There is a prefectural central purification center in Shimono, Tochigi Prefecture. Shimotsuke has 24119 households and a population of 60081. The prefectural central purification center extracts hydrogen from methane gas generated in the process of treating sewage sludge and uses it for power generation.

Japan's population is approximately 124.88 million, which is about 2,100 times the population of Shimotsuke City, Tochigi Prefecture, so a simple calculation shows that Japan's annual electricity generation is 5.2 billion kWh.

The electricity generated is sold to the power network.

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"Status of development of digester gas power generation facilities, etc."

https://www.pref.tochigi.lg.jp/h14/shoukagasu_seibijyoukyou.html