biochar rocket stove building instructions

8/12/2019 Biochar Rocket Stove Building Instructions

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Biochar

Biochar is charcoal intended to be used as a soil admixrather than to be burnt. There are 2 main reasons for this; 1, To improve crop yields by increasing the soils nutrientholding capabilities, increasing moisture retention, reducingacidity and increasing the amount of soil micro organisms.2, To stabilise the carbon in biomass and thereby sequesteratmospheric carbon dioxide. There are environmental and economic advantages toproducing your own biochar as a by-product of cooking orgenerating domestic heat and hot water. It is important notonly to make biochar yourself or to obtain it from a knownlocal source, but also to ensure that it is made in such away that the heat produced is used ef ciently.

Issues of peak oil and climate change mitigation mean

that we should be looking for alternative energy sources tofossil fuels. If we are to wean ourselves off our fossil fueladdiction, we are going to have to use biofuels very wisely.We can not afford to be wasteful with wood, even if thatwood is seen as a waste resource.

Rather than building up an industry which produces,packages, transports and sells biochar, it would be betterwith regard to environmental concerns to develop domesticheating and cooking systems which burn wood gasesand leave biochar unburnt to be used by the person whoproduced it or sold or given to local neighbours.

There is a rapidly growing market for biochar and newindustries are emerging which produce, package and sellbiochar. For several reasons I believe that it is better toproduce your own biochar or to buy biochar producedlocally from a known source.

1, The feedstock from which biochar is made may notbe known or regulated. Biochar may include soot andother byproducts from the incineration of plastics or otherenvironmentally hazardous substances.

2, The CO2 and other environmental pollutants releasedfrom burning fossil fuels to produce, package and transportbiochar may be greater than the CO2 sequestered by thebiochar.

3, The biochar may be produced while wasting the heatresulting from burning the pyrolisis gases.

4, It is possible that commercial scale biochar productioncould result in unsustainable woodland management,deforestation or even land grabbing (practices that havebeen seen with other biofuel production.)

5, Purchasing enough biochar in a large enoughquantity for it to have any noticable effect in terms of soilimprovement may prove prohibitively expensive.

6, Poor biochar production techniques (such as the use ofcharcoal kilns or poorly designed retorts) may result in

particulate emissions (unburnt smoke) which contribute toglobal warming.If we are not careful, biochar industries maywell waste wood and contribute to atmospheric CO2 levels.

Keep production local!

I have combined design features of rocket stoves and anilastoves to produce what I call a modi ed rocket stove. Thisstove is operated in a similar way to a rocket stove but hasthe advantages that it produces more heat than a rocketstove and it produces biochar.

The pyrolysis cookstove technology which is beingimplemented across various developing countriesdemonstrates ef cient, intelligent use of wood as a biofuel.However nobody has yet looked into ways of implementingthe principles of this technology in the developed world.

Before going on to propose a heating system which issuitable for use in the developed world and which producesbiochar, I am going to brie y introduce 3 simple stovedesigns. The tlud and anila stove are worth mentioningbecause, when used as biochar producing cookstoves,they demonstrate the ef ciencies and bene ts mentionedabove.

I mention the rocket stove because, although it is not abiochar producing stove, it has design features which allowef cient combustion and ef cient heat retention.

I have combined design features of rocket stoves and anilastoves to produce what I call a modi ed rocket stove. Thisstove is operated in a similar way to a rocket stove but hasthe advantages that it produces more heat than a rocketstove and it produces biochar.

The tlud

Designed by Paul Anderson, the top light upward draught(tlud) gasifying cook stove works on more than just onelevel. It is a very ef cient cook stove, producing a lotof heat from a small amount of wood. It is smokelessand it produces biochar. Paul Anderson has also beeninstrumental in getting these stoves distributed andused in developing countries where wood or charcoalis otherwise used in conventional res for cooking. Bybeing more ef cient, less wood is needed. By beingsmokeless, diseases and deaths caused by smoke in livingspaces are reduced. By producing biochar, subsistencegrowers are able to mantain soil fertility and improve soilstructure, biological activity and moisture holding capacity.

Atmospheric carbon is also being sequestered by the useof these stoves.

Tlud stoves are basically a container with restricted airinput to the bottom of the container, lled with biomasswhich is lit from the top, and forced air blown through holesat the top of the container. This air mixes with the risingsmoke (wood gas) causing it to combust.

The Hybrid Rocket Stove and Biochar


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When the ame from the combusting smoke (wood gas)dies down, charcoal sticks are left in the stove. These haveto be quenched with water to prevent them from burning upbefore they can be used as biochar.

The Anila Stove

Designed by R V Ravikumar, the anila stove consists of acombustion chamber surrounded by a second chamber,the retort. The retort has a removable lid or base so that itcan be lled with biomass such as wood chip. A re is builtand lit at the top of the inner combustion chamber. This recauses the wood chip in the retort chamber to heat up.

Because there is not enough air in the retort for combustionof the wood chip, pyrolisis occures instead. Pyrolisis iswhen something burns when deprived of oxygen. It cantproduce a ame, so smoke (producer gas) is given off.

There are holes in the bottom of the combustion chamber.The only place where the wood gas from the retortchamber can go is through these holes into the combustionchamber, where they combust.

The retort can then be opened to empty out the biocharand re ll with wood chip.

The Rocket Stove.

Rocket stoves, developed by Larry Winiskari, are verysimple in terms of design; they consist of an elbow of pipesurrounded by heat resistant insulation. They have twofeatures which have made them of interest;

1, They are ef cient in terms of combustion.

2, They allow for ef cient heat capture.

Ef ciency of combustion also equates to clean, i.e.smokeless combustion. Smoke is unburnt particles.

There is little point in having ef cient combustion if thatheat is not also captured ef ciently. Because the stove isinsulated, it does not rely on having an insulated ue pipeto generate air ow. It is therefore possible to direct the uegases horizontally and through a thermal mass.

Rocket stoves do not produce biochar. I have included thisdescription of rocket stoves here because I have used therocket stove design but introduced two design changes inorder to enable it to produce biochar.

The advantages of ef ciency of combustion, ease of heatcapture and ease of lighting are retained in the modi edrocket stove.

The Biochar Rocket Stove

It is my belief that the principles of biochar cook stoves canbe applied to developed as well as developing countries.This would help us to reduce our ecological footprint,sequester CO2 and produce a greater proportion of ourfood locally. The modi ed rocket stove is clean, easy tolight, does not require charcoal to be quenched, can be

tted with a self lling hopper and auger and is more suited

to domestic use in developed countries than are the anilaor tlud.

A rocket stove can be hybridised with an anila stove byreplacing the insulation of a rocket stove with biomass suchas woodchip.

These stoves have 2 advantages over rocket stoves;

1, These modi ed rocket stoves produce more heatthan conventional rocket stoves because, as well as thecombustion of the sticks in the combustion chaber, thewood gases also combust.

2, They produce biochar.

Like anilla stoves, the only place for the wood gasesproduced in the retort to go is through the holes in thebottom of the combustion chamber where they thencombust, adding to the heat being produced.

These stoves also have 3 advantages over anila stoves;

1, By feeding the combustion chamber from the bottom,the top of the stove is left free to be attached to a heatexchanger.

2, They are easier to light than anila stoves. Any smokeproduced when rst lighting is directed away from the livingspace up the ue.

3, They can be allowed to burn after pyrolisis has nished,running as a rocket stove.

The diagram (Fig. 1) shows dimensions which have beenshown to work. These dimensions can be scaled up butthis size is suitable, for example, as a small scale domesticwater heater.

The stove shown in the diagram is the basic version, ahopper and removable bucket can be tted (ensuringthe retort remains air tight) in order to make lling andemptying easier.

A fan has been tted which forces air into the combustionzone, immediately above the point at which the pyrolisisgases enter.

Although the stove will burn and produce biochar withoutthe aid of a fan, the ames produced are orange in colour,indicating unburnt soot or carbon.

Unburnt carbon released into the atmosphere is acontributor to climate change.

The heat output of the stove is signi cantly increased withthe forced air, as the particles are then fully combusted (the

ame should turn white).


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biochar rocket stove building instructions

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