Post updated to include a geothermal power replacement scenario, adjust costs for coal-fired power plants, correct a land area figure, and outline major assumptions utilized in calculations.

Phasing out Japan's nuclear fleet would increase carbon emissions by at least 414 million tons, a 10% increase over current carbon emissions, as the country shifts electricity generation to more carbon-intensive LNG and coal-fired power plants. Replacing projected nuclear power generation in 2030 with power from coal or LNG would add at least 25% and as much as 37% of current emissions to the country's future carbon output.

As Japan struggles to resolve the ongoing crisis at its Fukushima Daichi nuclear complex, the implications of the crisis on the future of nuclear power remain unclear. Japan, a country with few domestic energy resources, relies heavily on nuclear power production to meet its electricity demands. In 2009, nuclear power was responsible for 27% of domestic electricity generation.

Before the crisis at Fukushima, Japan aimed to roughly double its nuclear capacity by 2030 to provide 50% of its total electricity generation. This expansion of nuclear power was a key component of the nation's climate change mitigation efforts, which include a targeted 25% reduction in CO2 emissions relative to 1990 levels by the year 2020.

Phasing Out Current Nuclear Generation

If Japan were to phase out its nuclear power fleet, it would likely ramp up production from its natural gas-fired and coal power plants. The country is already dependent on natural gas and coal for the majority of its electricity generation, as roughly 26 percent of the country's electricity comes from natural gas, and another 28 percent from coal. The number of natural gas plants in the country increases yearly, and Japan remains the world's largest importer of both liquefied natural gas and coal.

Below, we've estimated the impact on overall current carbon emissions if Japan were to completely phase out production of electricity from its current fleet of nuclear reactors. Three scenarios project the effect of replacing lost generation either entirely by coal generation, entirely by generation from liquefied natural gas, or by an equal split of both.

If nuclear power were to be completely taken out of Japan's power supply, the country's carbon emissions would rise by at least 414 million tons over current emissions. Carbon emissions would increase by at least 10% and as much as 17% across the entire economy, while power-sector emissions would soar by 29% to 49%, depending on the mix of replacement power.

(For exact numbers, see Chart 1 at the end of this post)

These scenarios would have a profound impact not only on the country's carbon emissions, but also on its trade surplus. In 2009, Japan imported 182 million short tons of coal, mostly from Australia, and was the world's largest consumer of Liquefied Natural Gas (LNG), importing about 64.5 million tons. Scenario 1, which considers the replacement of nuclear with coal-fired generation, would cost Japan $11.2 billion dollars in imports, cutting the country's current trade surplus by 24 percent. The additional imports required under Scenario 2, which assumes the replacement of nuclear generation entirely through LNG-fueled natural gas plants, would cost the country an additional $17.5 billion dollars, decreasing Japan's trade surplus by 37.6 percent.

As well, construction costs for LNG and coal-fired plants to be able to generate this additional electricity would be substantial. Construction costs for new LNG plants would fall around $41 billion (using an estimate of $1,200/KWe) , while costs for new coal-fired power plants would amount to $101 billion dollars (using an estimate of $3000/KWe).

What About Replacement From Renewables?

Replacing the generation lost from a complete phase-out of nuclear power entirely with solar energy would require a more than a hundred-fold increase in solar's contribution to the national energy system, from the country's 2009 electricity generation of 2.1 billion kWh (0.2% of total electricity) to 267.8 billion kWh (27% of total electricity).

Furthermore, the 203 gigawatts (GW) of installed solar capacity required to replace Japan's current nuclear fleet would cover roughly 1.3 million acres, according to a land area calculator created by the National Renewable Energy Laboratory (NREL) in the United States.

Using an estimate of $5 per watt of installed solar PV capacity, installing this 203 GW of solar capacity would cost the country at least $1.01 trillion dollars.

Alternatively, replacing the generation lost from a complete phase-out of nuclear power entirely with wind energy would require wind generation to increase from its current levels, 3.257 billion kWh (0.3% of total electricity), to 267 billion kWh (27% of total electricity).

This would require 152 GW of installed wind capacity, at a total installation cost of $375 billion (using an estimate of $2,466/KWe). According to NREL's wind farm area calculator, the installation of these wind turbines would require 38,000 acres taken out of production on a wind farm, and a total of 1.3 million acres for the entire wind farm.

Finally, replacing current nuclear generation with geothermal energy would require a nearly hundred-fold increase in geothermal's contribution to the country's energy supply, from the 2.75 billion kWh it currently generates, to 259.5 billion kWh annually.

Using an estimate of $4,100 kWh for construction costs of geothermal plants, this translates into about $175.5 billion dollars to construct the 42,804 MW of installed capacity necessary to generate the electricity lost from a complete nuclear phase-out.

Phasing Out Nuclear Generation by 2030

To meet its climate commitments, Japan has pledged to roughly double its nuclear capacity by 2030, with plans to derive 50% of total electricity generation from nuclear power by that date. Japan has one of the lowest projected annual electricity demand growth rates, estimated by the EIA at an average of 0.7 percent. Additionally, Japan is one of the only countries whose energy-related carbon dioxide emissions are projected to decline, specifically by an average of 0.6 percent per year until 2035.

Below, we estimate the rise in carbon emissions that would accrue if the country's expected nuclear generation in 2030 were replaced by imports of coal, LNG, or an equal split of both.

Phasing out nuclear generation from the country's power supply and replacing it with either LNG or coal would present a significant setback as the nation strives to reduce overall CO2 emissions by 25% below 1990 levels by 2020. Instead, overall carbon dioxide emissions would increase by at least 270 million tons, 22 percent of Japan's current total emissions. If Japan replaced all of this lost generation with electricity from coal-fired power plants, the country's C02 emissions would rise by at least 452 million tons, 37 percent of current total emissions and an immense 109 percent of current power sector emissions.

(For exact numbers, view Chart 2 at the end of this post)

The additional LNG imports required by Scenario 1 would cost the country $38.8 billion, which would represent an 83% decrease in Japan's current trade surplus, while the coal imports required by Scenario 2 are estimated to cost almost $25 billion dollars, which represents a 53% decrease in Japan's current trade surplus.

The cost of construction of enough new LNG-fired plants to power this electricity generation would total $86 billion, while the equivalent cost of construction of new coal-fired power plants would total $217 billion.

Replacement with Renewables

To avoid these emissions increases and replace lost generation through solar power, Japan would have to generate 568 million kWh of solar power annually. With an assumed capacity factor for the country of 15 percent, this would require an installed solar capacity of 432 GW, more than four times the country's planned goal of 53GW of solar PV capacity by 2030. Installation of this solar PV capacity would cost an estimated $2.16 trillion dollars, and cover roughly 2.77 million acres.

Replacing Japan's 2030 nuclear plans with generation from wind installations would require 568 million MWh of wind energy, a significant increase from the 3.57 million MWh currently generated by the country's wind installations.

The installation of this 324 GW of wind turbines would cost around $798 billion, and would require 81,141 acres. Again, this number represents the area taken out of production on a wind farm, but the wind farm itself would need to be as large as 2.8 million acres.

Finally, the replacement of the country's planned 2030 nuclear generation would require a geothermal power installed capacity of 94,857 MW, at a cost of about $388.9 billion.

Correction: the original post contained a total land area figure for Japan drawn from an erroneous source. The post was updated on April 11th to correct this error.

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Major Assumptions