CSB: Preliminary Evidence Points to Combustible Dust in Nebraska Plant Explosion
A fatal explosion at a biofuels facility in Fremont, Nebraska, on July 29 may have followed “a large release of combustible wood product, most likely wood dust from the process,” according to an investigation update published last month by the Chemical Safety and Hazard Investigation Board (CSB). The incident killed an operator who worked at Horizon Biofuels and his two daughters, who were 8 and 12 years old. At the time the update was published, CSB had not been able to approach or enter the facility due to combustible material continuing to smolder and the potential for the building to collapse. But the agency says it is continuing to investigate the cause of the initial dispersion of dust and conditions at Horizon Biofuels prior to the incident.
The Horizon Biofuels facility produced wood pellets for home heating fuel and wood mulch for animal bedding. According to CSB’s update, the facility was an adapted grain mill and had a dust collection system intended to help control wood dust generated from its production processes.
“Air blowers carried the wood dust and routed it through an enclosed system into the dust control equipment,” the agency explains. “The dust control equipment, located on the top floor of the tower, separated the wood dust from the carrier air and discharged the clean air outside the building.”
Video of the incident first shows what CSB describes as “a large puff of dust or smoke” coming from windows near the top of the tower, then flames jetting out of the windows, and finally “a large explosion at the top of the tower.”
CSB’s investigation of the incident is ongoing. The agency plans to examine the facility’s dust handling and control systems; interview workers, management, first responders, and others about Horizon Biofuels’ operations, maintenance, and safety practices; and investigate whether previous audits or inspections addressed combustible dust hazards within the facility.
To learn more, read CSB’s news release and its investigation update (PDF).