Purpose

This guide is for course organisers preparing materials for biochar cook stove workshops. The focus is on designing the stove according to available materials and sourcing recycled components, rather than providing step-by-step construction instructions.

The principle is simple: we make use of whatever materials we can get for free or cheaply and design the stove around them. This is not a build guide — it is about understanding what materials to bring so they can be used and adapted during the course.

1. Burn Chamber

The burn chamber is the heart of the stove. A range of materials can be used depending on availability, and the design can be adapted accordingly:

• 50 litre steel drum: A common option, though not always easy to source and may require some time to find.
• Beer barrel (50 litre typical, 100 litre rare): Durable, lasts longer, produces more biochar.
• 30 litre drum: A smaller option, though less practical if you plan to include an oven.
• 200 litre drum: Can be adapted depending on design and availability.
• Gas cylinders: Can be used, but require extra care (see safety note below).

⚠ Safety note: Gas cylinders and beer barrels can be pressurised. They must be fully depressurised and made safe before cutting. This is critical. We cover how to do this safely during the course. I also have a video showing how to safely decompress a beer barrel, which should be followed before working with them.

Sourcing tips:

• 50 litre drums: car garages (allow extra lead time), industrial suppliers, second-hand markets
• Beer barrels: pubs willing to give away empty barrels
• 30 litre drums: smaller workshops, garages, or catering suppliers
• 200 litre drums: scrap yards, industrial sites, skips
• Gas cylinders: scrap metal yards (only if confident in safe handling)

2. Outer Barrel / Baffle / Oven

A 200 litre steel drum is commonly used as part of the upper assembly, but other materials can also be adapted depending on availability.

Corrugated steel sheets can also be used to form a baffle, lid, or outer structure where full barrels are not available.

Sourcing tips: 200 litre drums: car garages (allow time), scrap metal yards, industrial skips

3. Chimney

The chimney directs gases out of the stove. The cheapest and easiest material is a 2.5 kg tin (tomato or paint tin). Other options include:

• Corrugated steel sheet rolled into a tube
• Scrap steel pipe of appropriate diameter

Sourcing tips:

• 2.5 kg tins: behind restaurants, catering kitchens, or workshops
• Corrugated sheet: skips, construction sites, old fencing, warehouses
• Scrap steel pipe: metal recyclers, building sites

4. Corrugated Steel Sheets

Corrugated sheets are versatile and can be used for:

• Baffles inside the stove
• Lids for the burn chamber or oven
• Chimneys if no tin or pipe is available

Sourcing tips: skips, construction sites, old fencing, warehouses, builder friends

5. Finishing Materials

Small additional materials make the stove easier to use:

• Wooden handles for the oven door: logs or timber battens (~4 pieces)
• Long screws (~30–40 cm, 12 pieces) to attach handles
• A hinge for the oven door
• Bolt(s) (3–6 depending on hinge) to attach the hinge securely

Practical Tips for Course Preparation

• Plan 2–3 weeks ahead — barrels and large tins may take time to become available.
• Network locally with garages, restaurants, pubs, and builders for scrap materials.
• Focus on what is available and design the stove around these materials. Adaptability is key.
• This is not a construction guide — materials will be adapted and built during the course.
• Do not worry about new or expensive materials — recycled and free materials are sufficient.