How and why did fossil fuel use change in Fukushima Prefecture before and after the Great East Japan Earthquake?

The Great East Japan Earthquake (GEJE) in March 2011 greatly changed the spatial pattern of energy use in Fukushima Prefecture. The previously nuclear-reliant energy policy has transformed, with energy now generated mainly by fossil fuels and renewable sources. The spatio-temporal variation of fossil fuel use and the major causes of these changes have not previously been fully clarified.

This study quantified the annual fossil fuel use in eight user sectors at high spatial resolution using a bottom-up approach. The total fossil fuel use in Fukushima is estimated to have increased by about 91,233 TJ from 2010 to 2015, despite decreases in most socioeconomic indicators. The increase was mainly attributed to changes in electricity generation (104,521 TJ). The three sectors with the greatest decrease in energy use were road transportation (-7159 TJ), industrial and commercial (-3608 TJ), and residential (-2334 TJ). Spatial analysis using high-resolution maps identified areas of increased energy use mainly in central, southeastern, and northeastern Fukushima and confirmed some local variations in energy use by sector. It showed that decreasing energy use in the area within 20 km of the Fukushima Daiichi Nuclear Power Station resulted in increased use in areas located >20 km from the power station. Sensitivity analysis clarified the relations among factors underlying each sector’s changing energy use before and after the GEJE. For instance, consider the electricity generation sector: reduced energy use was caused by decreased energy use intensity (-23,299 TJ) and the increased use of biomass (-4848 TJ), whereas increases were caused by rising utilization efficiency (102,410 TJ) and increased electricity generation capacity (35,988 TJ), which led to a large overall increase for this sector (104,521 TJ). However, road transportation’s negative energy use change (-7159 TJ) arose owing to decreased traffic volumes (-7573 TJ) and decreased energy use intensity (-7177 TJ), despite some positive energy use changes caused by the increased proportion of large vehicles (3684 TJ) and changes in mean travel speed (1381 TJ). The approach used in this study will be helpful for policy makers to evaluate spatio-temporal variations and develop policies to reduce energy use in response to unusual local events.