Use of Models and Facility-Level Data in Greenhouse Gas Inventories

Use of Models and Facility-Level Data in Greenhouse Gas Inventories
• Assume inventory Tier 2 approach (or Tier 1 in special circumstances) is typical of the plant without
specific data;
• Find a relationship between the facility-level data and some features of each facility and use this to
model the emissions for facilities without data (“Surrogate Data”);
• Use inventory approach to estimate category emissions and disaggregate this by facility-level data.
The choices made by inventory compilers regarding the use of facility-level data require the use of expert judgement. In
some countries, steps are being taken to develop frameworks to make better use of available evidence to support these
judgements and to encourage consistent decision making across sources. The IPCC plans to continue its efforts to
explore and support the development of such frameworks in its future work programme.
4.3.5 Time series consistency
In general, facility-level data are not available for all inventory years. In order to achieve a consistent time series it is
necessary to splice facility-level data with traditional category level estimates. The IPCC Guidelines give guidance on
how to do this. (See Chapter 5 “Time Series Consistency”, Volume 1, 2006 IPCC Guidelines for guidance on time series
consistency, noting especially Section 5.3.3.6 “Selecting the most appropriate technique”.)
The participants noted that an overlap of several years worth of data will improve the splicing of the two data sources. As
additional years data are collected this splicing should be reviewed. It is also possible that as experience in the
production of facility-level data improves the quality of the facility-level data may improve.
In order to recalculate earlier years data based on facility-level data, an issue to consider is the changes in technology
and practices that may have occurred.
It may be the case that facility-level data are not collected annually. This could pose particular problems for time series
consistency. Data collected less than annually should be reviewed carefully against the criteria outlined above and the
inventory compiler should evaluate if, and if so how, the data could be incorporated into the inventory. If it is determined
that it is not appropriate to use the data in the national inventory, the data may still be valuable for QA/QC.
4.4 Energy data
4.4.1 Aligning facility-level fuel and IPCC fuel types
The types of fuels reported in facility-level data may be clear, and the inventory compilers may be able to map the facility
fuel data to one of the standard IPCC fuel types. In some cases, the fuels in the facility-level data may be ambiguous,
and may not match the standard set of IPCC fuel types. In this case:
• Clarification could be sought from the operators of the facility about the nature of fuels being used to try and
remove the ambiguity.
• A decision will need to be taken about the appropriate mapping to use between the facility-level data fuel type
and the IPCC fuel type where ambiguity remains.
• Or if the ambiguity is too great, then the inventory compilers may choose not to include the facility-level data in
the inventory at all.
4.4.2 Ensuring biogenic carbon can be separated
Biomass is now quite commonly used in combination with fossil fuels
or indeed as a primary fuel. In Energy Sector in a national
greenhouse gas inventory, CO 2 emissions from biogenic carbon
should be reported as an information item separately from national
total emissions. Facility-level reporting of emissions may include
emissions from biogenic carbon, and so these data need careful
examination to ensure that emissions from fossil fuel and biomass
are correctly reported.
4.4.3 Consistency with energy statistics for the country
Estimates of emissions in the inventories often rely heavily on
national energy statistics. If energy data reported from facilities were
to be used in an inventory, it is important to understand the reasons
Example for EU-ETS
Emissions reported under the EU ETS
should exclude emissions from bio-carbon.
However, inventory compilers should be
aware that the raw emissions data taken
from the more detailed ETS show instances
of companies reporting emissions from biocarbon
use – either these are errors in the
data, or more probably they represent
emissions of fossil carbon from fuels that
are mixtures of bio-fuels and fossil fuels.
IPCC Expert Meeting Report 22 TFI