This research evaluated the amount of greenhouse gas (GHGs) emissions from wastewater of the central wastewater treatment system at Mahidol University, Salaya campus, during the in years 2009-2012 by comparing two treatment systems: an oxidation pond and an extended aeration activated sludge. Researchers used the equation from the guidelines of the clean development mechanism (CDM) compares with the equation from carbon footprint for organizations (CPO). In addition, this research also studied the potential of biogas production to estimate the amount of GHGs that can be reduced when biogas technology is applied. The result showed that the oxidation pond caused more methane emission than the extended aeration activated sludge system. GHGs emissions from wastewater using CDM method were lower than the one used by Intergovernmental Panel on Climate Change: IPCC (2006). This difference was due to IPCC method guidelines including the calculation of nitrous oxide emissions, which has a global warming potential (GWP) several times higher than CH4. Furthermore, concerning the potential to produce biogas from, wastewater from the aeration pond caused the maximum release of methane, while wastewater before entering to system caused minimal emissions due to the decomposition of organic substances occurring in a short time.