Concern about climate change has led to a global shift away from using carbon-emitting coal for electricity, but in post-Fukushima Japan, where nuclear remains a dirty word, coal has become king.

When it accepted the Paris Climate Accord in late 2016, Japan — the world's fifth-largest emitter of greenhouse gases — pledged that no effort would be spared in fighting climate change. The government committed to a 26 percent reduction in emissions by fiscal 2030.

But the reduction was viewed as insufficient by environmental activists, as it only represents an 18 percent cut when compared with levels under the 1997 Kyoto Protocol's base year of 1990.