Digester 2

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Methane DigestersFor Fuel Gas and Fertilizer

With Complete Instructions For Two Working Modelsby L. John Fr

!" #uilding an Inner Tu$e Digester

Fig. 21 Attachment of pipes and bucketsI hope that in these times of ever increasing pressures in the energy crisis, that thisinner tube unit will be made available to the millions on millions of people around


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the world who could benefit from it. To those on the land eking out an e istence, Idedicate this unit. As a morsel of technology, it might well benefit them more than aman standing on the moon.-- L. John Fry

Inner Tube Digester Parts List

1. Main Chamber of the Digester 2. The Plastic InsertA. The Plastic Cylinder B. The Inlet !as and "ffluent Pi#es$$ Inlet Pi#e$$ !as %utlet Pi#e$$ "ffluent Pi#e&. Attaching the Cylinder to the Inner Tube'. Inlet (ittings and Attachment of the )lurry *(eeding+ Buc,et$$ Attachment of Buc,et-. (itting the "ffluent Pi#e. (itting the !as %utlet/. The )cum Collector $$ !as %utlet Continuation0. !as ield Indicator . Pressure 3elease Bottle14. Inner Tube )torage11. Burner 12. Tem#erature1&. The Bacterial Bre51'. (eeding1-. 3emo6ing )cum and "ffluentA. )cumB. "ffluent1 . )afety Precautions$$ Precautions In !as 7sage1/. Lighting the (lame10. #8

The follo5ing inner tube unit 5as made at a cost of about 924. If it could be #roduced in:uantity the cost might be as lo5 as 92 using chea#er material.

The unit has no 5or,ing #arts and should last the normal life of the materials used.

This inner tube digester has been tested out in )anta Barbara for o6er 10 months during5hich all the ;bugs; ha6e been eliminated. It is a thoroughly reliable de6ice.


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Inner Tu$e Digester %arts List

1. Truc, or tractor si?ed inner tube 2. Ple@iglass *1 0; thic,+ /; @ 20; *or circumference of inner tube+. Ple@iglass 14; @ 14;.3. Methyl chloride li:uid *hobby sho#+ 4. Ple@iglass tubes *2; @ & + 5. 2 @ 2$inch diameter bicycle inner tubes 6. Poly6inylchloride *P C+ ta#e 7. & @ -$gallon #olyethylene buc,ets 8. -$gallon container $$ metal or #lastic $$ for scum collector 9. "#o@y resin 10. 3ubber sealing com#ound 11. 3ubber cement 12. ire 13. Pi#e ada#ter *,ind that goes from steel to #lastic+ 14. 1 '; rubber or late@ hose 15. 1 gallon Eug 5ith cor, 5ith t5o 1 '$inch holes 16. Bottle 17. T #ieces 18. Truc, inner tubes *storage+ 19. )cre5 ty#e #inch clam#.

!. Main Cham$er o& the Digester

This consists of a discarded truc,$si?ed *or better still a tractor$si?ed+ inner tube.1. Test carefully for lea,s. *Bear in mind that e6ery #art going into the digester should

be carefully tested for lea,s. Any gas esca#ing out of e6en a #inhole is a potentialcause of e@#losion.+

2. Patch o6er if necessary. If there is a large gash or hole cut that #ortion com#letelyout of the tube.

3. Ma,e a clean cut at right angles to the long circumference of the tube. This is 5herethe #lastic cylinder 5ill be inserted *(ig. 21+.

4. Thoroughly 5ash and dry the inside of the tube. The inner tube is no5 ready for the

#lastic insert.


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1. Ma,e three 2; diameter holes one on one side of the center di6ider t5o on theother side *(ig. 2& 2'+. "@act #lacement is not im#ortant but must be so close to the

baffle as to touch it and in the general area sho5n in (ig. 2'. A##ly a little glue at thetouching #oint for added strength. Allo5 at least 1; bet5een the tubes to the li# of thecylinder *(ig. 2&+. e made the holes by burning around the outside edge of the hole5ith a sim#le soldering iron. A (3"T sa5 5ould do a better Eob.

Fig. 2# $ross section of the plasticinsert

Inlet %ipe+

2. 3eam out the inlet #i#e hole to allo5 the inlet #i#e to go in at a slight angle *(ig.2'+. This angle hel#s the mi@ing in the inner tube by tending to ma,e the incomingra5 slurry re6ol6e in the tube.

3. Insert the #i#e in at an angle '; do5n into the cylinder *(ig. 2&+. The distance the #i#e stic,s out the to# of the cylinder is not im#ortant.

4. To eliminate lea,s seal the seam around the #i#e and hole 5ith= *1+ a layer ofmelted #le@iglass and methyl$chloride and then *2+ a layer of rubber sealingcom#ound a6ailable in hard5are stores.


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Gas ,utlet %ipe+

5. This #i#e is glued to the to# of the cylinder *(ig. 2&+. Again the length of the #i#estic,ing out the to# of the cylinder should be about inches. Length in (ig. 2& isabout right.

6. )eal as abo6e.

*&&luent %ipe+

7. Insert the effluent #i#e straight do5n into the cylinder to 1" from the bottom . *(ig.2&.+ Again ; abo6e to#.

8. )eal seams as abo6e. here the inlet and outlet #i#es touch the center baffle a##lya little glue to gi6e added strength to them as mentioned abo6e.


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Fig. 2% "lacing the cylinder in the inner tube

-. (ttaching the C linder to the Inner Tu$e

1. Paint the inside of each o#en end of the inner tube to a de#th of about 2; 5ith any,ind of rubber cement *(ig. 22+.

2. Insert the cylinder into the inner tube #ast the li# to a distance far enough to ensure agood seal *(ig. 2-+.

3. Ta#e in #lace 5ith #oly6inylchloride *P C+ ta#e to hold cylinder and inner tubesecurely in #osition *(ig. 2 +.

4. Then 5ind 5ire t5ice around on the ta#e. T5ist the ends of the 5ire to ma,e a 6ery

tight hold. *The 5ire and the ta#e are ne6er remo6ed.+

Fig. 2& Fastening tube to ple iglass cylinder

. Inlet Fittings and (ttachment o& the /lurr 0Feeding1 #ucket

1. Cut a 2; diameter balloon bicycle inner tube to a length of about & after chec,ing


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7. %ressure 8elease #ottle

This bottle is #laced bet5een the gas yield indicator and inner tube storage *(ig.24+. Itallo5s the release of e@tra #ressure in the inner tube storage or o6erflo5 of gas to esca#e

through the 5ater in the bottle rise to the atmos#here and dis#erse harmlessly.

1. A 12; or so dee# bottle is fitted 5ith a ;T; #iece *(ig. 2 +. 2. The tubing from the gas yield indicator is attached to one arm of the ;T; and a tubing

to storage is attached to the other arm. 3. A #lastic tubing is attached to the leg of the ;T; #iece and immersed in 0; of 5ater. 4. In the e6ent that the gas #ressure is more than 0; 5ater gauge the gas 5ill esca#e

through the 5ater to the atmos#here.

!". Inner Tu$e /torage

1. !as can be stored in one or a number of truc, inner tubes stac,ed on each other andinterconnected 5ith ;T; #ieces *(ig. 24+. Chec, for lea,s and #atch if necessary.

2. A 5eight such as #ieces of lumber are #laced on the to#most tube to create #ressure.


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!!. #urner

The gas #roduced by this digester is about /44 BT7 #er cubic foot at sea le6el *-0- BT7 at444 ft. altitude+. The a6erage daily #roduction of this system is - cubic feetH enough to bring1 2 gallon of 5ater to the boil and ,ee# it there 24 minutes. T8I) I) "


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bacteria. The inlet #i#e *set at an angle+ hel#s the mi@ing by tending to ma,e theincoming ra5 slurry re6ol6e in the inner tube.

4. Dis#ose of the feathers fiber sand etc. left in the bottom of the buc,et.

The action inside the digester is the same on any scale. The ra5 material hea6ily seededtends to s,ul, along the floor of the digester but as the bacteria 5or, on it gas is formed and

lightens it in relation to surrounding material. ertical motion begins thro5ing u# chun,s ofdung and bubbles of gas. "ach load dis#laces the last around the circuit round the inner tube.At some stage each and e6ery #article has to #ass a #oint of ma@imum fermentation 5herethe 5hole mass seethes and bubbles furiously. 7# and do5n currents mi@ the contentsthoroughly. (rom there the fermentation slo5s and stratification begins into the layers of gasscum su#ernatant and sludge... the s#ent #ortion of the original solids. Through digestion thissludge 5ill ha6e contracted considerably from the original ra5 state.

(ailure of the bacterial ;bre5; 5ill occur if e@cessi6e loads of manure are used. Gee# to three1$#ound coffee cans daily. If not fed daily for one reason or another and the unit is left5ithout ;food; for a 5ee, for instance start it u# again 5ith four and one$half coffee cans

full the first day and continue as usual after5ards. Do not feed in back coffee cans full foreach missed day *21 cans for / missed days+.

A second reason of failure of the bre5 is an e@cess of 5ater #articularly cold 5ater.

!2. 8emo9ing /cum and *&&luent

(. /cum

1. hen the scum collector container feels hea6y remo6e the filler ca# from the bottom of the scum container and let the scum out.

2. Care must be ta,en that air is not allowed to enter the container at this #oint.

#. *&&luent

3. "ffluent is dra5n off daily or so to the e@tent of a##ro@imately half of 6olume ofdaily in#ut at feeding. The other half of daily in#ut is accounted for as *1+ gas and *2+contraction during fermentation.

4. The su#erior fertili?ing 6alue of the effluent is discussed else5here. This inner tube

digester 5ill #roduce enough to im#ro6e gro5th of #lants on an area of 2 1-2 s:. ft. #er year $$ a good si?ed 6egetable #atch.

!3. /a&et %recautions

%recautions In Gas :sage

!as 5ill burn 5ith a hot flame 5hen ignited as it lea6es the burner *in contact 5ith air+. Butif gas and air are mi@ed together in #ro#ortions of 1 #art in ' to 1 in 1' and then ignited in a


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closed area or container a 6iolent e@#losion 5ill ensue.

To a6oid any #ossibility of e@#losion in this si?ed unit the first time the digester #roducesenough gas to fill the #i#es scum accumulator and storage tan,s this gas should be allo5edto dis#erse to the atmos#here. The second time it fills u# 5ill be relati6ely $$ almost certainly$$ safe to light. The flame is so clean and blue that it 5ill be difficult to see in sunlight but

clearly 6isible at night.The second safety factor is to ,ee# a #ositi6e *ho5e6er slight+ #ressure of gas in the #i#elinesand storage so that air is ne6er dra5n into any #art of the unit. * eights on the storage innertubes #ressure on the main tube 5hen em#tying the scum so the #i#es 5on t colla#se+.

The third safety factor is to chec, the unit daily for lea,sH there 5ill be a discoloration of thetubing in #laces 5here the gas has lea,ed out.

(inally smell is im#ortant in safety handling.

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