# Session 4: Safety ## Learning Objectives By the end of this session, you will: 1. Understand the key risks associated with operating a biogas plant. 2. Know the safety precautions to prevent hazards. 3. Be aware of the built-in safety features of the CREATIVenergie system. 4. Have good operational habits to ensure safe and effective use. --- ## Introduction Like electricity, bottled gas, and wood fires, biogas **can be dangerous if not handled with care**. By understanding the risks and following the precautions in this session, you can use biogas safely and effectively. ```{figure} ../assets/safety-overview.png :alt: Session 4 Safety overview infographic — risks, mitigations, EAT acronym, and safe stove use :width: 100% Overview of the key safety topics in this session: fire and explosion risks, asphyxiation, toxic gas (H₂S), disease risk, keeping others safe, the EAT daily checklist, and safe stove use. ``` --- ## Main Risks and Mitigations ### 🔥 Fire or Explosion Risk Biogas contains methane, which is **highly flammable** and explosive under certain conditions. | Precaution | Requirement | |---|---| | Distance from buildings | At least **3 m** | | Exclusion zone | **3 m** — no ignition sources | | No smoking / fires / electrical equipment | Within **5 m** of the digester | | Metal tools | Avoid near the plant (spark risk) | ### 😮 Asphyxiation Risk Biogas can displace oxygen, creating a risk of suffocation. - Keep the digester **outside and well ventilated**. - Do **not** cover the inlet or outlet with plastic sheeting. - Install a **1 m fenced exclusion zone** to prevent access by children and animals. ### ☠️ Toxic Gas Risk (H₂S) Biogas contains small amounts of **hydrogen sulfide (H₂S)**, which is toxic and corrosive to metals. - Ensure **good ventilation** around the plant. - **Never enter the digester** — even if recently emptied. Gases linger inside. - Use a **H₂S filter** (steel wool works as a cheap option) in the pipe before the stove. Replace monthly. ### 🦠 Disease Risk The slurry contains bacteria that may carry disease. - Avoid direct contact with digester contents. - **Use gloves** when loading dung. - **Wash hands thoroughly** after working with the system. - Protect cuts and scratches. - **Keep children away** from the plant. ```{danger} **Under no circumstances should you enter the digester.** This is highly dangerous — risk of gas poisoning (H₂S), asphyxiation from lack of oxygen, and infection from slurry. People have died from entering digesters. ``` ### 👥 Keeping Others Safe Once built, make sure others are not harmed: 1. **Cover the inlet and outlet** — they are deep and people could fall in and drown. 2. Put a **fence around the digester**. 3. **Cover the digester bag** to prevent damage and puncturing. 4. Check valves operate correctly regularly. 5. Ensure the **cookstove is in good repair** and not leaking. 6. If you detect a leak (digester depressurising or rotten egg smell), **get it fixed immediately**. --- ```{raw} html

⚠️ Safety Zone Diagram — click each zone

Each coloured ring represents a different safety requirement around the digester.

👆 Click a zone to see its rules.

``` ```{raw} html

🔍 Spot the Hazards — click each marker to reveal the risk

Six hazards are hidden in this scene. Click the orange circles to find them.

Found: 0 / 6

👆 Click any pulsing marker on the diagram above to reveal the hazard.

``` --- ## Safety Features of the CREATIVenergie System | Feature | Purpose | |---|---| | **Biogas Plant Cover** | Protects against physical damage and UV exposure | | **Main Gas Valve** | Quick gas shutoff — **must be shut off at night** and between each use | | **Bubbler** | Prevents flame flashback from reaching the digester | | **Pressure Release** | Excess slurry overflows through inlet/outlet at high pressure — prevents dangerous over-pressurisation | | **Inlet/Outlet Covers** | Prevents people and animals falling in | ```{figure} ../assets/safety2.png :alt: Safety features and safe stove use guide — gas valve, bubbler, H2S filter, and stove lighting procedure :width: 100% Key safety components of the CREATIVenergie system and the correct procedure for safe stove use. ``` --- ## Daily Safe Operation: The EAT Acronym To ensure safe operation, remember **EAT**: - **E** — Establish a **1 m exclusion zone** around the plant - **A** — Assess the system regularly for **damage or leaks** - **T** — Turn off the **gas valve after use** ```{raw} html

🧠 EAT — Daily Safety Checklist

E

Establish

Fence off a 1 m exclusion zone — no children or animals

A

Assess

Check regularly for damage, leaks, or rotten-egg smell

T

Turn Off

Shut the gas valve at night and after every single use

``` --- ```{raw} html

🔍 Suspected Gas Leak? Follow these steps

Click each step as you complete it. If you find a leak, follow the action below.

``` --- ## Safe Use of a Gas Stove For those new to gas cooking: 1. Light a **match first**, then turn on the gas. 2. Ensure the **flame ignites properly**. 3. Adjust to a **blue, steady flame** — no smell or excessive noise. 4. Turn the gas **off after cooking**. --- ## 🎯 Practice: Identify the Hazards ```{raw} html

⚠️ Click on the Hazards

Six situations are shown below. Click the ones you think are hazardous — then check your answers.

``` --- ## Session 4 Quiz ```{raw} html ``` --- ## Key Reminders - Always maintain a **1 m exclusion zone** around the digester. - **Turn off the gas valve** after cooking every time. - **Regularly inspect** the system for damage. - **Never enter the digester** for any reason. Next: **[Session 5: Digestate & Fertiliser](session5-digestate)**