The IPCC 2006 GL describe two tiers for estimating emissions. The bottom-up approach takes into account the time lag between consumption and emissions explicitly through emission factors. The top-down approach, the time lag is taking into account implicitly, by tracking the amount of virgin chemicals consumed in a year that replaces emissions from the previous year.
The web reporting system used in Slovakia allows calculating emissions in both approaches. The bottom-up approach is combined with the top-down approach. The procedure is as follows:
- Using the bottom-up approach (tier 2a) from the Logbook Leaklog;
- Calculation of the total consumptions of individual gases in Slovakia based on the Leaklog
(tier 2a); - Calculation of the total consumption of individual gases in Slovakia according to the top-down approach (tier 2b);
- Comparison of the total consumptions calculated by these two approaches;
- If differences above 2% occur, the data for bottom-up approach are corrected as follows (expert judgement based on the QA activity introduced in 2011):
- R134a: Difference is added to leakage from mobile AC,
- R404A: Difference is added between new charge/recharge 0.2/0.8,
- R407C: Difference is added to new charge of stationary AC,
- R410A: Difference is added to leakage from industrial refrigeration and stationary AC 0.1/0.9.
- If differences below 2% occur, the data for bottom-up approach are corrected proportionally according to the operational emissions.
- Calculation of emission estimates by the bottom-up approach using the corrected data.
Operational emissions: The approach described in the IPCC 2006 Guidelines assumes that servicing a facility replenishes the stock of a single chemical, and therefore the amount of gas used for servicing represents operational emissions. Slovakia has adopted this assumption with modification. Servicing a facility replenishes the stock of a chemical, and the amount of gas used for servicing equals emissions. However, facilities that are several years away from decommissioning are not serviced and the stock is not replenished for that facility. Therefore, operational emissions in this submission are composed of two members: (i) data from servicing facilities; (ii) emissions from non-serviced facilities several years away from decommissioning. The first member in operational emissions represents the consumption of gases for servicing and container management (these data are provided in Leaklog). It is assumed that the chemical used for servicing replenishes emissions from the stock, and therefore the stock of the