|Combustible: Firefighters last month tackle a debris fire in Natori, Miyagi Prefecture, likely caused by spontaneous heating. KYODO|
Spontaneous debris fires add to Tohoku woes
SENDAI — Smoke and a burning smell filled the air in central Sendai Sept. 16.
It was caused by a fire more than 10 km away at a debris storage site in Natori, Miyagi Prefecture, that burned for more than five days.
Tons of debris from the March 11 disasters are spontaneously catching fire at storage sites in the Tohoku region, adding to the headaches of local authorities.
Miyagi Prefecture says it alone has had 15 such blazes.
In late August, a storage site near a fishing port in Kesennuma caught fire, burning about 25,000 cu. meters of debris. Although most of the sites are far away from residential areas, locals have been voicing strong concerns.
According to the National Institute for Environmental Studies, when flammable waste, including wood chips and tatami, is piled high or compressed with heavy machinery, microbes generate methane gas.
The waste material is heated by chemical oxidation and biological decomposition, and catches fire as it comes in contact with a methane gas pocket.
The phenomenon is known as spontaneous combustion.
To avoid such fires, experts say waste should be piled no higher than 5 meters, individual piles kept to 200 sq. meters or less and separated by others by 2 meters or more of open space.
As of Sept. 21, debris stored at temporary sites in Iwate, Miyagi and Fukushima prefectures amounted to 12.74 million tons, a level approaching the roughly 14 million tons collected after the Great Hanshin Earthquake in 1995. The Tohoku total is expected to rise to about 22.72 million tons.
In the case of Miyagi Prefecture, there is a scarcity of flat land in the ravaged hit coastal area suited to storing debris.
A separate site to compact and incinerate the debris won’t be ready until early next year, while debris at the current sites continues to pile up day by day.
Ishinomaki, where six fires have occurred since April, has started gathering tatami mats, which are likely to emit methane when they rot, at a single location. City officials started patrolling the area and installed pipes to send air into the debris piles.
“It’s hard to see if its steam or smoke rising from the piles of debris,” a city official said. “I want the prefecture to start the disposal of the debris as soon as possible.”