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Anaerobic Digester/ Biogas plant explosions tragic update

Anaerobic Digester Plant Explosions – Explosive Risk at Biogas Facilities

Any anaerobic digester plant explosion is one too many. Read on to discover a number of incidents that have shown the explosive potential of methane in AD plants can be unleashed when least expected.

Nobody was hurt in the biogas digester plant explosions reported in the media in the UK until 2020. In December 2020, that changed with four tragic deaths in the UK in one incident.

Now again, in September 2023, we have updated this article to include two explosions in as many months. The most recent anaerobic digestion plant explosions happened at two biogas facilities, one near Nottingham and the other in Oxfordshire.


The following news serves to emphasize that very real risks exist in anaerobic digestion and biogas production:

Facts to Remember About Anaerobic Digester Plant Explosions

A little bit of gas in the air will burn and not explode, equally a methane-filled space containing no oxygen will not explode, rather it will put out a flame.

But, between these concentrations, there is the danger of an explosive zone. An explosion can easily cause death.

In Europe a set of regulations known as the ATEX Regs. applies to assess and manage explosion risks of this sort.

In the UK the ATEX Regs. are applied under the Dangerous Substances and Explosive Atmospheres (DSEA) Regulations*. In addition, most site owners/ operators should also be applying the COMAH regulations. All biogas plants must comply with those regulations. (* Equivalent Regs apply in Scotland, Northern Ireland, and Ireland)

Anaerobic Digester/ Biogas plant explosions tragic update

Updated October 2023:

STOP PRESS – October 3, 2023:

Lightning Strike Sparks Biogas Tank Explosion and Fire at Oxfordshire Recycling Plant

Incident Overview

An unexpected lightning strike at the Severn Trent Green Power Plant in Cassington, Oxfordshire resulted in a massive explosion on 2nd October 2023. The blast was caused by the ignition of biogas in the gas collection domes above the tanks, leading to an enormous fireball visible from afar. Fortunately, no injuries were reported despite this dramatic event.

Immediate Impact and Emergency Response

Severn Trent Green Power has worked closely with emergency services to secure the site and address any issues following an explosion that caused widespread power outages across several communities including Witney, Burford, Chipping Norton and Milton under Wychwood. The company is committed to resolving this situation as quickly as possible while ensuring safety remains a top priority for all involved parties.

Safety Measures and Local Advisories

Thames Valley Police issued a statement following the explosion that no injuries had occurred and precautionary measures were being taken. The A40 was closed between Wolvercote and Eynsham while residents were advised to stay indoors with windows and doors shut tightly.

A number of reports suggest that no lightning rods had been installed that if present may have diverted the strike directly conducting the thunderbolt and safely earthing it into the ground.

The anaerobic digestion facility processes source-separated food waste and there would have been procedures in place to guard against such an event through the application of the UK's ATEX and DSEAR Regulations, and in addition, a COMAH assessment would have been undertaken.

Biogas – The Risks and Benefits

The Cassington plant explosion has highlighted the dangers associated with biogas, a renewable energy source derived from decomposing organic waste. While typically safe it serves as an important reminder that robust safety protocols are necessary for preventing accidents like this one in future.

Severn Trent Green Power has emphasized its dedication to safety following the explosion by working alongside emergency services in managing and mitigating its effects. They continue to prioritize this commitment as they move forward.

Uk Update on Anaerobic Digester Plant Explosions – Conclusion

The Oxfordshire recycling plant explosion highlights the significance of emergency preparedness in renewable energy operations. Thankfully due to efficient response measures and existing safety protocols, no injuries resulted from this unexpected lightning strike. The incident serves as a reminder for all those involved with green power generation about the importance of being ready at all times.

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December 2020 Update:

Avonmouth explosion: Investigation after four killed in blast

A tragic accident occurred at a wastewater treatment works on 4 December 2020 at a Wessex Water sewage sludge treatment facility near Avonmouth.

Investigations are continuing into what caused an explosion at a wastewater treatment works that killed four people.

[Permission to use the BBC image of the damaged biogas digester tank has been requested.]

Three employees of Wessex Water and a contractor were killed in the blast at a water recycling centre in Kings Weston Lane, Avonmouth, on Thursday.

Graphic shows that Explosion risk assessment is importation to reduce the risk of an anaerobic digester plant explosion.This news is particularly distressing given that for more than 15 years now the DSEA Regulations have been in force. The risks are well-known and the regulations should, if correctly applied and enforced by the HSE, ensure that all those operating any facility of this type carry out a formal risk assessment (RA).

Once the RA has been done, procedures must be put in place and responsible staff allocated the duty of ensuring that only those people fully informed and trained in these risks are allowed to gain access to the Risk Assessed areas.

The BBC Anaerobic Digester Plant Explosions News article can be viewed here.

 Anaerobic Digester Plant Explosions May 2020 Update: There have been some notable biomass digester explosions recently in the US, which we have updated this page to cover. In the case of the first, it is not clear what caused the explosion, and whether the incident involved methane gas in some way, this being the number one cause of anaerobic digestion plant explosions.

Maine Paper Mill is back in business after dramatic pulp digester explosion

JAY, Maine (AP) 23 April 2020 — A paper mill disabled by a dramatic explosion caught on video last week has resumed production with two of its three paper machines, officials said Thursday.

The restart of Pixelle Specialty Solutions' Androscoggin Mill in Jay followed a blast that happened in a large, kettle-like digester in which a slurry of wood chips, water, and chemicals is transformed into pulp. An assessment of what caused the rupture continues.

The two paper machines, which restarted Wednesday, are using pulp produced at other Pixelle mills in Ohio and Pennsylvania, and supplemented by purchases from others, the company said.

The Spring Grove, Pennsylvania-based company is assessing options for long-term pulp production at the plant.

Tim Hess, Pixelle's president, and CEO said Thursday he was thankful that no one was hurt and that there was no environmental damage. Workers managed to safely shut down the mill to prevent further damage, he said. via apnews.com

Major Gas Explosion Injures Two at Nottingham AD Plant

September 2017:

A significant gas explosion has left two individuals seriously injured at an anaerobic digestion (AD) plant in Nottinghamshire, UK. The incident unfolded at Bio Dynamic, a facility that specializes in converting food waste into renewable energy and fertilizers.

Collapse of a gas tanker

According to reports, the explosion occurred at the Colwick Industrial Estate in Nottingham, with witnesses describing the collapse of a gas tanker and a 30-foot gas tank lying across the road. The emergency response was swift, with paramedics from the Hazardous Area Response Team providing critical care to the injured individuals.

Food Waste Processing Facility Explosion Incident

Bio Dynamic processes around 50,000 cubic meters of food waste annually, including expired food from retail and hospitality businesses, as well as organic waste from food processing plants. The East Midlands Biogas Centre plays a crucial role in converting this waste into energy, powering the plant's Combined Heat and power (CHP) units with the produced biogas.

While the investigation is ongoing, authorities have ruled out terrorism as a potential cause for the explosion. Both the Nottinghamshire Police and Nottinghamshire Fire and Rescue are actively involved in determining the exact circumstances of the incident.

Bio Dynamic has not yet issued an official statement regarding the explosion.

This incident underscores the importance of safety measures and protocols in waste-to-energy operations, and it serves as a reminder of the potential risks associated with such processes.

Tags: Anaerobic Digester Plant Explosions, Nottingham, Gas Explosion, AD Plant, Bio Dynamic, Hazardous Area Response Team, Renewable Energy, Safety Measures

The cause of the above Anaerobic Digester Plant Explosion will not be known until investigations have been completed. But a UK Anaerobic Digestion Plant (so-called) explosion has already been reported at the following UK agricultural university:

Harper Adams Anaerobic Digester Plant Explosion

JUNE 2014: An eco-friendly power station suddenly exploded this morning showering the surrounding area with hundreds of tonnes of stinking cow dung.

The blowout in a slurry processing tank happened in the early hours at the plant outside Harper Adams University near Newport in Shropshire.

Onlookers said one side of the 30-foot-tall corrugated metal building was completely torn off while the roof and supporting wall collapsed.

Thousands of gallons of slurry spilled into a nearby farm flooding one road and leaving several fields waterlogged.

Fire crews and police arrived at the scene at 10 a.m. and sealed off the scene with tape while the buildings were inspected.

Environment Agency officials spent the day at the site assessing the damage and working to minimise the effect on the environment. via www.dailymail.co.uk

Again, thankfully, nobody was injured, and the author of this article believes that this was not correctly described as an explosion. It was an implosion caused by a pump system operational error.

Digester Explosion Pensacola

As International Paper's Cantonment mill resumed full operations this week, the company has released more details about the 22 January 2017 explosion.

Spokeswoman Janice Holmes said Tuesday that the mill experienced a power failure the day before the explosion because of an electrical fault in the power distribution system. The power failure forced the mill out of operation, which caused gas to build up in an on-site pulp digester. That is what officials believe ultimately caused the explosion.

The company's preliminary findings released on March 9 show that when the digester was out of operation for an extended period of time, the gases built up and created an “explosive atmosphere.” Again, there were not any employee injuries at this Anaerobic Digester Plant Explosion. via www.northescambia.com (Kamyr digester explosion)

Explanation of the following very unusual biogas digester explosion:

The membrane referred to below is “EPDM” (ethylene propylene diene monomer (M-class) rubber), is the extremely durable synthetic rubber roofing membrane which is used to cover biogas tanks.

Now having given you the background, our extract from the article about this anaerobic digestion plant explosion follows:

EPDM Failure Causes Anaerobic Digester Explosion

(March 2013) The chances of an anaerobic digester exploding are slim to none. But that's exactly what happened at Tim Bielenberg's Oak Lea Farm in Aumsville, Ore. via www.tpomag.com

“The gas that was in that head-space combusted rather than going down the gas train to the engine or any other location. During that process, you have to have the exact combination of ambient air and methane for it to be combustible. It came in contact with some ignition source.”

“Fortunately, the system operated as designed so it began to shut itself down after the dramatic change in gas pressure and flame arrestors on the biogas train also proved effective.”

The minor damage was only above the rim of both tanks, and no one was hurt in this anaerobic digester plant explosion. While the chances of this happening again are rare, RES has taken steps to prevent any recurrence.

“There are tremendous ground fields around the engine and the interconnection,”

says Tank.

“We ground the tanks, and we now apply a ground application to the EPDM as well.”

Graphic shows that Explosion risk assessment is importation to reduce the risk of an anaerobic digester plant explosion.
Click on the image above and request a quote for an AD Facility Explosion Risk Assessment Now!

The risks at biogas facilities include, for example:

  • Fire and explosion
  • Confined space hazards
  • Risk of Asphyxiation Risk of gas poisoning (H2S, NH3)
  • Risk of high-pressure gas or liquid leaks
  • Risks associated with rotating mechanical equipment Risks associated with pathogens (diseases)
Our Opinion

Plastic membrane covers are normally safe as they tend to deflate in the event of a small gas leak. In addition, they don't provide a rigid void with part air and part methane present, which is of course much more likely to become an explosive mixture of methane and air within, what are called “the explosive limits!”

Risks and safety measures for anaerobic digestion: How can you make your plant safer?

All UK AD Plants should have completed an ATEX Risk Assessment of their specific site explosion hazards and taken action to ensure that their AD facility meets all legal UK requirements. Similar requirements may exist outside the UK – Check this with your regulatory authorities.

Other Notable AD Plant Explosions

Anaerobic Digestion Plant Explosion Caught on Film

A US Digester Plant Explosion Took Place Back in 1987

On February 6, 1987, two workers at a wastewater treatment plant were re-draining a sewage digester when an explosion lifted the 30-ton floating cover, killing both workers instantly. via www.cdc.gov

Sewage Biogas Plant Biogas Explosion in Madison US in 2016

The day of October 16, 2016, in Madison, Wisconsin began with thunder and lightning. As the employees of Madison Metropolitan Sewerage District arrived at work, lightning struck the fibreglass enclosure of their pressure regulator and flame-arrestor on top of the digester. A fire was sparked and quickly grew with heat intense enough to melt the lead weights in the pressure regulator. This whole time the digester was operating and generating highly flammable methane gas.

Employees were evacuating the area as the fire was extinguished, but the big event they were all bracing for never happened. There was no explosion! So many anaerobic treatment facilities have had explosions in nearly the same situation.

Fires and explosions associated with anaerobic digesters and methane storage systems are more common than people realize, mostly because of widespread under-reporting. This is especially true in “near miss” situations, where there is no human injury or death. via teamaquafix.com

Explosion and Fire at the Southwest Wastewater Treatment Plant in Springfield, MO, US

Two contract workers were injured after an explosion and fire Monday at the Southwest Wastewater Treatment Plant in Springfield, MO, the Springfield Fire Department said in a release. Fire crews responded to the municipal facility at about 4 p.m. Describing the incident as a “low order explosion with flash fire,” officials said a digester tank at the facility received damages and partially collapsed.

A group of three contractors were reportedly performing work on the digester tank at the city-owned facility when the explosion and fire occurred.

“They were working on the roof of this digester that had been emptied out,” Springfield Fire Battalion Chief, Heith Aldridge, told the Springfield News-Leader. “Apparently, there was a pocket of methane gas that was enough that, while they were working, it caught fire.”

The blast prompted the workers to jump from the top of the 15-ft tank. Two of the contractors received non-life-threatening injuries and were transported to an area hospital for treatment. via www.powderbulksolids.com

European Anaerobic Digestion Biogas Accidents

In Europe, there were about 800 accidents in biogas plants between 2005 and 2015. Fortunately, less than a dozen of them had consequences for humans. Here are some examples.

In 2018, an explosion followed by a fire occurred at the level of the gasometer in the post-digestor of the farm plant in Saint-Fargeau, France. The accident happened during the initial test for the operation of the agitator when its propeller was replaced.

In 2005, a large quantity of H2S leaked in the charging hall of the biogas plant in Rhadereistedt, Germany. The workers don’t follow the procedure to discharge the truck because of a breakdown of the lid covering the tank. The tank containing animal and dairy waste is left open. via www.biogasworld.com

Conclusions for Anaerobic Digester Plant Explosions

Biogas risks include explosion, asphyxiation, and also on occasion disease, and hydrogen sulfide poisoning.

Extreme caution is necessary when working with biogas. Adequate ventilation, appropriate precautions, good work practices, engineering controls, and adequate personal protective equipment will minimize the dangers associated with biogas.

Wherever possible, digester-associated tasks and maintenance should be performed without anyone having to enter confined spaces, including pits.

Systems should be initially designed so that confined space entry is not required to perform maintenance. via farm-energy.extension.org

Above all the UK DSEA Regulations require a Risk Assessment to be undertaken for all facilities where a risk of explosion is possible. Biogas Plant Owners and Operators are not operating legally unless they apply the DSEA Regulations. Similar regulations apply to the other UK nations and throughout the EU, under the ATEX Directives.

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    • FirstGuy
    • December 30, 2017

    I see you do report negative news about Anaerobic Digestion sometimes, but your blog would be more balanced if you didn’t keep quiet about major safety problems like this one:

    “A health and safety investigation is under way after two people received “serious injuries” after an explosion at a biogas plant.

    Nottinghamshire Police confirmed it had received reports of a gas explosion”.

    Your readers should be told.

    1. Reply

      FirstGuy – You say “major safety problems like this one”. Sorry, don’t agree, this was a minor incident. It was not what should be considered as a major safety problem, in my opinion.

    • James
    • February 10, 2018

    These big covers full of gas… Reminds me of WW2 airships. Where are those now? Is this a safe way to store flammable gas.

  1. Reply

    I have checked out your site and i have found some interesting, and original content. maybe I am new to this, but What is “EPDM Failure”. How about explaining your use of these things sometimes for the guys who are learning.

      • radimin
      • March 15, 2018

      Bailey Davis: Sorry! “EPDM is the extremely durable synthetic rubber roofing membrane used to cover biogas tanks.” I’ll explain that in the article as well.

    • Rayford Jones
    • May 18, 2018

    This is gas! Bad things gonna happen unless you take great care. Yep – even explosions. Liking your website mate!

    • karina outleader
    • August 10, 2018

    To me this shows how risky anaerobic biodigesters can be if something goes wrong. Bad enough that a farm family is endangered and possibly injured, but at least farmers can site those hazardous digesters well away from their homes and barns. The worst part is that in cities, such digesters are put close to homes. it’s not right to do this without sufficient buffer zones. If something bad happens, it also will likely impact on the nearest neighbors. See this video https://www.youtube.com/watch?v=7LPfno2KPcg

    • F Pope
    • August 15, 2018

    Hello. Bad things can happen. Take care.

    • BobbieBad
    • December 4, 2018

    just be careful. the biogas does not explode. i like this biogas is the future in addition to hho houses nowdays do not require to be connected to the grid all of us need to do this and enjoy the greedy goverments and oil business passing away, an energy transformation is coming soon.

    • Waldo Connor
    • February 19, 2019

    Hello. I have checked your anaerobic-digestion.com and this is the only reference to an Anaerobic Digester Plant Explosion. Where can I find someone to do an explosion risk assessment for an AD Plant?

      • radimin
      • February 27, 2021

      We work with a consultant who does these all the time. Use our Contact Form to make a request and we will give you a quote.

    • Gus
    • June 6, 2019

    Hello Waldo. Try GC Safety Services as they cover Fire and Explosion risk assessment at such sites

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