SAFETY OF BIOGAS PLANTS

These are just basic training slides, may vary from standards

History of Biogas Safety Incidents

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1. leakage in the storage tank and / or on the distribution network of the biogas,

2. Accidental release of H2S especially in mixtures of septic waste,

3. Water pollution caused by effluent discharge,4. Presence of dangerous products in the raw material

used to produce biogas, 5. Overflow, freezing of valves, high pressure inside

the digester,

BIOGAS DIGESTER SYSTEM CONCERNS

Releases Nitrogen and ammonia into the atmosphere both of which

hazardous

Can release Hydrogen Sulfide a very toxic gas

Methane released can create explosive atmosphere

Stored raw materials get into water supply can contaminate the

water

Transportation is of a concern because methane is explosive

although new technology may allow it to be stored in powder form

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SAFETY HAZARDS

We can find some risks in a biogas plant such as

Fire and explosion

Toxicity and poisoning

microbiological risks.

Other risks

The construction of a biogas plant and its maintenanceshould be well monitored in order to manage risks.Prevention of people from being expose to those risks andchecking of all materials (including corrosion) should berealized with the aim of making the production of biogassafer.

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Fire and Explosion

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Fire and Explosion

Biogas plants process large quantities of combustible andtoxic gases, which pose increased fire and explosionhazards in case of faults in design, materialor control.

Methane is highly flammable and forms explosive mixturesin combination with the oxygen inthe air.

Therefore explosion protection is very important in biogasplants. For these reasons biogasmust be prevented fromentering working areas.

Specific safety measures must be guaranteed duringconstruction and operation of biogas plants. The risk ofexplosion is particularly high close to digesters andgasholders (overpressure safety devices).

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Fire and Explosion

safety precautions should prevent any naked flame beingintroduced into the tank; furthermore methane is explosiveif mixed with air in proportions ranging from 5%. to 1% byvolume.

Do not allow smoking near biogas plant as well as nearutilization points. (No Smoking Zone).

Check the pressure gauge regularly. If pressure increasesfrom 2 PSI, quickly use or evacuate some gas in air to savethe explosion in the plant.

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Toxicity and PoisoningThe second major risk is toxicity related to the leak of H2S, because

this gas is very toxic and we know that this gas is one of the mostabundantly produced in anaerobic digestion.

If biogas is inhaled in sufficiently high concentration, it canresult in poisoning or asphyxiation symptoms and even death.Especially the presence of hydrogen sulfide (H2S) in non-desulfurised biogas can be extremely toxic, even in lowconcentrations.

In closed rooms, with low elevation (e.g. cellars, undergroundrooms etc.) asphyxiation may be caused by the displacement ofoxygen by biogas.

Biogas is lighter than air, but it has a tendency to separate intoits compounds. Carbon dioxide, which is heavier, so it sinks tolower areas while methane, which is lighter rises to theatmosphere.

For these reasons, in closed spaces, precautions must be takenin order to provide sufficient ventilation.

Furthermore, safety equipment must be worn (e.g. gas warningdevices, breathing protection etc.) during work in potentiallydangerous areas.

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Microbiological Risk

Wastes of animal and human origin, used as Biogasfeedstock, contain various pathogenic bacteria, parasitesand viruses. Pathogenic species that are regularly presentin animal manures, slurries and household waste arebacteria (e.g. Salmonellae, Enterobacter, Clostridiae,Listeria), parasites (e.g. Ascaris, Trichostrangylidae,Coccidae), viruses and fungi.

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Microbiological Risk

The microbiological risks exist at the beginning of theprocess i.e. in the handling of organic (waste products) bythe personnel.

Digestion of excreta in the biogas tank greatly reduces thishealth hazard by killing the responsible pathogens, bacteriaand so on. So Slurry after production of biogas is very safe touse.

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HSE

Issues

Explosion

Fire

Mechanical

Danger

Electrical

Safety

AsphyxiationVeterinary

Safety

Air Pollution

Leakages

Waste

disposal

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Safety Precautions

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ZONE 0

• Flammable gases in atmosphere for long period

• This Zone does not occur in biogas plant

ZONE 1

• Flammable gases in atmosphere for short period

ZONE 2

• Flammable gases in atmosphere likely to occur under special circumstances

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