CSB investigating fatal Horizon Biofuels explosion

The U.S. Chemical Safety and Hazard Investigation Board (CSB) recently announced it has launched a formal investigation into the fatal explosion and fire at the Horizon Biofuels facility in Fremont, Nebraska that occurred July 29.

The CSB announced Aug. 1 it had sent a team to investigate the explosion. The U.S. Occupational Health & Safety Administration (OSHA) is also investigating, according to local news station WOWT.

The accident site is approximately 30 miles northwest of Omaha, Nebraska. The blast killed three people who were in the facility at the time of the incident.

“This horrific incident should never have happened. We want to prevent a terrible tragedy like this from occurring again,” said Steve Owens, CSB chairperson. “The CSB is deploying a team of investigators who will work to determine the root cause of this horrific incident and identify actions to help prevent a tragedy like this from happening again in the future.”

Combustible dust ruled potential cause

According to local media reports from the Fremont Tribune and WOWT, the Nebraska State Fire Marshal’s office said in a July 31 release the agency’s preliminary investigation found an accidental dust explosion led to the incident.

“A preliminary investigation indicates an accidental dust explosion occurred during the manufacturing process. Additional investigation efforts are currently impeded due to the instability of the structure.”

—Nebraska Fire Marshal Agency

The CSB said it has investigated a number of serious combustible dust incidents over the years and has issued numerous safety materials on the dangers of combustible dust, including videos, alerts, and a major hazard study.

The facility was cited by OSHA in 2012 and again by the Nebraska Department of Environment and Energy (NDEE) in 2025 for issues with combustible dust buildup and escape.

Several news outlets have mentioned biomass self ignition as a potential danger when handling wood pellets. Preliminary evidence pointed to a combustible wood dust explosion.

Two children were waiting for their father to finish work

CBS reported the bodies of all three victims were recovered the night of July 30. Fremont Mayor Joey Spellerberg identified Dylan D. Danielson, 32, of Columbus, Neb. as an employee of the business during a news conference.

The Tribune reported Fayeah Danielson, 8, and Hayven Danielson, 12, half-sisters and Dylan Danielson’s children, were in the building during the blast just before noon. Spellerberg said the girls were waiting for their father to finish work because they were going to a doctor’s appointment.

Horizon Biofuels occupied formerly vacant feed mill

Horizon Biofuels, Inc. was formed in 2006 by a group of Midwest business people to manufacture renewable energy and products from locally grown and recycled feedstocks, according to Zoominfo. The company’s first operation was commercially producing biodiesel from recycled cooking oil and animal fat in the village of Arlington, Neb., a few miles east of Fremont.

In 2007, Horizon purchased the vacant Golden Sun Feeds mill in Fremont and began converting it into a fuel pellet mill. Before the explosion, operations at the facility converted wood waste destined for landfills into fuel pellets for domestic and industrial use, along with animal bedding through subsidiary Elkhorn Valley Bedding.

Horizon was regularly awarded grants from the Nebraska Department of Environmental Quality (NDEQ) for waste reduction and recycling, including:

• In 2009, NDEQ awarded $34,407 to purchase equipment for biopellet fuel production from sources such as waste wood, cardboard, newspaper, and storm debris. The equipment included a pellet mill, forklift, stretch wrap machine, and a spark detection & fire suppression system.
• In 2010, NDEQ awarded $94,715 to purchase a portable horizontal grinder to grind over-sized wood pallets, and to purchase six roll-off containers used to transport and store the materials.
• In 2018, NDEQ awarded $170,000 for 50% of the cost of industrial wood shredding equipment to shred mixed wood waste - including shipping pallets, crates, and construction waste - to remove metal and other contaminants.
• In 2021, NDEQ awarded $23,618 for 50% of the cost to purchase 10 roll-off containers to expand collect sites and store 2,000 - 3,000 tons of wood waste.

OSHA and NDEE citations, previous fire damage

The Tribune reported a history of incidents at the Fremont facility.

In 2012, a complaint to OSHA prompted an inspection of the business. OSHA cited Horizon with $12,000 in penalties for four serious violations and one other violation:

• Lockout-tagout
  • Standard: 29 CFR 1910.147(c)(1)
  • $3,000 penalty
  • Horizon did not establish an energy control procedure - also known as a lockout/tagout procedure - nor train its employees on that procedure, to prevent equipment from unexpectedly energizing or releasing energy during maintenance.
• Forklift training
  • Standard: 29 CFR 1910.178(l)(2)(ii)
  • $3,000 penalty
  • Horizon did not provide classroom training, practical training, or evaluations to its employees on how to operate the facility’s forklift.
• Dust accumulation
  • Standard: 29 CFR 1910.213(s)(6)
  • $4,200 penalty
  • Horizon failed to prevent wood dust accumulation in the mill and basement areas sufficiently to prevent fire hazards.
• Hazardous chemical handling
  • Standard: 29 CFR 1910.1200(e)(1) and 29 CFR 1910.1200(h)(1)
  • $1,800 penalty
  • Horizon did not develop a written program or training to communicate the potential hazards of a high-temperature grease used for preventative maintenance.
• Respirators
  • Standard: 29 CFR 1910.134(c)(2)(i)
  • $0 penalty
  • Horizon did not provide employees information about proper care and use of respirators.

The initial penalty issued in Feb. 2012 was reduced by half and settled informally. The case was closed in June 2013.

In May 2014, a wood wall in the building’s grain elevator caught fire, which damaged electrical conduits. The fire spanned from the basement up into the legs of the elevator.

Local news station Dakota News Now reported the NDEE investigated an air quality complaint at Horizon Feb. 11, 2025. NDEE identified wood dust beyond the property line and instructed Horizon to conduct an inspection and perform maintenance of its baghouse and production equipment.