TOKYO -- Two fires broke out in Fukushima Prefecture at temporary collection sites for disaster waste generated by flooding of houses due to Typhoon Hagibis, which lashed eastern Japan in mid-October, prompting experts to urge caution against similar possible incidents.
In both fires in the northeastern Japan prefecture, it is believed that hazardous material among the disaster waste caught fire. As blazes of a different kind also took place several months after disaster waste was generated in the past, one expert warned, "It is necessary to be on the alert against possible fires even several months after a disaster hit."
One of the two Fukushima Prefecture fires occurred at a temporary collection site for disaster refuse in the prefectural city of Motomiya on the morning of Oct. 17, five days after Typhoon Hagibis made landfall in parts of eastern Japan. After the fire broke out at a site for collecting household appliances, it consumed a total of approximately 4 square meters.
The Ministry of the Environment issued a warning against similar potential blazes the following day. In spite of this, another fire started in a pile of flammable trash at a temporary waste collection site in the prefectural city of Sukagawa on the evening of Oct. 20.
"There is a possibility that hazardous material left among flammable garbage ignited," said Toshiaki Yanai, head of the city government's environment division.
Apart from these common flames, there are fires caused by heat accumulation several months after a disaster. Kazuto Endo, a senior official at the Fukushima branch of the National Institute for Environmental Studies, said, "In areas affected by the Great East Japan Earthquake and tsunamis (in 2011), there were at least 30 fires caused by a buildup of heat."
In the wake of the 2011 disaster, a total of some 31 million metric tons of disaster waste was generated. As there were not enough land lots for temporarily storing the litter, piles of waste soared high in affected regions. In the hardest-hit prefectures of Fukushima, Iwate and Miyagi, a total of 38 fires occurred due to heat accumulation between May 2011 and June 2013.
According to guidelines compiled by a group of experts including Endo immediately after the 2011 quake disaster and other sources, heat accumulation fires are triggered by the following mechanisms:
-- Combustible trash put out in the early period of waste collection generates heat as microbes using oxygen actively move around it.
-- When the waste is further piled up, it gets compressed by the weight of the trash and heavy machinery such as shovel loaders operated on mountains of rubbish, preventing the heat from being released outside.
-- When the piles of garbage soar more than 5 meters high, the speed of heat generation inside the trash overtakes that of the heat released from the surface of the piles, accelerating heat accumulation.
-- When a pile of waste stores heat with temperatures of over 80-90 degrees Celsius, oils contained in plants and trees get oxidized and produce heat.
-- The higher the temperatures rise, the faster those oils get oxidized and generate heat, eventually catching fire spontaneously.
The guidelines call for keeping a pile of burnable trash no more than 5 meters high and each mountain of waste no more than 200 square meters as part of measures to prevent heat accumulation blazes. The guidelines also urge authorities to maintain the height of perishable trash such as tatami mats at a maximum of 2 meters and allow it to reach no more than 100 square meters in size.
Endo has patrolled areas affected by Typhoon Hagibis and noted, "Some local bodies that had not previously experienced major flooding damage are leaving disaster waste piling up high." He has thus given guidance to those municipalities to keep their mountains of rubbish lower.
(Japanese original by Takashi Yamashita, Integrated Digital News Center)