INGENIEUR
Tier 1 Data from national / international energy statistics and default emission factors ;
Tier 2
Tier 3
Data from national energy statistics , together with country-specific emission factors , where possible , derived from national fuel characteristics ; and
Statistics and data on combustion technologies applied together with technologyspecific emission factors ; this includes the use of models and facility-level emission data where available .
Figure 2 : 2006 IPCC estimating emissions from fossil fuel combustion .
Guidelines estimate GHG emissions separately in terms of the species . The Tier 1 approach accounts for emissions by relating national activity data with default emission factors . In the context of energy generation , emission factors are dependent only on fuel type and disregard quality of fuel and technology . The Tier 2 approach takes into account the national fuel characteristics by utilising country-specific emission factors . The Tier 3 approach goes further to take into consideration technology and facility-level emission data . While higher tiers will ensure more representative data being generated , resource and expertise required for data collection and reporting could be a challenge for developing economies where the infrastructure and policies are not in place .
Generally , GHG emissions are estimated using the following equation which converts the quantity of fuel consumed with an appropriate emission factor for a specific fuel .
GHG = Σ i , j ( F i
• NCV i
• ρ i
• EF ij
• GWP j
) where : GHG : GHG emissions due to the fuel used ( kg
CO 2 eq / year ),
F i
: quantity of the fuel type “ i ” used in the reference period ( L / year ),
NCV i
: net calorific value of the fuel type “ i ” ( J / kg ), ρ i
: fuel type “ i ” density ( kg / l ),
GWP j
: Global warming potential of “ j ” greenhouse gas ( kgCO 2
/ kgGHG j ),
EF ij
: emission factor ( on NCV basis ) for the fuel type “ i ” ( kgGHG j / J ), i : fuel type , and j : greenhouse gas type .
Although the 2006 IPCC Guidelines provide default values , applying country-specific emission factors is recommended when estimating national greenhouse gas emissions
( IPCC , 2006 ) to achieve a more representative reporting . According to United States Agency for International Development ( USAID ), under the Low Emission Asian Development ( LEAD ) Programme 2013 , the need to develop countryspecific emission factors is mainly because the default emission factors provided by IPCC do not reflect the exact values for each country because conditions may vary and this is the main source of uncertainty with national GHG inventories . To obtain an accurate estimation of GHG emissions , fuel density , net calorific values and countryspecific emission factors should be determined locally through extensive experimental analyses . There have been ongoing scholarly studies on developing CHG emission factors in several countries around the globe to estimate actual CHG emissions of combustion systems with the Tier 2 method , which consider the characteristics of national fuels ( Quick and Glick , 2000 ; Sheng and Li , 2008 ).
Jeon et . al . ( 2010 ) reported that CO 2 emission factors mainly depend on the carbon content of the fuel rather than combustion conditions . Emission factors are used to relate the emission from sources to a common activity level associated with those emissions . Emission factors are derived from measured data , either experimentally or collected over a specific period . Emission factors are typically expressed as ratios ; for example , the weight of a substance emitted ( i . e . CO 2
, CH 4 , N 2
O , etc .), denominated by the unit weight , volume , distance , or duration of the activity emitting the substance ( EPA , 1999 ). To estimate emissions , the emission factors are multiplied by the activity level , which may be determined by direct data collected from relevant facilities .
In this TNB Research project , both fuel and fuel data were analysed to develop the country-
28 VOL 87 JULY-SEPTEMBER 2021