Marubeni Corp. is working on how to jump-start the geothermal industry and tap the heat that powers volcanoes as an alternative to nuclear reactors.

The biggest investor in electricity generation among Japan’s trading houses hopes to draw pools of underground heat with potentially twice the current capacity of geothermal projects operating worldwide.

That would help Japan shift away from atomic reactors that provided 30 percent of the nation’s power before the Fukushima crisis.

“We’ve focused on hydro before,” Masahiro Uegaki, assistant general manager of Marubeni’s domestic power projects, said in an interview at the company’s headquarters in Tokyo. “Recently we are developing solar, wind and other renewable energies. Geothermal is one of our new activities.”

Expanding geothermal power use would benefit turbine makers such as Mitsubishi Heavy Industries Ltd. and Toshiba Corp., both of which already supply equipment outside Japan. Marubeni’s study is possible because the government last year eased rules to allow geothermal projects in protected national parks, part of an effort to boost supplies of renewable energy.

Japan borders the geologically active Ring of Fire, with volcanoes and rift zones that push pools of heat closer to the Earth’s surface. That heat gives the nation potential for an abundant supply of energy that, like nuclear power, doesn’t pollute the atmosphere.

Pressure to develop geothermal energy arises from voter concern about nuclear power following the meltdowns in Fukushima and an ambition to tap the same volcanic heat reserves used in thousands of hot spring spas across Japan.

All but two of the nation’s 50 nuclear reactors remain shut for safety tests because of Fukushima.

More than 70 percent of respondents in an opinion poll by the Asahi Shimbun in February said Japan should scrap nuclear power, a stance favored by environmentalists who note geothermal energy does the same thing as nuclear with much less risk.

“To import a very complex and difficult technology to boil water in the world’s most seismically active country when there is such vast geothermal potential strikes me as madness,” David Suzuki, a Canadian author, environmentalist and board member of the Japan Renewable Energy Foundation, said in an interview.

Marubeni operates a Costa Rican power plant that runs off underground heat and is developing another in Indonesia. It plans to conduct a geothermal survey in the Daisetsuzan National Park in Hokkaido as early as next month, said Uegaki, the power executive at the company.

The study of geological formations will take place in the Shiramizusawa area. Surveyors will work a year before officials decide whether to conduct test drilling.

The next step would be to determine whether the site is suitable for a plant, which usually takes a few years.

Marubeni’s project is among five under consideration at four national parks, according to the Ministry of Economy, Trade and Industry.

Idemitsu Kosan Co., a refiner, plans to conduct a drilling survey in a park in Akita Prefecture this summer.

The projects threaten to revive conflict with hot springs resorts, which are concerned commercial geothermal plants will siphon away the same reserves that they tap. Geothermal developments were largely off-limits before the Great East Japan Earthquake in March 2011 because heat reserves were set aside for the resorts.

“We realize geothermal is one of our energy options,” said Hirokazu Nunoyama, secretary general of the Japan Spa Association. “But there are impacts on the environment. There are cases of hot spring resources running out or thinning, or a drop in water temperatures.”

The association, which has about 1,500 members, submitted a petition to the government last summer opposing “disorderly development” of geothermal power.

Prime Minister Shinzo Abe, since taking office in December, has been rethinking the nation’s energy policies and plans to set out a strategy later this year after the Upper House election in July.

He told lawmakers Feb. 28 that he will restart some nuclear reactors once safety measures are in place. The previous administration aimed to phase out atomic power by the end of the 2030s.

More than 80 percent of Japan’s geothermal reserves are in national parks, according to the Geothermal Research Society of Japan.

Rules set in the 1970s suspended construction of new geothermal power stations inside national parks except for six sites in operation or under construction at the time.

Few geothermal projects were started since the mid-1990s as all the emphasis was placed on atomic and gas-fired power generation. Japan has 539 megawatts of geothermal capacity in operation, about half the output of a typical atomic reactor. Only 4 megawatts of that capacity was added in the last decade, according to data from the government.

Worldwide, about 11,228 megawatts of power come from geothermal projects, according to Bloomberg New Energy Finance. Japan has the potential to produce 23,000 megawatts of power from underground heat, according to the Geothermal Energy Association in Washington. It estimates that only 0.2 percent of Japan’s electricity comes from the technology.

The last commercial geothermal plant in Japan was built in 1999 on Hachijo Island, about 287 km south of Tokyo. It is operated by Tokyo Electric Power Co.

Japan has 17 geothermal plants currently in operation, according to data compiled by government-affiliated Japan Oil, Gas and Metals National Corp.

To encourage use of renewable energy, the government has been offering incentives through feed-in tariffs since July. Geothermal is ¥27.3 per kwh for plants with capacity of 15,000 kw or larger, and ¥42 for smaller plants, both for 15 years.

“Geothermal plants are rapidly increasing in major geothermal countries abroad, and we are the only country that is not moving ahead,” Susumu Tanaka, chairman of the Japan Geothermal Association, said in a statement on the group’s website.