Green House Gases (GHGs) are those that can absorb and emit infrared radiation. There are six Green House Gases as identified under the Kyoto protocol. These are:- Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs); and Sulphur hexafluoride (SF6). While creating the GHG inventory of the organization, there is a need to calculate all the six GHGs e.g. GHG emissions from the burning of fossil fuels, methane emission from anaerobic digestion of organic matter (Spent wash treatment in anaerobic digester in molasses based distillery), CO2 emission from use of fire extinguishers during actual fire conditions or emergency preparedness programs/training in the organization, etc.
Clause 4.3.3 of ISO 14064-1 specifications suggests that organization shall select and use quantification methodologies that will reasonably minimize uncertainty and yield accurate, consistent and reproducible results. ISO 14064-1 specifies that organization shall calculate their GHG emission as per six greenhouse gases separately. The same method is given in following schematic;
Therefore, whatever the source of Green House Gasses and the calculation methodology, the resulting value should be in mass unit of Carbon dioxide equivalent form. By multiplying the resulting value of gas other than CO2 with the respective Global Warming Potentials (GWP) will result in CO2 equivalent form. The concept of global warming potential (GWP) has been developed in order to enable comparison of the ability of different GHGs to trap heat in the atmosphere (Read more on GWP here). Following table shows GWP of different GHGs;
Following examples will provide calculation methods as per the GHG protocol and ISO 14064-1;
Example 1: GHG emission from the burning of diesel in stationary source i.e. DG sets.
Burning of fuel in stationary source emits Methane and Nitrous oxide. To understand the further calculation process, let’s take 100 liters of diesel consumption in the DG set. The calculation would be;
CO2 emission = Fossil fuel consumption in volume unit X CO2 emission factor (Ton per volume unit)
CH4 emission = Fossil fuel consumption in volume unit X CH4 emission factor (Ton per volume unit)
N2O emission = Fossil fuel consumption in volume unit X N2O emission factor (Ton per volume unit)
Total GHG emission (in tCO2 eq) = (CO2 emission) + (CH4 emission X 21) + (N2O emission X 310)
CO2 emission = 100 X 0.00265
CH4 emission = 100 X 0.00000036
N2O emission = 100 X 0.000000021
Total GHG emission (in tCO2 eq) = 0.265299393 + (0.000035819 X 21) + (0.00000215 X 310)
Total GHG emission (in tCO2 eq) = 0.2667
Example 2: GHG emission from the use of R-134a [HFC – C2H2F4 (CH2FCF3)] from the air conditioning system
Conventional air conditioning systems uses HFC based referents which might leak HFC gas into the atmosphere. Let’s consider 100 kg of HFC leaked from the air conditioning systems, then how can we calculate GHG emission in CO2 equivalent form? The answer is here;
R-134a (HFC) = 100 Kg
Global Warming Potential of R-134a = 1300 t CO2 e per ton of R-134a
Total GHG emission (in tCO2 eq) = (100/1000) X 1300
Total GHG emission (in tCO2 eq) = 130
Note: For GHG emission factors, please refer IPCC GHG EF database
Shailesh is post graduate in Environment Management from Forest Research Institute (FRI) University, Dehradun, India. Presently he is working in the areas of Environmental and Renewable Energy Advisory Services. He has started GreenCleanGuide.com during his college days.