Wood Cook Stove

8/14/2019 Wood Cook Stove

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SIMPLE PLANS TO BUILD

THE JUSTA STOVE

The Justa Stove is also known as La Estufa Justa, the Just stove, the Ecostove or El Ecofogon.How to build one of the new generation of fuel efficient

stoves with chimneys.

text

The Justa (pronounced Hu-sta) stove was developed through the coordinated ef-forts of the people of Central America, Trees, Water, and People, Rotary Interna-

tional and Aprovecho Research Center

Text: by Peter ScottIllustrations: by Tony Wiley, Brian Thomas and Ethan Hughes

For more information about the Justa Stove or if you would like assis-tance in designing a stove for your community please contact us at:


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The body of the Justa stove can be built with a variety of different ma-terials, such as cement, clay & sand, brick, adobe, or metal. This guideexplains how to construct the stove with brick but other plans areavailable to build the Justa with cement and metal.

The type of material (cementbrick , adobe or metal)) that isused for the exterior stovebody will not have a great im-pact on the performance ofthe stove. Special materialsare not needed for the stovebody. The stove will functioneffectively as long as the bodyof the stove can support 5 potsand can withstand tempera-tures of up to 500 degreesFahrenheit.

This cement Justa is being built byHelps International in the Guatema-lan Highlands. Three individual ce-ment pieces are cast in fiberglassmolds and then assembled on site.The molds are easy to transport andprevent design inconsistencies.

This metal Justa with oven is be-ing constructed by Ahdesa inHonduras and by Prolena in Nica-ragua. The metal Justa is approx.30% more expensive but it al-lows for mass production andease of transport.

e

BUILDING WITH METAL OR CEMENT

See page 16 for contact information for Helps, Prolena and Ahdesa.


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The Justa type stoves are built using principles that can be adapted to build astove to suit a particular cooking need. Because one stove design will not workin each community, we offer a number of stove models to choose from:

This stove is thesame as the origi-nal Justa stove yet

it features 2 potsthat are sub-merged directlyinto the fire flowpath. When usedwith 3 pots it is50% more effi-cient than theoriginal Justa.

The single-potRocket stove isless expensive

and more effi-cient (25- 30%)than the JustaStove. It is idealfor cooking out-side or in areaswhere a chimneyis not needed oravailable.

THE ROCKET STOVETHE IMPROVED JUSTA STOVE

THE ROCKET RING STOVE

With the ringsin place, mul-tiple pots ortortillas can becooked at thesame time.The rings canalso be re-moved for usewith individ-ual round bot-tom pots.

THE HAYBOX COOKER

The haybox worksby retaining heatinside a layer ofinsulation such asstraw, wool orfoam. The hayboxcan reduce fuelconsumption by70% and is simpleand inexpensive tobuild .

For more information about these stoves or if you would likeassistance in designing an appropriate stove for your commu-

nity please contact Aprovecho Research Center

DIFFERENT STOVES FORDIFFERENT NEEDS


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TOOLS AND MATERIALS FORBUILDING THE JUSTA STOVE

Rocket combus-tion chamber.

See pages 6 & 7 .

Cooking griddle.

1/8th inch steel cook-ing griddle. See page8.

Chimney.6-20 of 4diameterchimney

pipe. Seepage 9.

Stove body. 50 (5by 8) fired claybricks or 20 adobeblocks. See page 11.

Stove base. Thiscan be made fromwood, brick, ce-ment, or adobe.See page 10.

Wood ash, pumicerock, or vermiculiteto fill the front halfof the stove body(13 by 12 by 14).Approx. three 5-gallon buckets of

insulation 2 wheel barrows of

clay /sand mortarfor constructing thestove body (30%sand/ 70% clay)

Dry sand or earth tofill rear half of stove

body (13 by 12 by14). Three 5 gallon

buckets White clay (for

painting outside of

stove) 4 tin can with plas-

tic or metal lid One piece of rolled

steel (1/32 by 12by 16)

OTHER REQUIRED MATERIALS TOOLS

Shovel Wheelbarrow 3 carpenters

level Aviation snips Hacksaw Square

Hammer Trowel


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BUILDING THE STOVE BODY

53

24

18

22

14

1/2 Bricks

45

8

12

28

107

4

4

The internal width and length of the stove are the most important. The internal dimensions

will always be 12 wide by 28 long (assuming you are using the recommended 14 by30 cooking griddle). These plans are designed for use with 5 bricks . If you are using lar-ger or smaller bricks your external dimensions will change. For example, if you use 6bricks then the external measurements of the stove will change to 24 by 47.

1 (inch)= 2.5 cm

Use the clay/sandmortar to lay the(pre-soaked) bricks.Use the level and

the square whenbuilding to be surethat the stove is auniform shape.Also be careful tomaintain the properdimensions (12 by28) as you buildeach brick course


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BUILDING THE STOVE BASE

To minimize theuse of materials thestove can be built in

a corner of thekitchen so that only2 walls are neededinstead of 4. If youprefer to build itaway from the walljust double theamount of materialsgiven for 2 walls.Once constructedthe base can befilled with earth orrocks.

For a cement base2 walls: 10 cementblocks and 1/2 bag ofPortland cement.

4 walls: 20 blocks and 1bag of Portland cement.

For a brick base2 walls :35 bricks and 2wheel barrows of clay/

sand mortar.

For an adobe base2 walls: 20 adobe blocksAnd 1 1/2 wheel barrows

of clay/sand mortar.

For a wood base.Construct a woodtable that can sup-

port 400 lbs.

NOTE: Adobe blocks are the most environmentally friendly option for buildingthe base and the body of the stove because adobe blocks are not fired like claybricks. The plans use bricks only because, in the USA, and in many parts of LatinAmerica, fired bricks are easier to obtain than adobe blocks.

18

53

24

The base for the stove can be built from brick , adobe, cement, wood, or metal. Even better than

constructing a new base is to use one from an old, existing stove. The height and length of thebase can be altered to suit individual needs. In Latin America and in these plans the base is built18 high and 24-26 wide (depending on the width of the bricks). See following page for anote on brick width.


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THE COOKING GRIDDLEThe griddle can be made from rolled steel or cast iron. For rolled steel use no less than 1/8th ofan inch thick. This is ideal if you are producing multiple griddles from a 4 by 8 sheet of steel

cut the griddles 16 by 32. If you are cutting from a 4 by 10 sheet, cut the griddles 16 by30. The smaller griddle must be compensated with a smaller stove body (from 12 by 28 to12 by 26). The dimensions of the griddle can be elongated (32- 40) and widened to nomore than 20.

16 16 16 16 16 16

32

16

32 32 32

One 4 X 8 sheet of rolled steel willproduce nine 16 X 32 griddles

30 30 30 30

16

16

One 4 X 10 sheet of rolled steel willproduce twelve 16 *X 30 griddles

16 X 32 Bend 1lip aroundgriddle

14 X 30

Note: cast

iron can beused butshould be nomore than1/4 to main-tain effec-tive heattransfer.

If the griddle begins to warp it ispossible to weld 1 by 1/8th an-gle iron on the inside of the lips.

1X 1/8th

16

1 2 3


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THE ROCKET COMBUSTION CHAMBER

The combustion chamber can be made from re-fractory cement, refractory ceramic, 1/8th steel,

or cast iron. We are also experimenting with aceramic tile (see page 7) from Guatemala andour own refractory mix.In Honduras, a womens cooperative makes ahighly durable ceramic combustion chamber thatcan last up to 10 years. See page 16 for contactinformation.Clay pottery often isnt effective but experimen-tation with local materials can often lead to posi-tive results.These plans call for an elbow that is 5 in diame-

ter (internal) by 10 tall by 11 long (see photo).

For optimumefficiency, theRocket stoverequires an in-ternal shelf. Theshelf should be

made from re-fractory ceramicor 1/4 steel .When in place,the shelf should

create a 1

unob-

structed gapbetween thewood and the

bottom of thecombustionchamber

10

5

11

1 gap


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ASSEMBLING THE JUSTA

If possible build the stove body

with the Rocket elbow combus-tion chamber in place. This willallow you to build a strong frontwall that fits snugly around thecombustion chamber. Otherwiseinsert the elbow after the stove-

body is complete. The mouth ofthe elbow should be supported

by one brick (see photo below).

This will raise the elbow 2inches form the floor of thestove body. This space beneaththe elbow should be filled withinsulation. The elbow shouldnot be touching the floor of thestove body.

1 brick sup-ports theRocket elbowcombustionchamber.

The elbow should bepositioned so that thetop of the combustionchamber sits 1/2 be-low the exterior wallsof the stove body.

Use the clay/sand mixture to fillthe gap between the combustionchamber and the exterior wall.


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If possible, fill the entire stove with insulation.However, if there is a shortage of insulation, theback corner can be filled with dry earth or a mix-ture of tin cans/dry earth or glass bottles/dry earth.


Once the elbow is positioned 2above the floor of the stove body, 1/2below the exterior walls, and 3 from thefront wall (see photo right) - join the 2pieces of the elbow together with the sameclay/sand mix that was used for mortar.

Fill the stovebody withinsulation(dry woodash, vermicu-lite, or pum-ice) so that itis level withthe exteriorwall.

4

2

The 1 lip of thegriddle creates a1 passage thatallows the hot fluegases to travelabove the insula-tion and below thegriddle.

3

KEEP THIS SPACE UNOBSTRUCTED. DONOT FILL IN THE GAP OF THE INTERIOR

WALLS LAST BRICK LEVEL

The insulationshould begin toslope down 3 inchesbefore it reaches theinterior wall. Thiscreates a passagethat allows the hotflue gases to exit to

the chimney.


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Has generated an average fuel savings of 40% in Central America. Sav-ings depend on the efficiency of the previous stove

Removes 100% of wood smoke from the house and produces 35-85%less green house gases than an open fire.

Is easy to construct. 2 people can build a Justa in 4-8 hours. Is long lasting. In Honduras we are building Justas with a life expec-

tancy of 10 years (not including chimney) for approx $50. Has a high level of acceptance in many Central American communities.

The Justa stove is for people who make tortillas, havemultiple pots, and cook indoors. The Justa:

If yes, then considerbuilding an unventedstove outside the house.Unvented stoves canoften be more efficient ,easier to build and longerlasting. If the chimney isnot replaced when iteventually degrades itwill expose the family tomore smoke than if theyhad continued to cookoutside.

Are people cooking

outside?

Is Liquid Petro-

leum Gas (LPG)

readily available?

Are they build-

ing conserva-

tive open fires?

Are they using

round bottom

pots ?

If you answer YES to any of these questions, you should RECON-

SIDER introducing the Justa stove into your community. See thenext page for other designs that might be more appropriate or contactAprovecho for more information.

If yes, than considerencouraging a switch toLPG. In many southerncountries wood is notsustainably harvested soeven an improved woodstove can lead to longterm forest degradation.There is some evidencethat LPG stoves pro-duces less green housegases than wood stoves.

If yes, considerintroducing a hay-box or an unventedstove outside thehouse. A small,carefully tendedopen fire can bevery efficient. Un-fortunately, thistype of fire is un-common in mostparts of CentralAmerica.

If yes, considerintroducing therocket ring stoveor a regular Rocketoutside. Roundbottom pots willnot work with theJusta due to poorcontact with thecooking surface. I fthey have only onepot, consider intro-ducing a Rocket

The Justas chimney, combined with its high combustion efficiency,make it an ideal stove for people who are aware of the health hazards ofinhaling wood smoke. However, the Justa stove is not the ideal stove for

every cooking situation.

Here are some things to consider before introducing the

Justa stove in your community:


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THE JUSTA CHIMNEY

There are at least 3 materials options for

the chimney

Galvanized Steel

Pros Inexpen-

sive

readilyavailable

Light

Easy tohandle,

transportand clean

Diameter: 3 1/2 - 4 1/2Height: at least 10 above the roof .Ideally the chimney should be above the peak ofthe roof but usually this is not an option due tocost considerations

Cement water pipe

Clay pipe or blocks

Better material options exist, especially in the USA. Any commonly acceptedchimney material such as black chimney pipe , stainless steel or masonry blockscan be used with the Justa.

Cons Questionable

durability (1-4 years)

Toxicity inmanufactur-ing process

Susceptible to

acid rain deg-radation

Pros Very dura-

ble (10years+)

Can becheaper thanZinc

Cons Less efficient

(higher mass)

Difficult totransport, han-dle and clean.

Earth quakehazard

Need to buildsturdy base forsupport

Pros Very inex-

pensive

easy totransportand handle

Very dura-ble (10years+)

Cons Earthquake

hazard

Not readilyavailable.

Difficult toclean


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Constructing thesoot removal

chamber

Take the 4 tin can andcut the bottom out of it.

Insert it in the opening inthe back corner of thestove.

Use clay/sand mortar tofill the space betweenthe can and the bricks.

Seal the can with theplastic or metal lid.

Remove the lid every

few months and sweepout any soot that has ac-cumulated beneath thechimney.


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CONNECTINGTHE CHIMNEY

Take a piece of 1/32 steel(10 by 32) and cut a 3 di-ameter hole in the middle ofthe sheet.

Then cut twelve 1 tabs inthe circle. Bend these tabsupwards.

You now have a 4 hole with1 vertical tabs. Lay thisacross the antechamber and

seal with sand/clay mortar.

Place the chimney on top ofthe hole (with the flanges in-side the chimney pipe).

Hold the chimney pipe steadyas you lay the 4 bricks snuglyagainst it.

Place mortar between and un-der the bricks and betweenthe bricks and the chimney.


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A s s e m b l i n g t h e J u s t a continuedTHE ROCKET COMBUSTION CHAMBERUsing a ceramic floor tile to build the combustion chamber.

Take three baldosas (1 by 12 by 12). Cut

all 3 tiles to 1 X 10 X 10. Cut the AB tilein half. This will leave you with two 5 by10 pieces. Then take the second tile (CE)and remove a 5 by 5 square (E) and thentake the third tile (DF) and remove a 5 by5 square (F).

Then connect the pieces as shown. Use a50% sand/ 50% clay mortar to connect thepieces. Once in use, the weight of the insu-

lation will keep the elbow in place but itshould be checked periodically to assurethat it is still properly connected.

The baldosa is a ceramic floor tile that offers an inexpensive option to other refractory combus-tion chambers. The baldosa in Guatemala costs US$.25 per tile or US$.75 for an entire elbow.This compares very favorably to the US$6-7 for the refractory ceramic or refractory cement el-bow that is currently being produced in Honduras. However, the refractory ceramic and refrac-tory cement elbow are reported to last for 10 years+, whereas the baldosa has only been in use inGuatemala since February 2001 (approximately 6 months as of this printing). Please contact usfar an update on the availability and durability of the baldosa.

The final dimensions of the elbow will be

the same as the ones listed on the previ-ous page but with one exception. Theelbow will be 10 long instead of 11

Baldosa elbow dimensions: 10

tall by 10 long by 5 in diame-

ter.


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CCONTACT INFORMATION FOROUR STOVE PARTNERS

TREES WATER AND PEOPLE (TWP)is coordinating stove projects throughout CA. Contact Stuart Conway. 633 SouthCollege Avenue. Fort Collins, CO 80524. Tel: 970 484 367. Fax: 970 224 1726E-mail [email protected] Website www.treeswaterpeople.org

HELPS INTERNATIONALis building cement Justa stoves with molds and is experimenting with the ceramictile baldosa. Contact: Richard Grinnell 502-318-5756. email [email protected] page: www.helpsintl.org

ASOCIACION HONDURENA PARA EL DESARROLLO

AHDESA in partnership with TWP, is building stoves in Tegucigalpa and Mar-cala.Contact Ignacio Osorto. Tel: 235 5343 /231 0741 Fax: 504 239 0883E-mail: [email protected]

RICARDO CRUZ

is constructing the portable metal version of the Justa Stove with ovenE-mail: [email protected]

NUEVA ESPERANZAproduces durable ceramic combustion chambers for approx. US$ 6Aldea Jocomico Pan american Highway in the dirrection of san lorenzo 10 kms

In Guatemala

In Honduras:

In the USA:


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PROLENA NICARAGUA

is building portable metal Justa Stoves (Ecostove)Contact Rogerio Miranda 365 9278 088 34144 E:mail [email protected]

COOPERATIVE LEAGUE OF THE USA (CLUSA)is also building portable metal Justa stoves in ManaguaContact Julie Varron or Stanley Kuehn at [email protected]

In Nicaragua

In El Salvador

FUDEMCO (FUNDACION PARA EL DESARROLLO EMPRE-SARIAL COMUNITARIO) is building modified Justa stoves in EL CocoContact Armando Hernandez Tel/fax 260-7063 e-mail [email protected]


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Placing thegriddle onthe stove

body


1 Build a lip (1high by 3 wide)along the edge of thefront wall and the twoside walls of the exte-rior stove body

3 Once the lip isdry, fill the 1gap with dry

wood ash.

2 Place the griddleon the stove body,leaving a one inchgap between the lip

and the griddle.

Stove body

griddle

lip

Exterior wall

griddle

Wood ash

YOUR JUSTA STOVE IS NOW COMPLETE!

Place 2bricks in

front of thestove tosupportlong piecesof wood.

Note: the placementof the milk or cof-fee can with remov-

able lid. Be surethat the clay/ sandmixture is placedtightly around thecan and that thereare no cracks for airto pass through.

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Wood Cook Stove