Industries
Explosion protection in biogas and wastewater treatment plants
Biogas plants and wastewater treatment works produce methane, which makes them explosion-prone. H₂S also forms, which is both flammable and toxic. An explosive atmosphere develops in the digesters, the gas holders, the gas pipework and around the gas engines. These are often smaller municipal or agricultural installations without an Ex specialist of their own, so clean documentation counts for a great deal here. The documentation has to keep the gas zones, the whole gas path and the confined spaces current.
Industry experience
Sound familiar?
A digester or gas holder is extended, but the zone classification does not follow the change.
Around the gas engine (CHP unit) it is not clear how far the methane zone extends.
H₂S is treated as a toxic gas, but the classification does not take account of it being flammable.
People enter a tank or a chamber for maintenance, but the documentation does not record the risk of gas accumulating.
Ahead of an audit you spend days gathering the zone drawings, the equipment list and the inspection certificates.
If any of this sounds familiar, what you need is not another document but software that lives alongside the whole gas path and its changes.
Hazards
Typical explosion hazards in biogas and wastewater plants
The industry deals with gas hazards, and alongside the main flammable component there is a toxic gas present as well:
| Hazard source | Where typical | Typical zone |
|---|---|---|
| Methane / biogas (IIA) | digesters, gas holders, gas pipework, gas engine | gas zone (0/1/2) |
| Hydrogen sulphide (H₂S) | digesters, sewers, gas treatment, condensate traps | gas zone (1/2), toxic as well |
| Gas accumulating in confined spaces | tanks, chambers, wet wells, sewers | gas zone, critical on entry |
| Hot surfaces and electrostatic charging | gas engine, hot work, maintenance | an ignition source in every zone |
Methane falls into gas group IIA and is present throughout one continuous, closed gas path, from the digester through the gas holder and the gas engine to the flare. H₂S is not only toxic and corrosive but flammable too, so the classification has to address its explosion risk as well. Confined spaces — tanks, chambers, wet wells, sewers — accumulate gas, which makes entry and maintenance a particular risk. Since these plants often operate without an Ex specialist of their own, current documentation is worth even more here.
When we help
Typical situations when it’s worth talking
Flammable and toxic at once: methane and H₂S
What distinguishes biogas and wastewater plants is that explosion protection and the toxic-gas risk have to be managed together, along one connected gas path:
Methane presents the explosion hazard. Gas group IIA; it forms an explosive atmosphere inside the digesters, gas holders and gas pipework.
H₂S is both flammable and toxic. The classification has to address the explosion hazard as well, not only the toxic risk.
The gas path is one continuous system. From the digester through the gas holder and the gas engine to the flare, the zones are connected, so one change affects several points.
Confined spaces are most dangerous on entry. Because gas accumulates in tanks, chambers and sewers, maintenance and entry present a particular risk.
The solution
How EPDS helps in the biogas and wastewater industry
EPDS brings explosion protection documentation into one system, from the digester to the gas engine:
Zone and equipment register in one place.
EPDS records the zones of the digesters, gas holders, gas engines and pipework, and every Ex device, in one searchable place.
The whole gas path in one system.
The software handles the zones as one connected whole, from digester to flare, so the effect of a change can be traced along it.
Management of change.
The software traces the effect of an extension or new equipment through the zones and the protective measures.
No more overdue inspections.
The system gives notice of inspections as they fall due, and records the ones completed.
An audit-ready report in one click.
EPDS assembles the report of zones, equipment and inspections, per site too.
Documentation that is always current.
You can look back at any time to see who changed what, and when.
Knowledge hub
Before you decide, get informed.
Our expert knowledge base explains the concepts of explosion protection clearly.
FAQ
Frequently asked questions
Which gas group do methane and biogas fall into?
Methane falls into gas group IIA and temperature class T1. The main flammable component of biogas is methane, so equipment has to be specified for that, while also taking the presence of H₂S into account.
Is H₂S flammable or toxic?
Both. Hydrogen sulphide is toxic and corrosive, but it is also flammable, so the explosion protection classification has to address its explosion risk as well, not only the toxic one.
Why is entering a tank or a chamber dangerous?
Gas can accumulate in confined spaces, presenting a risk of both explosion and poisoning. Entry and maintenance are therefore a particular risk, and the documentation has to record it.
When does the zone classification have to be redone?
At every change that affects the explosion hazard: extending a digester or gas holder, a new gas engine, or a modification to the gas treatment or the process. In EPDS this is part of management of change.
Does a biogas plant or wastewater treatment works need explosion protection documentation?
Yes. Wherever a flammable gas can create an explosive atmosphere, the documentation is mandatory under decree 3/2003. (III. 11.), and it has to be kept current.
Let’s talk it through — free consultation
In a short, free conversation we show you the EPDS system mapped onto your processes, and review where your documentation stands today.