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National Inventory Report, 1990-2004 - Greenhouse Gas Sources and Sinks in Canada

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ANNEX 1: KEY CATEGORIES

• A1.1 Key Categories - Methodology
  • A1.1.1 Summary Assessment
• A1.2 Key Category Tables
  • A1.2.1 Level Assessment without LULUCF
  • A1.2.2 Level Assessment with LULUCF
  • A1.2.3 Trend Assessment without LULUCF
  • A1.2.4 Trend Assessment with LULUCF
  • A1.2.5 Qualitative Assessment
• References

A1.1 KEY CATEGORIES - METHODOLOGY

Both the IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories (IPCC, 2000) and the IPCC Good Practice Guidance for Land Use, Land-Use Change and Forestry (IPCC, 2003) recommend as good practice the identification of key categories of emissions and removals. The intent is to help inventory agencies prioritize their efforts to improve overall estimates. A key category is defined as "one that is prioritized within the national inventory system because its estimate has a significant influence on a country's total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, or both" (IPCC, 2000).

This annex describes the key category analysis conducted for Canada's inventory, according to IPCC approaches.

Good practice first requires that inventories be disaggregated into categories from which key sources and sinks may be identified. Source and sink categories are defined according to the following guidelines:

• IPCC categories should be used with emissions specified in CO₂ equivalent units according to standard GWPs.
• A category should be identified for each gas emitted by the source, since the methods, emission factors, and related uncertainties differ for each gas.
• Source categories that use the same emission factors based on common assumptions should be aggregated before analysis.

The Canadian analysis of categories for key sources and sinks proceeds according to the Tier 1 Good Practice Guidance approaches of IPCC (2000, 2003). Using the Tier 1 method, key categories are first identified by quantitative methods using a predetermined cumulative emissions threshold. Second, Tier 1 key categories are determined by qualitative approaches. A more comprehensive Tier 2 approach is recommended if uncertainty estimates are available.

In this approach, the results of Tier 1 are multiplied by the relative uncertainty of the source and sink category. Since uncertainty estimates are not available for the LULUCF Sector, Tier 1 methods have been used for key category determination.

The quantitative approach identifies key categories from two perspectives. The first analyzes the emission contribution that each category makes to the national total (with and without LULUCF). The second perspective analyzes the trend of emission contributions from each category to identify where the greatest absolute changes (either increases or decreases) have taken place over a given time (with and without LULUCF). The percent contributions to both levels and trends in emissions are calculated and sorted from greatest to least. A cumulative total is calculated for both approaches. IPCC has determined that a cumulative contribution threshold of 95% for both level and trend assessments is a reasonable approximation of 90% uncertainty for the Tier 1 method of determining key categories (IPCC, 2000). The 95% cumulative contribution threshold has been used in this analysis to define an upper boundary for key category identification. Therefore, when source and/or sink contributions are sorted in decreasing order of importance, those that contribute to 95% of the cumulative total are considered quantitatively to be key.

Level contribution of each source is calculated according to Equation A1-1, which follows IPCC (2000), whereas Equation A1-2 is used to calculate the level contribution from both sources and sinks following IPCC (2003):

Equation A1-1 for source category level assessment:

L_x,t = E_x,t/E_t

where:

L_x,t = the level assessment for source x in year t

E_x,t = the emission (CO₂ eq) estimate of source category x in year t

E_t = the total inventory estimate (CO₂ eq) in year t

Equation A1-2 for source/sink category level assessment:

L_x,t* = E_x,t*/E_t*

where:

L_x,t* = level assessment for source or sink x in year t. The asterisk (*) indicates that contributions from all categories (including LULUCF) are entered as absolute values.

E_x,t* = | E_x,t |: absolute value of emission or removal estimate of source or sink category x in year t

E_t* = ∑_x | E_xt | : total contribution, which is the sum of the absolute values of emissions and removals in year t. The asterisk (*) indicates that contributions from all categories (including LULUCF) are entered as absolute values.

Trend contribution of each source is calculated according to Equation A1-3, which follows IPCC (2000), while Equation A1-4 is used to calculate the trend contribution from both sources and sinks following IPCC (2003):

Equation A1-3 for source category trend assessment:

T_x,t = L_x,t * | {[(E_x,t - E_x,0)/E_x,t] - [(E_t - E₀) / E_t]} |

where:

T_x,t = the contribution of the source category trend to the overall inventory trend (i.e., the trend assessment); the contribution is always recorded as an absolute value

L_x,t = the level assessment for source x in year t (derived in Equation A1-1)

E_x,t and E_x,0 = the emission estimates of source category x in years t and 0, respectively

E_t and E₀ = the total inventory estimates in years t and 0, respectively

Equation A1-4 for source and sink category trend assessment:

T_x,t = E_x,t^*/E_t * | {[(E_x,t - E_x,0)/E_x,t] - [(E_t - E₀)/E_t]} |

where:

T_x,t = trend assessment, which is the contribution of the source or sink category trend to the overall inventory trend. The trend assessment is always recorded as an absolute value, i.e., a negative value is always recorded as the equivalent positive value.

E_x,t^* = | E_x,t |: absolute value of emission or removal estimate of source or sink category x in year t

E_x,t and E_x,0 = real values of estimates of source or sink category x in years t and 0, respectively

E_t and E₀ = ∑_xE_x,t and ∑_xE_x,0 total inventory estimates in years t and 0, respectively. E_t and E₀ differ from E_t*and E₀* in Equation A1-2 in that the removals are not entered as absolute values.

The qualitative approach strengthens the foregoing quantitative analysis by considering more subjective criteria to determine if a category should be listed as key. In most cases, the application of these criteria identifies categories identical to those prioritized by the quantitative analysis. However, additional categories identified as key may be added to the primary list. IPCC Good Practice Guidance (IPCC, 2000) identifies four significant criteria for qualitative analysis. They are as follows:

1. Mitigation techniques and technologies: Identify those sources where emissions are being reduced significantly through the use of mitigation techniques or technologies.
   
   
2. High expected emissions growth: Identify sources with significant growth forecast.
   
   
3. High uncertainty: Identify most uncertain sources as key to help improve the accuracy of the inventory.
   
   
4. Unexpectedly low or high emissions: Identify calculation errors and discrepancies by doing order-of-magnitude checks.

This analysis uses three main sources of information to help define qualitative criteria. These published information sources provide valuable insight into qualitative key category assessment:

1. Canada's First National Climate Change Business Plan (NCCS, 2000a), Government of Canada Action Plan 2000 on Climate Change (Government of Canada, 2000), and Project Green - Moving Forward on Climate Change: A Plan for Honouring Our Kyoto Commitment (Government of Canada, 2005), outlining significant mitigation measures under way and planned in a range of sectors;
   
   
2. Natural Resources Canada's forecasts of GHG emissions from source categories for a Business-as- Usual (NRCan, 1999) and a Kyoto scenario (NCCS, 2000b); and
   
   
3. Quantitative Assessment of Uncertainty in Canada's National GHG Inventory Estimates for 2001 (ICF, 2004).

The overall purpose of identifying key categories is the institution of best practices in GHG inventory development. The appropriate aggregation of categories is crucial to reflect not only actual sources and sinks but also identical estimation procedures. Thus, while the UNFCCC CRF categories provide a basis for identifying sources and sinks, some aggregation of these sources and sinks can occur when using the same emission factors based on common estimation assumptions. In this analysis, major categories such as fuel combustion, fugitive emissions, industrial processes, agriculture, and waste are in keeping with the CRF. Within these major categories, the aggregation of subcategories occurs when estimates are made based on common assumptions about emission factors and on common activity data. For example, within the fuel combustion category, emissions from residential, commercial, and agriculture subsectors are combined.

In developing source and sink categories, it is also necessary to consider each GHG separately, since estimating methods, emission factors, and related uncertainties differ for each gas. Accordingly, source and sink categories are given for each major GHG - CO₂, CH₄, N₂O, HFCs, PFCs, and SF₆ - where that gas is a contributor to the national inventory.

A complete listing of all source and sink categories for the 2004 inventory is shown in Table A1-1.

TABLE A1-1: Key Source Category Analysis Summary, 2004 Inventory

Click here to view Table A1-1

A1.1.1 SUMMARY ASSESSMENT

The results of key category assessment in accordance with both IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories (IPCC, 2000) and the IPCC Good Practice Guidance for Land Use, Land-Use Change and Forestry (IPCC, 2003) are given in Table A1-1.

A1.2 KEY CATEGORY TABLES

A1.2.1 LEVEL ASSESSMENT WITHOUT LULUCF

Table A1-2 shows key categories indicated from level assessment without LULUCF, and Figure A1-1 shows the contribution of key categories to the level assessment.

TABLE A1-2: 2004 Key Categories by Level Assessment without LULUCF

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FIGURE A1-1: Contributions of Key Categories to Level Assessment without LULUCF

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A1.2.2 LEVEL ASSESSMENT WITH LULUCF

Table A1-3 shows key categories indicated from level assessment with LULUCF, and Figure A1-2 shows the contribution of key categories to the level assessment.

TABLE A1-3: 2004 Key Categories by Level Assessment with LULUCF

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FIGURE A1-2: Contributions of Key Categories to Level Assessment with LULUCF

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A1.2.3 TREND ASSESSMENT WITHOUT LULUCF

Table A1-4 shows key categories indicated from trend assessment without LULUCF, and Figure A1-3 shows the contribution of key categories to the trend assessment.

TABLE A1-4: 2004 Key Categories by Trend Assessment without LULUCF

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FIGURE A1-3: Contributions of Key Categories to Trend Assessment without LULUCF

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A1.2.4 TREND ASSESSMENT WITH LULUCF

Table A1-5 shows key categories indicated from trend assessment with LULUCF, and Figure A1-4 shows the contribution of key categories to the trend assessment.

TABLE A1-5: 2004 Key Categories by Trend Assessment with LULUCF

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FIGURE A1-4: Contributions of Key Categories to Trend Assessment with LULUCF

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A1.2.5 QUALITATIVE ASSESSMENT

A1.2.5.1 Mitigation Techniques and Technologies

Mitigation techniques are important for good practices, in particular if they are inclined to produce departures from the norm under which activity data and emission factors are estimated. Table A1-6 shows key categories identified as a result of having significant mitigation techniques and technologies introduced that have had (since 1990), or will have, an impact on emission estimates.

TABLE A1-6: Key Categories by Significant Mitigation Techniques and Technologies

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A1.2.5.2 High Emissions Growth

Table A1-7 shows key categories identified as a result of having emissions growth forecasts of over 20% between 1997 and 2020. Designation as key anticipates significant changes in the sector and indicates a need to establish sound estimating practices.

TABLE A1-7: Key Categories Identified from Anticipated High Emissions Growth

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A1.2.5.3 High Uncertainty

The ICF (2004, 2005) studies of uncertainty associated with 2001 inventory estimates are, with some exceptions, the most current sources of information on uncertainty levels. In these studies, uncertainties are reported following the UNFCCC CRF categories. Table A1-8 shows key categories identified as having a relatively high composite uncertainty (meaning both activity and emission factor uncertainties) compared with the expected norm (see estimates in the tables of Annex 7 and, where relevant, updates in Chapters 3-8).

REFERENCES

CPPI (2004), Economic and Environmental Impacts of Removing Sulphur from Canadian Gasoline and Distillate Production, Prepared by Levelton Consultants Ltd. in association with Purvin & Gertz Inc., Calgary, Alberta, Canada, August.

CSA (Online), Climate Change: GHG Registries, Canadian Standards Association. Available online at: www.ghgregistries.ca/index_e.cfm (accessed April 12, 2005).

Government of Canada (2000), Government of Canada Action Plan 2000 on Climate Change, Catalogue No. M22-135/2000E. Available online at: http://dsp-psd.pwgsc.gc.ca/Collection/M22-135-2000E.pdf.

Government of Canada (2005), Project Green - Moving Forward on Climate Change: A Plan for Honouring Our Kyoto Commitment, Catalogue No. En84-15/2005. Available online at: www.climatechange.gc.ca/kyoto_commitments/.

Hutchinson, J.J., P. Rochette, X. Verge, R. Desjardins, and D. Worth (2006), Uncertainties in Methane and Nitrous Oxide Emissions from Canadian Agroecosystems, Preliminary report submitted to the Greenhouse Gas Division, Environment Canada, by Research Branch, Agriculture and Agri-Food Canada.

ICF (2004), Quantitative Assessment of Uncertainty in Canada's National GHG Inventory Estimates for 2001, Final report submitted to the Greenhouse Gas Division, Environment Canada, by ICF Consulting, September.

ICF (2005), Quantitative Assessment of Uncertainty in Canada's National GHG Inventory Estimates for 2001: Supplementary Analysis, Final report submitted to the Greenhouse Gas Division, Environment Canada, by ICF Consulting, March.

IPCC (2000), Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories, Intergovernmental Panel on Climate Change National Greenhouse Gas Inventories Programme. Available online at: www.ipcc-nggip.iges.or.jp/public/gp/english/.

IPCC (2003), Good Practice Guidance for Land Use, Land-Use Change and Forestry, Intergovernmental Panel on Climate Change National Greenhouse Gas Inventories Programme. Available online at: www.ipcc-nggip.iges.or.jp/lulucf/gpglulucf_unedit.html.

Lauridson, S. (2004), Personal communication: E-mail dated September 24, 2004, from Invista (S. Lauridson) to the Greenhouse Gas Division, Environment Canada.

NCCS (2000a), Canada's First National Climate Change Business Plan, Canada's National Climate Change Process, National Climate Change Secretariat.

NCCS (2000b), An Assessment of the Economic and Environmental Implications for Canada of the Kyoto Protocol, Report prepared by the Analysis and Modelling Group, National Climate Change Process, National Climate Change Secretariat, November.

NRCan (1999), Canada's Emissions Outlook: An Update, Report prepared for the Analysis and Modelling Group, National Climate Change Process, Natural Resources Canada. Available online at: http://nrcan.gc.ca/es/ceo/update.htm.