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  Japan needs Nuclear Power to Reduce CO2 Emissions

Down the learning Curve with Emerging Technologies

Briefing Note on the Kyoto Protocol

Japan needs Nuclear Power to Reduce CO2 emissions

Markal ‘‘most widely used’’ model, but...

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Figure 7. Carbon dioxide emission trajectories in the MARKAL model of Japan as additional reduction measures are taken.

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Figure 8. Major reductions in carbon dioxide emissions in the MARKAL model of Japan stern from the electricity sector through the natural gas and nuclear power.


A study was made of the Japanese energy system using the MARKAL model to determine what technologies are needed to reduce future carbon dioxide emissions. Nuclear energy can make the greatest reduction by the year 2010, and is essential to further reduce emissions below the 1990 level. Continued expansion of nuclear power after 2010, together with energy conservation, renew- ables, and especially greater use of natural gas, would continue to lower emissions. Even with a choice of the more than 200 energy technologies considered in the model, however, no drastic emission reduction can be achieved in Japan with the assumed growth in energy and the national economy.

Nuclear energy’s potential for long-term emission reduction was evaluated by improving the database used in the Japanese model for the ETSAP Annex VI common assessment and extending the model time horizon to 2050.

Energy conservation measures considered by the model included efficiency improvements and new technology in the industrial and trans portation sectors, insulation and efficiency improvements in the residential and commercial sectors, and combined cycle and combined heat-and-power generation of electricity. Renewables included solar and geothermal energy for electricity and heat, and biomass for electricity and fuel. To reduce carbon dioxide emissions, the model can also switch from coal to oil to natural gas by changing technologies.

Nuclear energy is represented in the model by light-water and fast breeder reactors, and by high temperature gas reactors used to produce hydrogen as a fuel and heat at temperatures as high as 850 degrees C.

For the model runs, it was assumed that GDP would grow at 2.5% from 2000 to 2010, 1.75% to 2030, and 1.2% to 2050. Passenger traffic is expected to increase by 70 percent during the 50 years, and freight traffic by about half. Steel and cement production would decline about 15 percent.

The model sets an upper limit to the importation of oil, declining by one-quarter from its year 2000 level by 2050. Liquefied natural gas, on the other hand, may expand to triple its year 2000 value. The sources of carbon dioxide emission reductions were identified through a series of model runs in which greater use of natural gas and nuclear power were introduced, together with a penalty on emissions. The resulting carbon dioxide emission trajectories are shown in Figure 7.

A reference run, Case A, was made with no restriction on carbon dioxide emissions, allowing no nuclear investment after 2001, and energy and technology choices made only from an economical viewpoint. Under these circumstances, the use of coal would expand to become the dominant source of electricity and account for more than half the supply of primary energy. Japanese carbon dioxide emissions would be double their 1990 level by 2050.

For Case B, with the same restriction on nuclear energy, a penalty of carbon dioxide emission was introduced increasing from 5,000 yen per ton of carbon dioxide in 2005 to 50,000 yen per ton by 2050. In this case, the use of natural gas continues to expand, supplanting more than half of the coal for electric power generation by 2050. Carbon dioxide emissions would continue to grow but by 2050 they would be one-third less than in Case A.

In Case C, the assumed limitation on importing natural gas is removed after the year 2020. In this case, natural gas completely supplants coal for electric power generation by 2040 and accounts for half of Japan’s primary energy by 2050. Carbon dioxide emissions level off and begin a slight decline after the year 2015.

For Case D, nuclear power, which had been assumed to phase out in the previous cases, is allowed to expand from 46 GWe capacity in 2000 to 125 GWe in 2050. With virtually no carbon dioxide emissions from nuclear power, Japan’s carbon dioxide emissions level off about 15 years sooner and 10 percent lower than without nuclear. Then there is a gradual decline in emissions as nuclear begins to replace natural gas for generating electricity until they fuel about equal amounts of electricity by 2050.

Finally, in Case E, future high-temperature gas rectors are assumed to provide industrial process heat. This leads to a continuing decline in carbon dioxide emissions after about 2040 when they would otherwise level off.

The major reductions in carbon dioxide emissions stem from the electricity sector through the use of natural gas and nuclear power, as shown in Figure 8.

These model results were reported by Osamu Sato of the Japan Atomic Energy Research Institute at the ETSAP workshop in November 1997. They suggest that Japan will have difficulty in achieving the 6 percent reduction in greenhouse gas emissions during the 2008-2012 time period called for by the Kyoto Protocol strictly with domestic emission reductions. Thus, Japan seems likely to seek emissions trading opportunities under the Protocol that enable it to achieve additional emission reductions elsewhere.

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