Roedd allyriadau o osodiadau sy'n rhan o Gynllun Masnachu Allyriadau'r UE (ETS) yn cyfrif am 51.6% o gyfanswm yr allyriadau nwyon tŷ gwydr yng Nghymru yn 2010; y prif gyfranwyr at yr allyriadau masnachu hyn oedd y sector Cyflenwi Ynni (y mae 92% o gyfanswm yr allyriadau o fewn Cynllun Masnachu Allyriadau'r UE, gan gynnwys pob gorsaf bŵer) a'r sector busnes (y mae 71% o gyfanswm allyriadau'r sector o fewn Cynllun Masnachu Allyriadau'r UE, gan gynnwys yr holl allyriadau o odynau sment a 83% o gyfanswm yr allyriadau sy'n deillio o gynhyrchu haearn a dur).
Emissions from installations participating in the EU Emission Trading Scheme (ETS) accounted for 51.6% of total GHG emissions in Wales in 2010; the main contributors to these traded emissions were the Energy Supply sector (of which 92% total emissions are within the EU ETS, including all power stations) and the Business sector (of which, 71% of total sector emissions are in the EU ETS, including all cement kiln emissions and 83% of total iron and steel production emissions).