Open Source; Low Cost In Field Biochar Ovens and Kilns

• These infield biochar ovens and kilns have been developed as a simple and low cost method of eliminating the large amount of pollution and greenhouse gas produced when crop residues and greenwaste from land clearing is burnt in the field.

• A novel method of firing the ovens has been developed that ensures that maximum biochar yields and maximum nutrient availability. This method is based on traditional Nepali and African farmer practice.

Traditional Practice in Nepal

• Soil in an area greater than 5 sq meters is dug up. Straw and grass is laid on top of the soil and smoldering dried cow/buffalo dung cakes mixed with straw are laid on top of these residues. More twigs and leaves are placed on top of the dung and then this is covered by soil, mounding up systematically from the outside.

• The dung slowly smolders for 3 days at which time the soil has

changed to a lighter reddish colour and the biomass to biochar. The charred material is worked into the ground and left for three weeks before the millet crop is planted. After this time the soil has a very slight smell of pyroligneous acids. Our informant said the millet may not germinate and the seeds may not set if the charred biomass is not incorporated into the soil. If germination is a little slow, a small amount of urea is added. After the millet is harvested either wheat or potatoes are grown.

Nepal Women make biochar Using a Simple Earth Kiln

Preparing GroundLaying biomass on soil; Smoldering dung in pot next to biomass

Laying smoldering dung on biomass

Putting leaf litter onsmoldering dung

Loosely covering the smoldering dung and biomass and allow to smolder for 3 days. Temperature is low and a lot of smoke chemicals produced

Flare shroud

Small fan or Bellows

air for tar cracking

25mm square hollow section legs

Mixed biomass, minerals and clay. Layer can extend into the ground

240mm

50mm diameter air for starting the pyrolysis process.

Optional; Small LPG burner to burn smoke and ignite syngas

50 socket screws into drum’s 2 inch BSP opening

25 or 40 mm angle

300mm

85mm

170mm

240mm

750mm

900mm570mm

50mm diameter air pipe for starting the pyrolysis process. 2 rows *14 6mm diameter holes spaced every 10mm

thermocouple

50mm Insulatation

Outline InstructionsEach biomass and soil is different so you will need to experiment. Here is a general

procedure for firing the kiln

• Mixed very dry biomass (a grass or straw is best), Minerals (e.g. dolomite, rock phosphate/basalt dust and clayey soil is put in a box as per the traditional practice shown. Put dry manure on top

• Dry manure is ignited as per the last slide• More biomass is added and covered with a thin layer of soil• Kiln is placed over the box. If you have a thermocouple place in the bed

of biomass• Air is allowed to enter to get a flame burning. It is recommended to use a

gas burner ensures no smoke if there is access to LPG. If LPG is not available make a torch from a stick with a piece of cloth that is ignited can help stop the emission of smoke

• Fan is turned on so air mixes with volatiles. If Fan and power is not available a hand bellows will do.

• The bottom air holes at the front of the kiln can be fully or partly closed once the flame is self sustaining

• When there is no flame air air at the top of the oven is shut off and kiln allowed to cool

Biomass with clay

40mm square tube Frame with sheet steel

Rigidized refractory wool

2.7 m

1.8

m

700mmLPG burner to crack smoke, ignite syngas

150mm Secondary air pipes

150mm holes for start-up air. Burner inserted to ignite top

Flare shroud

Heat shield with gas holes

Baffle with hot air or exhaust from diesel engine flowing up the side

LARGE INFIELD PYROLYSER

• Reduce emissions when crop residues & greenwaste are field burned.

• Covers 7m3, ~2 tons biomass

• Carried and placed by tractor

• External gasifier provides hot air for drying / torrefaction to ~ 200oC, <15% moisture

• Small genset powers fan, sends flue gas into kiln

• Top of biomass is ignited through lower airholes, later closed

• Volatiles mix with air and burn at the top of kiln, radiating heat to drive pyrolysis, which progresses downwards

Water sprays

CONCEPT

Sacrificial shield

Hot air pipes & baffles

3.0m

Hot air/exhaust flow

Airpipes above shieldAirpipes below shield 2mm mild steel sheet bolted to

40mm square tube frame with expansion holes

Two 600x600mm flues, flare shrouds not shown

Secondary airpipes of 150mm SS exhaust pipe with graduated air holes for equal pressure

2mm mild steel sacrificial shield with 0.6m2 of gas slots supported on ledges at tops of walls

Hot air pipes of 150mm heavy gauge steel with graduated air holes welded to 3mm baffle plate

Weighs 765kg + exterior pipes, fan, generator, controls

Cost: $20,000

LARGE SHEET-METAL INFIELD PYROLYSER

CONSTRUCTION DETAILS– PROTOTYPE

Ledge to support shield

The BIG ROO INFIELD PYROLYSER

Demonstration of TLUD Oven at Binh Thanh Commune

Prepare the feedstockPut a thin layer of slurry of clay and lime on the straw. Cut wood andBamboo to fit across the drum

Place straw, then rice husks, then bamboo/wood in layers about 20cm high

Make sure steel skirt around bottom of drum is open to allow air to come in.Light fire.

Demonstration of TLUD Oven at Binh Thanh Commune

Putting lid on Reducing Air Cutting air off

Reducing Temperature to about 450-550C with spray water

Testing Quality of Char

Dry Biomass In = 23kgDry Biochar Out= 8.6kgYield = 37%

High yield due to high ash content of the rice husk and aged bamboo and wood

My Design at Home With Hot Water