　for　applied　voltages　of　17,　19,　21　and　23　kV,　respectively　when　air　was　used　as　the　carrier　gas　instead　of　N-2.　From　the　viewpoint　of　energy　savings,　however,　air　carrier　gas　is　better　than　N-2　due　to　reduced　energy　consumption　and　increased　energy　efficiency　for　decomposition　of　a　fixed　amount　of　urea.　Carrier　gas　composition　has　little　influence　on　the　major　decomposition　pathways　of　urea　under　the　synergetic　effects　of　plasma　and　Al2O3　catalyst　to　give　NH3　and　CO2　as　the　main　products.　Compared　to　a　small　amount　of　N2O　formed　with　N-2　as　the　carrier　gas,　however,　more　byproducts　including　N2O　and　NO2　in　the　gas　phase　and　NH4NO3　in　solid　deposits　were　produced　with　air　as　the　carrier　gas,　probably　due　to　the　unproductive　consumption　of　NH3,　the　possible　intermediate　HNCO　and　even　urea　by　the　abundant　active　oxygen　species　and　nitrogen　oxides　generated　in　air-DBD　plasma.　(C)　2017　The　Research　Center　for　Eco-Environmental　Sciences,　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.