Concern is worldwide about how to control the anthropogenic emissions of greenhouse gas (GHG) emissions. GHGs include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and are expressed as CO2 equivalents (CO2 eq.). On a 100-year basis, CH4 is 34 times as potent as CO2, while N2O is 298 times as potent as CO2, according to a 2013 Intergovernmental Panel on Climate Change. CO2 eq. is referred to as the global warming potential (GWP) of these gases.