Historical emissions data were obtained from the UNFCCC GHG inventory and cover the period from 1990 to 2020 submitted in Common Reporting Format (Government of Japan, 2022).The submission to the UNFCCC is supplemented by the National Inventory Report data file, which provides sector-level emissions after allocation of electricity-related emissions to end-use sectors (Government of Japan, 2022).
NDC and other targets
The target emission level in 2030 provided in the updated NDC submitted in October 2021 is directly used in this assessment.
Current policy projections
Energy-related CO2 emissions
For the analysis of current policy projections, we used the IEA World Energy Outlook (WEO) 2021 Stated Policies Scenario (STEPS) as a basis (IEA, 2021b). The WEO STEPS reflects both implemented policies as well as announced policies. For Japan, the emission scenario mainly comprises of implemented policies as at mid-2021 (see Annex B.6 of WEO 2021); only for the power sector the electricity mix targets of the updated NDC and the 6th Strategic Energy Plan (METI, 2021d) were assumed to be fully achieved.
Since it is premature to assume that the 2030 electricity mix targets would fully be achieved, we explored different shares of renewable and nuclear power generation based on historical trends, estimates by external studies, and current status of nuclear reactor safety examinations. CO2 emissions from the power sector were re-calculated based on the low and high emission electricity mix cases described below.
In the low emissions case, we assumed that:
- Nuclear power generation share will reach 20%, the lower range of the 2030 target, as projected in the WEO2021 STEPS. The nuclear capacity in operation will reach 30 GW, which will be larger than the total of 25 reactors that have applied for restart and two reactors under construction that applied for future operation to the Nuclear Regulation Authority as of September 2022 (JAIF, 2022).
- Coal and oil power shares are kept to the NDC target (coal: 19%, oil: 2%).
- Renewable electricity generation reaches 315 TWh/year in 2030, assuming a linear extrapolation of trends between 2012 and 2021 out to 2030 (IEA, 2022). The resulting share in total generation is 32 %, thus falling short of the 36-38 % target.
- Gas power meets the remaining demand. The resulting share in total generation is 25%.
In the high emissions case, we assumed that:
- All 27 reactors that have applied for restart (or future start of operation for plants under construction) as of September 2022 will be in operation by 2030 but only at the capacity factor of 49% (the 2021 level), taking into account the possible court cases and unplanned inspections. The resulting share in total generation is 9%.
- Oil power shares kept to the NDC target (2%).
- Renewable energy share reaches 301 TWh/year in 2030 as estimated by Asano and Obane (Asano & Obane, 2020). The resulting share in total generation is 31 %, falling short of the 36-38% target.
- Gas and coal power meets the remaining demand with equal shares, leading to 28% share each.
After the recalculation of the 2030 electricity mix, CO2 emissions in 2030 were recalculated— CO2 emission factors per technology were assumed to be identical to those in the WEO 2021 STEPS.
The projections for Industrial process CO2 emissions were based on the growth rates between 2020 and 2030 from the IEA WEO 2021 STEPS, multiplied by the 2020 emissions from the UNFCCC GHG inventory (IEA, 2021b). For the emissions of agriculture and waste CO2, CH4 and N2O, we linearly extrapolated historical trends of two different emission intensity indicators: per unit GDP and per capita, into future years.
For both intensity indicators, the historical trends observed between 2010 and 2020 were linearly extrapolated to 2030. The GDP growth projections up to 2030 were taken from IEA (IEA, 2021b) and population projections were taken from UN Population Prospects (medium fertility variant) (UN DESA, 2022). The 2030 projections using different emission intensity indicators were similar.
For F-gas emissions, the expected impacts of the Act on Rational Use and Proper Management of Fluorocarbons (2013 amendment) to enhance management of F-gas use as well as the Ozone Layer Protection Act (‘F-gas Act’, 2018 amendment) to regulate the production and imports of F-gases to comply with the Kigali Amendment were considered. Our calculations show that the HFC emission levels are projected to fall far short of the levels targeted under the updated NDC.
As described in the current policy projections section, the F-gas Act has not been successful in improving the recovery rate of refrigerants from end-of-life refrigeration and air conditioning equipment which was 41% against the targeted rate of 50% in 2020 (METI; MOEJ, 2021). Based on the historical trends reported in METI and MOEJ (METI; MOEJ, 2021), we assume that the HFC recovery rate will not improve over time. We also assume that the leakage rates for the in-use stock will also not improve under current policies. Regarding the 2018 amendment of the Ozone Layer Protection Act, the business-as-usual consumption levels are projected to be below the Kigali cap at least until 2025 (METI, 2018a): the Kigali cap for Japan becomes significantly lower only in 2029. Since there is some time lag between consumption and emissions, we assume that the amended Ozone Layer Protection Act will not affect the HFC emission levels up to 2030.
The point of departure for the revised F-gas emission projections is the business-as-usual (BAU) projections provided in the background document of the Plan for Global Warming Countermeasures (MOEJ, 2016a) – the Plan projects F-gas emissions to increase from 39 MtCO2e/year in 2013 to 77 MtCO2e/year in 2030 under a BAU scenario. The three measures: (i) enhanced recovery from end-of-life equipment, (ii) avoidance of leakage from in-use equipment, and (iii) switch to lower GWP F-gas and non-F-gas refrigerants are expected to reduce emissions to the NDC target level of 29 MtCO2e/year in 2030. In our assessment, we assume that only part of the NDC implementation plan, i.e. the switch to lower GWP F-gas and non-F-gas refrigerants, would be achieved.
Global Warming Potentials
The CAT uses Global Warming Potential (GWP) values from the IPCC's Fourth Assessment Report (AR4) for all its figures and time series. Assessments completed prior to December 2018 (COP24) used GWP values from the Second Assessment Report (SAR).