Fuji, Shizuoka Prefecture 26 October 2016 -- (From the Asahi Shimbun) -- Charcoal from paper mill sludge that once polluted the ocean here southwest of Tokyo could be used to restore contaminated land near the crippled Fukushima No. 1 nuclear power plant.

An experiment in 2011 showed that the charcoal is effective in reducing radioactive substances in soil and preventing the absorption of cesium by plants, said research leader Ai Van Tran.

Tran, 68, a doctor in agricultural science, was conducting the research for the Corelex Group that includes Corelex Shin-ei Mfg. Co., which has the largest share of recycled toilet paper in Japan.

"We would be delighted if our byproduct, which was once a source of environmental pollution, is useful in decontamination. It will also contribute to reducing the waste from papermaking, so it is killing two birds with one stone," said Satoshi Kurosaki, the president of the Corelex Shin-ei.

In making recycled paper, about 30 percent of the raw material remains as sludge. In 2002, the Corelex Group developed "blacklite," a type of activated carbon produced by burning paper sludge. It has a variety of useful properties such as soil conditioning, deodorizing, underfloor humidity control, melting snow and more.

The company produces blacklite from the paper sludge generated at a paper mill in Hokkaido, and it is used at golf courses and farms on the island.

After the radioactive fallout from the accident at the Fukushima No. 1 nuclear plant contaminated a vast area, the team, led by Tran, suggested conducting a trial to use the absorbent property of blacklite to decontaminate the soil.

Between May and October 2011, the company rented about 1,000 square meters of rice fields in Iitate, Fukushima Prefecture. It is one of the most heavily contaminated areas. The team grew rice in soil containing blacklite, and compared the amount of radioactivity in the rice with crops grown on soil with no blacklite.

The result was clear.

The rice harvested from the paddies that contained blacklite had just one-35th of the amount of radioactive cesium that was found in the rice grown on untreated soil. The cesium concentration in the treated soil was about half that in the untreated soil.

Also, the rice in the paddies with blacklite showed much better growth than the other crop.

As the ingredients of blacklite is industrial waste, it only costs about 500 yen ($4.80) for a 30-liter bag.

The enormous amount of soil removed from the surface of the ground in Fukushima Prefecture in the decontamination effort has been bagged and piled up at a temporary storage site. It is waiting to be transferred to an interim storage facility, which is still under construction.

It is expected to take a significant amount of time to process this soil and concerns have been raised over radiation leakage in the meantime.

Tran, who is originally from Vietnam, and his team have acquired the patent for a new method to contain radiation by mixing contaminated soil with blacklite and then sealing it in a tank made of concrete.

It is believed that the soil is gradually decontaminated when an ion exchange process occurs between the mineral in blacklite and the radioactive cesium in the soil.

Tran's paper on his team's experiments attracted attention in the United States, and he has been invited to speak at an international conference on nuclear chemistry scheduled for December in Texas.

The research is still in its early stages, but the Corelex Group has contacted the economy ministry to ask whether blacklite can be used in the decontamination project in Fukushima in the future.