Serial: Olade's documents Second Edition No. 11

STRATEGIES ANO TECHNOLOGIES FOR lMPLEMENTING RURAL BIOGAS PROGRAMS IN LATIN AMERICA

Original: English

CDD OLADE

11111~~DJm11111 olade

4.1 Basic Design 4.2 Construction Materials 4.3 Construction Techniques 4.4 Raw Material far Digesters 4.5 Operation of the Digester 4.6 Utilization of the Oigestion Products

4. DIGESTER OF THE llE-MEXJCO TYPE (INSTlTUTE OF ELECTRICAL RESEARCH)

3.1 Basic Design 3.2 Construction Materials 3.3 Construction Techniques 3.4 Raw Materials for Oigesters 3.5 Operation of the Digester 3.6 Utilization of Digester Products 3.7 Comments about the Application of this Technology

3. DIGESTER: XOCHICALLl-MEXICO TYPE

2.1 Basic Design 2.2 Construction Materials 2.3 Construction Techniques 2.4 Raw Materials for Digesters 2.5 Digester Operation 2.6 Utilization of Digester Products

2. DIGESTER: CHINESE TYPE

1.1 Baste Desiqn 1.2 Construction Materials 1.3 Construction Techniques 1.4 Raw Material for the Oigester Process 1.5 Operation of the Digester 1.6 Utilízatíon of the Dígester Products l. 7 Other rnodeís for d rqesters

2. SOCIAL ANO ECONOMIC ASPECTS

3. TECHN 1 CAL ASPECTS

4. GOVERNMENTAL OF NATIONAL ASPECTS

11. DIFFERENT TYPES OF BIOGAS TECHNOLOGY FOR RURAL AREAS IN LATIN AMERICA

1 BIOGAS PLANT: OLADE-GUATEMALA TYPE

a) Energy b} lmprovement of the Agronomic Conditions e) Pollution d) Depredation

1. STRATEGIES FOR IMPLEMENTING RURAL BIOGAS PROGRAMS IN LATIN AMERICA

1. ECOLOG ICAL ASPECTS

TABLE OF CONTENTS

1

The efficiency of this process of bacteria] biodegradation can reach about 80 o/o. With regard to energy, that means a high recovery index among its biological forms that, at present, cause problems: excrements, manure, garbage, aquatic quartz, impoverishment of soils and forests. As can be observed, when this happens it coincides immediately with depollution. Simultaneously, it tranforms such wastes into nutrients so as to assist in improving soils and harvests.

a. Energy

ANAEROBIC DEGRADATION TECHNOLOGY FOR BlOMASS CAN COLLABO~ RATE IN PERMANENTLY ANO SIMULTANEOUSLY RESOLVING THESE PROBLEMS WITHOUT SOPHIMS, ON VERY DIFFERENTE SCALES, ON AN URBAN AND/OR RURAL LEVEL, CONSIDER: .

Without going into a discussion of causes and responsibilities, the truth or falsity on a world scale, it is necessary to analyze the followíng propasa! in order to find a solution:

Energy crisis Food crisis Poltution crisis Depredation crisis

A series of great problems exists in Latin America, and the world over:

1. ECOLOGICAL ASPECTS

l. Ecologícal Aspects 2. Socioeconomic Aspects 3. Technical Aspects 4. Governmental or Natlonal Aspects

A justification of the problem will be put forth the following four basic aspects:

OLADE has surveyed the Latín American region with the object of discerning different opinions with regard to this technology and of learning the relatíve level of progress in research proqrarns or development. The results have demostrated wide diversity of opinions with relation to this theme. There are sorne governments, prívate groups and organizations that have made promissing advances. There are opinions to the contrary that are based, in general, on concepts which do not reflect a real awareness of the possibility of solutíons far many problems, solution facilltiated by the implementation of biogas programs, especially in regions that are marginal to the supply of services rendered by society, as is the particular case of rural Latín American communíties.

Among its programs, the Latín American Energy Organizatíon, OLADE, contemplates the development, promotíon and diffusíon of Biogas technology destined to the rural areas of Latín America.

STRATEGIES FOR IMPlEMENTING RURAL BIOGAS PROGRAMS IN lATIN AMERICA

2

As has been said, the recycling of nutrients (another form in which energy exists} permits substantial soil improvement:

b) lmprovement of the .AaJunomic Conditions

Otherwise, they will only be aerobically consumed in degradation, without being able to contribute to anything more than to poltution. Likewise, the poor people's energy wiil continue being íost and they will encroach upon that of the rich: methanot, hydroelectridty, ethanol, etc., and consequently petroleum and its derivatives.

Sugar cane Seaweeds (algae) Yccat Aquatic quartz

Other crops would be those which produce alcohol, for instance:

Thus, the forests and their fertility may remain in arder to make "energy crops'' through the various non-conventional forms (gasification, leaven, etc.).

a) Energy (firewood and coal) b) Unoccupied times (shepherding, generally excessive) e) Extensive, advancing agriculture.

By substituting the loss of trees with:

By protecting and recovering the plant cover via nutritional improvement ot the soil, deforestation and erosion are reduced, and rapid loss of the hydroelectric resource is avoided not only by depending on electrostatic attraction that fixes clouds but also by substituting water far dirt (sludge).

lt is the only system of energy production that aids in protecting severa! of the other energy sou rces.

lt avoids dead times among the majority of peasants' rural activities (monoculture, shepherding, pasturíng, etc.).

lt doesn't produce expenditures of human energy in dísposing of wastes, nor expenditures of the same when handling low concentrates of agricultura! wastes, in order to improve soils; it recovers, concentrates, fínalízes, localizes and applies these organic fertilizers in the required sites (where more nutrients are extracted through permanent harvests).

lt permits the intensive use of local labor in this construction. lt optimizes rural labor in its operation.

1 t is a decentral ized sou rce of energy and nutrients.

Without d iscussing the concentration (density) of the source, severa! points must be indicated:

3

1t avoids the sophisms that exist in the supposed "treatment" system of sewage and aerobic type garbage, in which energy is spent in "burning up" that which it has.

lt substitutes problems in resources by taking advantage of most of the present and potentiaf pollution, by establishing a basic link between death and the generation of new life: life that is no longer proper to the waste; the breakdown (death) in the digester and the availabílity that ít provides for the new plant and animal life feeds on the previous one.

e) Pollution

Finally, they relieve expenditures, both interna! and externa!: they create bread sources of work by producing, with adequate technology, fertilizers with the additional value of producing energy, instead of expending itas in traditional technology.

The soil and the plants are improved and provide more and better nutrients, at the same time optimizing human and animal diets.

Likewise, it permits intensiva use instead of extensive use of the soil (and water) and polycultivation, which maintains more permanent levels of production and employment thus increasing productivity (not only the mirage of "production") and diversiflcation.

Certain spores, bacterias, etc., are sterilized.

On being nourished in a balanced way (because what is extracted from the soil is not lost), plants become more resístent and productive.

Larvae eggs, which carry plagues (chicken blindness, moths, nematodes, etc.) die; with aerobic fermentation, the destruction of the eggs of nematodes and other is not achieved.

Other compunds are not oxidized and thus destroyed.

Vitamins, hormones, etc. are not burned up in thermophilic reactions, such as the aerobic.

The hormones, micronutrients, etc. are not lixiviaded in non-recoverable liquids,

Volatile Nitrogen is not lost as much due to the fact that it is enclosed as to its low temperature and its ability to mix in organic cornpunds,

Nutrients, fertilizers:

Good pH Moisture retention Settling of degrading micro flora and fauna Anions and cations for disposing of certain nutrients otherwise non+assimilable Protection from inclement weather Long-term nutrients

Organic material for:

Conservation and lmprovement of Soils

e} 1 n a reas with abundant, but unused or underused, waste production (people or cornmunities with the custorn of making cornposts, in order to improve the nutritional condítíon of organic ferti!izers).

d) 1 n agro-productive reqions with degraded soils and problems in their capacity for retaininq nutrients and/or water.

e) In agricultura! reqions whose evironmental pollution (rivers, soil, and air) is oc- casioning living problems.

b) Principallv in regions whose forests are being depredated for these ends and where the residents are beginning to feel a crisis in obtaining this resource.

a) Being the proqrarn on a small scale, with residents from rural areas who require firewood consurnption for cooking their food and who work in agriculture (with the neces- sity of usinq fertilizers, althouqh that may not have been their custom).

As a result, referring to all that previously set forth, from the ecological viewpoint, the most adequeate strategy for implementing hiogas programs is the following:

They are virtually insurance against droughts, given that certain kinds of them perrnit an optimum and scaled use of a water supply.

Not only in rural communities, ata household level (for instance, the Mexican SUTRANE), but also on a grand scale in urban sewage systems (Bremen, Gerrnany: Philippine aquaculture, the U.S.A., the Mexican Dual Ptant, among others), the diqesters have proved to be irreplaceable far treating water and producing energy {including nutrients).

The digesters are an essential in the scheme for the recovery of vital resources such as water and nutrients. lt must be pointed out that in the case of waste water resulting from human use (abuse), a double absurdity exists: we throw out severa! resources with the water and, on doing that, we pollute (a:ttack, kill) rívers, lakes, and seas.

Examples far this particular subtopic have abounded in the pre:eeding ones. lt only rernains to reiterate the general idea of the topic and to point out sorne other examples that emphasize the feasibility ot resource recovery as opposed to depredation. .·

d} Oepredation

By permitting the intensive use of the soil through perpetua! polyculture, plant and animal diversity is increased; and the ecosystem's natural defenses are thereby improved. Thus, since pesticides are not required, there are places far al! the species and bioloqical self-contro! is established (each creature and its predator in a chain).

On increasinq plant resistance, it avoids the abuse of insecticidas, fungicides, etc.

lt avcds the sp rayinq of lixiviated chernical fertilizers on the surface with its consequent disequilioriurn of diets and growth, increase in DBO, etc.

From the point of view of sanitation, the bacteria! content, the viability of eggs, larvae, etc., are considerably reduced, as are the seeds of weeds (which, in a way, pollute crops through excessive proliferation and later through soil abuse due to the breaking of new land and the use of herbicides}.

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h) lnvolve the government or collateral and prívate organisms in arder to guarantee the program's multiplier effect. This effect is achieved by directing thtt communities toward marking their own efforts and constructions, by pointing out necessities and diffusing that technology appropiate for their conditions.

g} Demonstrate the socioeconomic impact of the digesters.

f) Establish real show places in strategic locations whích respond to the solution of common or manifest needs.

e) Train national work teams dedicated to promoting rural development, that can coordinate or organize the interest groups or those who demand service.

d) Support peasant groups so that they will organize productiva activities for the use of dígesters in an integral way.

e) Guarantee simple, direct campaígns to educate and train rural residents, with the idea that, based on their own incentive and interest, they will becorne involved in medium -and long- term particípation.

b) lt is important to detect teaching centers, families, groups and communities that are susceptible to accepting and implementing biogas programs and that have the necessary facilities, organization and support.

a) ln spite of the fact that most people would be considered potential users, attending the necessities of initiating a program of this nature, it becomes necessary to detect an appropiate type of user who guarantees a successful diffusion. Sometimes this kind of person isn't the neediest, but rather he who is more worried helping and serving his com- munity.

Consequently, useful strategies permitting the implantation of national biogas programs in rural areas must consider the following aspects:

The economic aspect of the residents of this region implies limitations, based on the fact that any attitudinal change with regard to their traditions is more easily achieved when the benefits are obtained with low investment costs (with active labor participation) and to improve their living conditions.

Traditional customs among rural inhabitants are very diverse, but in many of these cases it is difficult to convince them to effect radical changes in their traditions, at least if the convi nving is not done by using simple, practica!, and efficient means of demostrating the results,

The social and economic justification for this program is very diverse; but everyone is aware of the basic characteristic of the rural areas of developing countries, princípaUy. Most people in rural areas are dedicated to agricultura! activities, and many of them inhabit isolated, scattered areas without productive resources (among which energy and fertilizer are of great importance}; moreover, their cultural conditíons keep them removed from the soph istícated technologies that perrnit improvements in their standard of living.

2. SOCIAL ANO ECONOMIC ASPECTS

6

f) lt is useful to be aware of the local constructíon materials, soil type, freatic leve!, and avaitable labor.

e) Take into consideration the user's needs, with relation to biogas as well as to biofertilizer.

d) Due to the fact that different kinds of technology exist, with different applications, it becomes useful to diffuse more than eme kind of thechnology in each country, far the purpose of reducing the inappropriate application of technology, which might incite a loss of confidence in thls program, were satisfactory results not obtained.

e) Extend services on all levels, without charge, to the rural areas.

b) Create construction teams that lend support when needed.

a} Develop simple, direct programs which train rural work groups to disseminate the technology (construction, operation and utilization).

Consideríng the aforementíoned aspects, the basic strategies for implementing the initiat phases or program of this nature must take into account the following aspects:

The technology for the operation or management of the plants is equally simple; however, different degrees of difficulty arise with regard to fermenting different raw materials (mainly, plant wastes whose organic compositions have high resin or complex material content).

Nevertheless, in the initial phase [pilot ptants), the construction of the plants requires basic knowledge and materials, possibly difficult to obtain in certain rural areas, especially marginal ones (iron rods, bricks, cement, PVC pipes, etc.). Furthermore, with the object of transmitting basic construction details, it is useful to realize the design with conventional materials; but in any case there is the alternative of realizing any subsequent constructíon with local materials and appropriate technologies. The important thing is to be aware of basic structures.

Biogas technology is, without doubt, almost totally unknown among most Latín American rural inhabitants. However, with the experience obtained so far in smaH--scale, isolated programs, at the moment of seeing the results, the resídents become interested. Such technology is basically adaptable to any cultural and technical Jevel. lt does not require complex aspects nor does it imply dependence on outside economic or technical resources.

3. TECHNICAL ASPECTS

+The government, in the construction of show places -Prívate enterprise, in a cooperative function; and, -1 nstitutions of Community Services, in arder to reinforce traininq and diffusion

programs.

j) Establish the macro-economíc work area with the support of:

i) Estab!ish agreements with users to implement and give continuity to the program. lt is the only means of committíng the user's participation.

7

The fact that programs destined to the rural sector must be channeled through government programs is definitive. Depending on the state structure, the role played by private enterprise and service organizatíons or community groups not linked to the central government becomes very important, Generally, prívate initiative can do very little in the development of programs of this nature in rural areas, mainly because labor, as well as construction materials, are preferably products of the location in question. Nevertheless, within the business sector there will always exist, in sorne cases, a demand far material and equipment that could, through special governmental concessions, guarantee an efficient supply with a reduced profit, with the airn of aiding programs destined to this sector (iron, PVC pipes, water pumps, interna! combustion engines, electric generators, etc.).

The attitudinal diversity among different Latín American governments makes it difficult to sustain common strategies. However, this document makes general proposals with the idea that, according to the nature of development interests in the various countr ies, concrete positions can be contemplated far the support of a program that protects ecology and plant, animal and human health, in addition to freeing the rural area from energy dependency and guaranteeing the production of organic fertilizers in optimum conditions, which directly coincide with the production of more and better foods.

4. GOVERNMENTAL OF NATIONAL ASPECTS

At the national levet, the benefit that the use of this techno!ogy represents will only make itself felt when its implementation is massive. As a resu!t, the follow-up phase is of great importance.

1) The execution of research and development programs on the part of institutions dedícated to this kind of work {institutes far technological research, universities, etc.) is necessary far the purpose of learning about the most irnportant variables of the anaerobic fermentation process and !inking these resu!ts to the biogas pílot plants. This work should have medium-termapplication, avoiding possible duplication of effort.

ln the pi!ot plants, demostration activities will be carr ied out with respect to the ef- ficient use of gas 111 stove and oven burners, larnps for illumination, refrigeration, drying of agricultura! products, stationary motors, etc.

k) Guarantee governmental programs that give continuity to the pilot plants because, otherwise, without having rooted the technology wíthin the daily life of the user, there exists a tendency to abandon the use of the plants, with the consequent devalorization of a program whose benefits do not become observable until its implementation.

j) lt is indispensable that !iquíd, sludge, and/or salid bioferti!izer be used in aqriculture to avoid its accumulation and disuse, again constituting waste, without completíng its cycle.

i) in the initial phase, utilize aspects that simplity the anaerobic digestive process {preferably warm climates, cereal plant wastes, animal wastes, mainly cattle manures, horse manure, and suvine manure) and recur to the use of mixtures, preferably ali those that guarantee rapid fermentation.

h) Keep a conventional record of operational problems that arise on the level of the user. in arder to correct future defects.

g) Elaborate audiovisual material and practica! manuals on the subject.

8

In that regard, it is imperative for governments to begin to evaluate the different sectors in. whích this technology can be used, through the establishment of pilot plants, so that when awareness with regard to renewable and non-conventional energy becomes a neces- sity, they will be able to define their parameters of action, knowing all the limitations regarding the sarne,

lt is almost certain that to the degree that energy problems becomes intensified, sooner or later, this kind of offer wíll have to be integrated into nationaldevelcprnent programs based on the innumerable quílities described prevíously.

e) When the respective Mínistry of Energy does not exist, the formation of National Councils for non-conventional energy sources is also useful, in order to facilitate the action of those international organisms which, like OLAOE; require a link to the dicision+ making power within the governments.

f) lt is recommended that the governments select one of their institutions, to co- ordinate actívities regarding the production and use of biogas at the nationat level; ín ad· dition, this coordinating office will be in charge of gathering and diffusing information on this subject.

g) After these phases, the governments can have a broad visión of the real situation within their own countries, and thus they can define national and international credit policies that guarantee rnassive development of this kind of technology.

d) A relationship between the government and those prívate institutions that may serve as support for the program is recommended.

e) As governments begin to understand the possibilities of this technology, after having established pilot plants, it is useful for them to irnplant national biogas programs, in arder to guarantee success and, furthermore, to coordinate the channeling of actions that a group international organisms or institutions is attempting to develop in Latín Ame- rica.

b) The government, as a directing body, must establish mechanisms to integrate the activity of its different institutions (energy, agriculture, rural development, education, health, and credit) in arder to permit the integral participation of its efforts at action in a program such as this, which includes different fields of action.

a) Consider the participation that OLADE ·can offer in the corresponding energy sector, in its function as a regional organism responsible for the developrnent of this type of programs.

The pr incipaí strategies to be considered ata national leve! are the following:

9

The stage of technological development currently reached with respect to Biogas offers proven solutions for the rural areas of Latin America. The massive experiments carried out by the Chinese, lndians, and others in relation to the adaptation of this highly develop- ed technology for application under the cultural and socio-economic conditions of those regions' rural inbatitants, guarantee its massive success. In addition, Latin America has developed its own technologies suited to its particular conditions.

11. DlfFERENT TYPES OF BIOGAS TECHNOLOGY FOR RURAL AREAS IN LATIN AMERICA

10

OLADE has thought it useful to begin a program reinforced by the participation of experts in the different technologies, articulating the general characteristics of each one. This can serve as a starting point for becoming acquainted with knowledge outsíde the reach of many nations and people already related to, or potentially interested, in the program.

The users of this type of energy (families, communities, small agricultura! holdings) differ greatly with respect to the aspects they desire to obtain from this technology. Besides, if we consider its fundamental impact on the different sectors (energy, agriculture, nutrition, health, ecology, etc.) it is also impossible to critlcize or compare the different technologies. Neither can they be compared in economic terms, since theír impact goes in different directions and is often difficult to evalúate.

Having carried out in-depth analyses of the different types of biogas plants in existence, it has been thought basic to put forth those having the greatest backing with respect to simplicity of operation. Each technology has a different application, In ideal conditions, they are ali highty efficient. The problems arise when a technology is badly utitized, inadequate!y managed and poorly established. There is no universal technique. Neither is there a common need.

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Because the digester is designed far agricultura! use on a large ar small scale, its location should be near a stable or source of raw material. Neverthetess, the gasometer could be located near the place of consurnption, to permit easy observation Of the quantity of gas available.

Location

The tipe of loading and unloadíng of this digester is by batch (discontínuous charge). with dry and salid organic material. That is to say, this activity is competed in one, single operation with discharging taking place until the digestion cycle ends.

loading

Gas-conducting Pipes: The gas circulates from the digester to the gasometer, or from the latter to the consumption lines, through pipes preferably of an anti-corrosive material provided with cut off valves strategically placed at the outlet of the digesters, as well as at the entrance and outlet of the gasometer. Just before enteríng the gasometer, the pipe shoutd have a water-trap, far the condensate and princípally, with a slope convenient for capturing the same.

The gasometer is a cyl1ndrical storage tank, above or below ground, with a diameter similar to its height, and whose size corresponds to the size of the gas-collecting bell, inverted over it. The storage capacity should bedesigned in accordancewiththeconsumption needs; but in general, it is suggested that its volume be equivalent to half of the average daily gas production.

Gasometer:

Dí;esJJ, the diqesters are cylindrical in shape, with a vertical axis and with the height preferably equal to the diameter. Located above---ground, it is on a base, preferably below ground, designed to isolate the digestion chamber from the temperature changes in the ground; this is mainly affected by moisture. The dígester is loaded through the upper part, which has an opening for inspection purposes, with a hydraulic seal. The emptying of the !iquid is done through a drainage pipe placed on the lower lateral part of the digester. The emptying of solids is done through the inspection cover, as well as through a lateral door (built for this purpose) at the bottom of the digester.

form

This plant consists of a set of digesters and a separate gasometer. The reason far having more than one digester is that when one is being loaded or unloaded the other{s) will always be workíng. A gasometer is understood as an inverted bell, which is submerged in a tank of water and which stores, measures and pressurizes the gas in arder to distribute it to the consumption lines.

G eneralities

1.1 BASIC DESIGN

1. BIOGAS PLANT: OLADE-GUATEMALA TYPE

12

units

"

2 3

10 2 3 9 2

2 - Permatex pipes 6 - l" couplers 12 - l" elbows 6 - l" universal joints 4-1" T-joints 12 - l" x 4'' nipples 2 - 1" male plugs

PUMBING BETWEEN DIGESTER ANO GASOMETER

50 ba9s 3.50 m3 2.00 " 1.00 0.50 0.,50 "

55 iron bars 15 kg.

1 70.00 un its 50.00 yd 2 15.00 m2 15.00 kg.

Cement River sand 1/2" and 3/4" gravel

· Boulders Choice material (refractory) Ash (or live lime) 1/4" x 12 m. iron Lashing wire Blocks 0.15 x 0.20 x 0.40 1/2" wire mesh Polyethylene plastic Waterproofind aqent

QUANTITY MATERIAL

MATERIALS LIST FOR CONSTRUCTION OF AN 8.50 m3 OlGESTER IN. FERROCEMENT

lt shculd be mentioned that the safety lirnits contemplated herein can be reduced considcrebly for the purpose of lowering the costs of construction, principally in areas with little seismic risk. The thickness of the walls may be reduced by using PVC pipes instead of galvanized pipes; the covers and the gasometers may be constructed from galvanized plated reinforced with iron, fiberglass, ferrocement or plastic rings, etc. {taking ínto account that one of the gasometer's objectives is to generate consumption pressure, i.e., to supply additional weight in arder to achieve the equivalent pressure).

The materials are calculated for a seismic zone and ferrocement construction.

An example of a small-scale plant is presented below, with two digesters, of 9 m3 each, and a gasometer with a storage capacity of 4.8 m3; ít could be used on a small farm with 10 head of cattle, stabled at night, and proportional volumes of agricultura! waste.

These can vary greatly depending on the availability of local construction material. "Hormígon" (reínforced concrete), bricks and even ferrocement can be used. Also, if construction is to take place in a rural zone very far from a place where iron materials are available, substitutions can be made with bamboo or other hard fibrous plant materials.

1.2 COl\!STRUCTION MATERJALS

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_ b} Water-proofing: it is necessary to make the inside of the diqester impermeable __ in order to stop the seepage of moisture and / or gas through the wal!s; the same goes for the interior of the gasometer's water tank, to prevent water filtrations.

a) Base of the digester: its objective is to impede the direct contact of the digester with the moisture in the ground, in arder to actas thermal lnsulator.

These vary depending on the type of the construction selected. Below are sorne basic aspects:

1.3 CONSTRUCTION TECHNIQUES

10 ba~s 1 m 0.75 m3 8.00 iron bars 3 kg.

150 units

l. Cement 2. River Sand 3. 1/2" and 3/4" gravel 4. 1/4" x 12 m. iron 5. Galvanized wire 6. Blocks 0.15 x 0.20 x 0.40 cm.

GASOMETER SINK

4

5 units l. Sheets 4' x 8' x 1/6" 2. Flat íron strips (or femafe plates)

1 1/2 X 3/16 X 20' We\ding

GASOMETER

2 4

3 units l. Black sheets 4' x 8' x 1/16" 2. lron rods (or female plates)

1 1/2 X 3/16" X -20' 3. Anchor reinforcements Welding

QUANTITY MATERIAL

DIGESTER COVER

y2 91 x 91 cm.

1 5 4 1 1 2 2 2

1 - 1/2" - I " reducer cover 4 - 1" stopcocks 4 - 1" galvanized pipes 1- 1/2" galvanized pipe 1 - 2" gal\fanized pipe 2 - 4" x 12" nipples2 2 - 4" stopcocks 2 - 4" screw - on nipples

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Ilustrations of the construction of the digester and gasholder, wlth the ferrocement technique foliow:

d) Gasorneter: The pressure required to raise the gasholder should not exceed a f5 cm. column o~ w..ter. The water seals for the diqester covers as well as for the water-trap for the conderisate equal 30 cm. which provides an ample margin of safety. Nevertheless, it is very important to avoid any friction in the free movement of the bell, which would impede its displacement, with possibility of increasing the internal pressure of the digesters; (in extreme r:-ases) this could cause cracks in the construction. In case the cover of the gasho;der is .ict hc.;;c:vy enouuh to provide sufficíent consumption pressure, this can be aided with heavy rnaterials such as stone, bricks, etc., untif the required pressure is attained.

e) Other details: the pipe for conducting the gases. lt is very important that the parts joined to the valves, nipples, etc., be perfectly and hermetically sealed to prevent any leakaqe thz' could interfere with the proper functioníng of the digester through loss of pressure.

This imperrneability can be achieved with different types of materials, depending on their local availability, but it is essential that they fulfill their porpose.

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When the digester is to be loaded with only one kind of material, the operation should done in layer 30 cm. thick, successively compacted. When the load is comprised by a

of materia!s to be deposited.

The loading of the digester begins this phase. The material to be used should have been previously composted in the open air for ten or fifteen days, a process which besides allowing far an easy beginning to the digestion process, reduces the humidity contained in the fresh material. This action is necessary (although not essential) to facílitate the compaction of the material ínside the digester befare it is completely filled.

1.5 OPERATiON OF THE DIGESTER

The animal manure should not be less than 1/3 of the volume, which can be augmented with plants having a low content of organíc matter and high levels of cellulose. lt is also useful to consider the addition of mineral nitrogen, urea, to aid in providing the nitrogen required by the bacteria in order to function in this environment.

A digester has been operated efficient!y with the use of residue from grain crops (corn, rice and wheat); sugar cane bagasse; p..llp or husks from coffee, aquatic plants; waste from bananas, tabacco, and beans; animal manure in general; and composted organic waste.

The materials used in th is technology of low dilution (40 to 60 o/o solids in soiution, depending on the density of the material) vary greatly. With this system it is possible to digest methanogenical!y with sorne variation-materials not easily digested with techniques of high dilution and continuous or serm+continuous load. Preferably, animal waste is mixed with waste to obtain an appropriate ratio of carbon/nítrogen, ín order to achieve a bio-fertilizer of superior organic characteristics.

L4 RAW MATERIAL FOR THE DIGESTER PROCESS

IOIGESTER 1 SCALE. 1: 20 A- 1 DE TAi L

oontoins: 11 oolct: PLANT-OETAIL INÍ>1CATEO

oopaclty: 1 lf pe: EACH DIO.: 9 M3 OLADE-GUATEMALA )~·--------------·-·•~~~~ .,,u~•---~-="""""""--~

PLAT E (PLANT BASE) SCALE. 1:20

projoot: l"ERROCEMENT CONSTRUCTION DETAIL

REIN FORCEMENT IRON ola de

1 1 .. .. , . 3 o '1

DIETAIL A·l

.~o

.40

.12

,40

·'ªI .30 .ID

1/4" IRON BAR 1/4" IRON BAR ALTERNATEO AT ,30

1 ALTERNATED AT . 30 l

.ti o <;} 111 1/4" IRON BAR AL TERNATED AT • 30 +· ·+

A A' 2.85

2.54 2.42

1/4" IRON BAR ALTERNATEO AT .30

l. o 8

2 sool•:

INDICATED oontaina:

SECTION oapaclty: t11p11; EACH 018.: 9 M5 OLADE-9UATEMALA

PL ATE

pro)oot: l'"IERAOCEMENT CONSTRUCTION DITAIL

e o QJ BLOCK l'"OR CIRCULAR FORN .18 JI .20 JI, 40

5" STOPCOCK

2.00

UNIVERSAL JOINT

1/2" TEE

1/2" PLUG .36

l •O I/>" 6ALV. PIPE

A-Aª SCALE. 1 20 S ECTION

LEVEL ".12

a" 8ALV. PIPE

1 1 ~

8AS OUTLl!.T

1" El&OW · .o

I" 8ALV. PIPIE

H V DRAUL.IC SIEAL L.IEVEL + 2.48

.11 l. 1 6 ~----~--·----·-··-------1'- 4" /º.r .f-----·-··-~-.!..: 05 _ .06 .06 __ .,.._~

METAL.Lle COVEFI

IJIVEL !.0.00

11!.00

.06

.80

.ae

3 o onta In•:

SECTION fl LATE

projoot: Fll'UtOCIMl!NT CONSTRUCTION Di TAIL

a - A e "' SCALE. 1: 20 SECTION ola de

~ ~ 1 "' • 40 -r.lfJ 'l

.. • 97 J. '1 '1

1.10

l. 1 8

1.27

,so

STONES

.20 .20

• 16

.05 .32

POI.. ve:nrtL.IU4E .40 MATERIAL

CIRCULAR FORM LEVEL. ... 12 .15 11,20 a. 40 RE TIC LE

oepoolt)I; typo: IACH Die. : 9 Mii OL.ADE-8UATltNAl.A

.oalo: 1 NDICATE D

(CONTI NU ATION)

lltVlil. %0.00

1/4" RETICLE AT .30

.15 11. 20 11. 40 BLOCK

4 PI- AT I! 9001•: contoln•:

PERSPECTIVI!

"'ERROCEMIENT CONSTRUCTION pro!eot: r O! TA t L

QI otade

. type: oopciolt: .. 9 Ma OLADIE·GUATEMAl-A IEACH 01 ... ·

p E R S p E C T 1 V E-· DI GESTE R

OUTLET

···---::; .. ::~~:..~ .. , .,

~..,.,,../-

HYDRAULIC SEAL

5" GALV. PI PE

I" 9ALV. PIPE

GAS OUTLET LEVEL FOR

1/2" GALV. PIPE

HYDRAULIC SEAL

oopoolty: ty pe: 8 M!I GASOMETER OLADE·GUATIEMALA 5

soalo: lMDICATED

PL AT l contolns: PLANT

projoot: FEflAOCEMENT CONST RUC TI o N OITAI L

olade

GAS INLET ANO OUTLET

METAL BELL

.15 11. .20 x .40 BLOCK

GEN ERAL PLAN T SCALE. 1: 25

( VIEW OF SINK WITH BELL)

GASOMETER

B •

I'' GALV. PI PE

~ - - - -· --· -· ---~~~~~~=-=----~ 1 e'

1.44 1.29 1.26 1.16

aon tains; SECTION

1cal•: lNDICATED

proJoot: FER ROCl:MENT e ONSTRUCTION DETAil

P L AT i! 20

olade

-+ CONCRETE GUIOE

l. 615

oopocity: type: 5 MS &ASOMl!:TE OL.ADE·GUATEMALA 6

SCALE. 1

l. 63

B- B'

1 1/2' GAL.VANIZEO PIPE

2" Q LVANI ZED PIPE

SECTION

GAS INLET ANO OUT LE T

1" GALVANIZED PIPE

1.12 1.22 MORTAR WALL PLASTERED WITH

.16 K .20 11 -40 BLOCK

,10

.1 o

1 1

LEVEL ! 0.00 +- -

1 1

1/16" BLACK PLATE

1/4" REINfORCEMENT

~ -··~·~···· -./'-

.. ·-t- l. 1 6

4 1 1 1 I• ~ 11

1

1. 1 l 1

l. 2 6 .¡. ... l. 2 g

l. .. 4

type: OL.ADE • 6UAT 1: MAi. A

oc¡pool ty: 7 IN D ICATEO DETAll.S

P L. ATE oontQlns: •oale:

prohot: F ERROCEM ENT CONSTRUCTlON DETAil.

ola de

SCALE. 1: 1 O

WATER SEAL DE TAi L

.os

.30

PERSPECTIVE

PIPING DETAIL ( INTERCONNECTION BETWIEEN DIGESTERS)

PLANT

METALLIC COVER SEAL 'HYDRAULIC DIGESTER DIG ESTER

PIPING. DETAil ( GASOMETER ACCESS)

PERSPECTIVE OETAI l OF CONDENSATION

WATER TRAP

PLANT

.30

PERSPECTIVE

GASOMETER

23

The design of the digester with a metal tap of the same size as the diam eter of the cylinder can be changed by taps of smaller diameter and cost. Their size will depend on the easiness of unloading the digester from inside, by suing a shovel.

Chart No. 8 shows in detail this model of digester. The material needed for this digester has small changes in regards to quantities. The material and cost of the metal tap is reduced enough. In the chart one can see designs A and B for both types of reduction of the neck that have been recommended.

1.7 OTHER MODELS FOR DIGESTERS

The most important objective of this technology is the production of a large quantity of bio-fertilizer with high organic content, which is very reliable for the reduction of eggs and other elements harmful for human as well as for the soil. To demonstrate this, the example of the plant described above can be used: its volumen of production corresponds to six tons of salid bio-fertilizer, and 4 m3 of liquid bio+fertilizer, in every discharge, and a máximum daily biogas production of 10 m3 (depending on the conditions of the mixture and the environment).

1.6 UTILIZATION OF THE DIGESTER PRODUCTS

The gas outlet valve on thís digester should be closed, and the water seal should be emptied. After this, the digester should be u~covered and the drain-pipe opened to a!low the líquid bio-fertilizer to scape, leaving it to drain completely; this process takes ap- proximately 48 hours. At the end of thisprocess the salid tertilizer is extracted and the digester is cleaned, so as to be ready to be loaded once again.

The period of digestion, given adequate mixtures and suitable climatic conditions, can take approximately 35-45 days, with useful outputs of gas.

On observing a decrease in gas produch~p (when this reaches levels which are not very useful), it is time to begin the discharge pn:/cess.

Under favorable environmental conditions, the production of gas fuel is noted between 4-1- days after the sealing of the digester.

After this, the dlgester is closed and hermetically sealed, with water added to the respective seal .. The digestion process now begins.

lt is also important to mention that befare sealing the digester, one should wait for the water to seep into the material, in arder to avoid unexpected drops in the level of water situation which is quite undesirable.

Once filled, the digester is saturated with water (or preferably, with residual liquid from previous loads} to a leve! sorne 10 cm. above the level of solids.

The required compactíon permits the elimination of air bubbles that may remain inside and at the same time increases the digester's capacity for receiving solids.

copoclty: 9 M~ 8

DETAILS •cale:

INDICATl!D p L ATE con taina:

project: MOOlflCATION ACCEH MOUTH IN fERROCEMl!NT

OJ olade

typo: OLAOl!·GUATEMA

e

N +O.ID

···- -~-· -~..._2_1 ----- . -.t- R • l. e e ······--·· - . ·--~-~~-·-·- t-

i 1

1

1

¡

f·--

-.t---- --f-- o. a o

S CAL E. 1: 25 SCALE. 1:25

DESIGN A DESIGN

N • 0.10

2.00

N '!' 0.00

R• 1.26 ····-··-------~ ···--···~t 1

1

1

1

1 1

1

-· . -~-~- .C>.'. 8..~. - ·--4- R •O. T 2 . . ----·- ·····- --··· ----··-----r-- 0.30

0.65

N 1' 0.00 ---------·--·

1.85

0.20

0.30

9 1: 25 ESCALA

LAMINA CORTE oontlen• · COR re:

••cala: 1 NDICAOA

proyecto: WODlf'ICACION CON GASOMI!: J" RO INCORPORADO S081'1(! OIGi:STOi'l

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oapacldad: 9 11!'!!.

.40

Ji . .40ii .60

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111" 0.00

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111 • .12

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VARILLA oe: HIERRO llJ l/ 4"

a 0.16 AL T !!:PINADOS

TUBO GALVANIZADO tfJ 2"

.00

MALLA DE ALAMBRE: d 1 lll!l"

TUBO GALVANIZADO ----. -~-·---·-·---------,·----------

,03

CAMPANA ME TAU CA

.Ofl .01! ~ ,(- .f -{

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1 2.01 .oe .oe ,¡...¡. . .¡.. f

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2. 47

25

Digesters, of 50 m3 or larger, also require quarter-inch thick iron rods (wire) to strengthen the dome-wall joint ring. They also require pre-fabricated concrete piping, 25-30 cm. in díameter, far the inlet pipe and the joint between the ferrnentation chamber and the effluent outlet.

a. prefabricated concrete blocks and mortar b. Baked clay bricks and mortar c. bricks made of "puzzolanic cement" (lime-puzzola) d. boulders and mortar e. ordinary concrete (cement, sand, grave!) f. dírectpit excavation in rocky terrain

The digester can be constructed with diverse materials, depending on the nature of the terrain, the freatíc leve! and avaílab!e local materials:

2.2 CONSTRUCTION MATERIALS

The gas storage takes place inside, in a free space determined far that end.

The demand far biogas and fertilizer, along with the avai!able organic waste material, will determine the capacity of the Chinese-type digester to be constructed. lt is particu1arly adaptabie to family sizes (interna! volumes of 6, 8, 10 or 12 m3} although the community sízes (interna! volumes of 50, 100 or 200 m3) have been widely accepted. This design can be adapted to varied climates, including temperate and cold ones, because of its great capacity far thermal insulation, which reduces the effect of temperature variations between the seasonsand between day and night.

The combination of these characteristics creates a highly resistant structure which uses fewer construction materiales far a given interna! volume and which can be constructed with local materials at reduced costs.

a. There are no movable parts b. Circular section, vertical axis: cylindrical walls c. Flat: srnall height/diameter ratio d. Dorne+shaped roof and floor: spherical sections e. Underground construction: buríed f. Lateral intake and outlet charnbers: diamet:rically opposed g. Removable cover in the upper part of the dome with an opening far the gas out!et

pipe

The Chinese-type anaerobic digester uses semi+contmuous operation and has the following design characteristics:

2.1 BASIC DESIGN

2. DIGESTER: THE CHINESE TYPE

26

In the first place, the pre-fabricated concrete blocks are fabricated manually or semi- industrially using molds suited to the size of the digester and each of its parts (wall-dome). Then an excavation is made far the wall, until its proportions are those of the desired diameter and depth, plus an extra space around it which will later be filled with cornpacted earth. After putting regular-sized boulders on the earth floor, which was previously corn- pacted, concrete is poured to form the base of the digester, making use of special wooden frarning for each size. lmrrediately afterwards, a cylindrical wall is put up, row by row, filling in the extra space with well-compacted earth. Once the required height is reached, a ring of blocks is constructed to support the dome; the circular wedge wilt be filled with mortar (in the case of community digesters, this wedge will be reinfurced with 1/4" iron rcds). The dome construction can be made with a bamboo form and woven straw mats or partically without the rnold, but usíng iron clamps for support. This type of construction is the fastest and is recommended for terrain that has a relatively high freatic leve!.

a. Construction witlt Pre-fabricated Blocks

We will refer to only three of them:

2.3 CONSTRUCTION TECHNHlUES

1.300 units 29 units 22 " 4 m3 2 m3 2 units 1 unit 3 units 2 "

20 kg. 10 ft. 18 ft.

3 1/2' 3 1/4"

1 unit 1 4 ft. 1 unit 5 units

50 ft. 8 pounds 3 units

10 units 1 unit 2 units

l. Bricks 2 x 4 x 8" 2. Porttand cement (45 kg. bags) 3. Lime {22 kg. bags) 4. Sand (fine grain) 5. Grave! of 1/2" 6. Cement pipes 10" x 3' 7. Cement pipes 8" x 3' 8. Boards 1 x 4" x 10' 9. Bcards 4 :< 6'' x 12'

10. \Vater proofing agent 11. PVC pipes of 1/2" 12. PVC pipes of 1 1/2" 13. PVC pipes of 2" 14. Chain of 1/8" 15. Playwood sheets 16. Stopcock 1.2" 17. Cooper tubing of 1.2" 18. Galvanized tee of 1/2" (union) 19. Fittings (ring-mounthed reduction couplers) 20. Hose of 1/2" 21. Trail rope 22. Plastic kegs 23. Ctamps of electric wiring of wall 24. Joint sea!ing tube (permatex) 25. Wire mesh of 1/4" x 12 m.

0.UANTITY

CONSTRUCTIOrd MATERIALS USED IN THE CHINESE-TYPE BIOGAS PLANT 12 ml WITH BRICK TECHNIQUE

MATERIALS

27

-The bricks to be utilized must be wet (by imrnersion} two days befare, but at the moment of use must be superflcially dry.

-Place a compact layer of stone, befare forging the base (to have a 90 o/o protectíon) then place a small bed of stones, with a thickness of sorne 0.10 to 0.15 cm. Wet the ground with the compaction.

-The digesters made of bricks and blocks require 6 interna] coats of plaster, as a sealing agent to prevent leakage. The dígesters of molded concrete need only one coat of rnortar mixed with sodium silicate.

-The intake and outlet chambers are contructed from bricks, blocks, or moldee! concrete.

-The inlet pipe and that which unites the tank and outlet chamber are always installed before the wall is completed and befare the dome is constructed.

-The collar or mouth of the dome is always constructed with a frame made of wood or another material.

d. Notes 011 Constmction Technlques

This construction techniques requires special skill, which, once acquired, allows for the bulding of the most economical digesters, in terms of economy of materiafs and labor. lt is recommended fer consistent soils and low freatic levels.

First, the land is marked out with lime by means of a projection from the upper plane of the digester. Next, a hole approximately 60 cm. in diameter, and 2 meters deep at its central axis, is excavated. Then, a partial excavation of the earth is made until it reaches a depth profile exactly equal to the inner part of the dome, this being achieved by shaping the land with the help of special molds. Afterwards, excavation of a circular trench is made, sufficiently thick and deep to form the frame of the wall with earth. Concrete is poured into the trench in 20 cm layers, compressing frequently in order to eliminate air and water untif the walf is completed, Then, concrete is poured on the earthen dome following the thickness of mold and proceeding radially to complete the dome. As soon as the dome and the wall are formed, and this takes a mínimum of eight days, a masen goes into the central opening and gradually removes the earth from the middle in a circular manner from top to bottom, until he reaches the desired depth; pours in concrete, wlth the help of another special mold. The material taken out is used as filler spread over the dome.

c. Constmction with Premixsd Concrete Using an Earthan Frame

Construction is similar to the previous case, up to the pouring of the floor; then the wall is constructed wTih four'rows of bricks (In the case of the famiTy---size digester}. The support ring for the dome is similar to the previous case, except that it is made with bricks, and the dome is constructed without the need for .a grame, using iron clamps far support. This, being the simplest technique, is slow and is recornmended for terrain that has a low freatic leve!.

b. Construction with Bricks.

28

PROPORTIONAL CHART OF MIXTURES ANO MORTARS

Mixture Thickness Cernent Lime Lime Coal Regular Fine Clay Sodium Ferrous Calcicum Paste Ashes Sand Sand Paste Silicate Chloride Chloride

Base 6cm 1/2 3 2 o/o Mortar 2cm 1.5 S.5 2 o/o Whitewash 3 4

.e 1 5 mm 20 o/o 2 ojo .. "' 2 7 mm 2 3 ~ " ...

3 5 mm 2 o/o :E ~ 4 4mm 2 2 3 2 o/o ;;¡ e 5 5 mm 20 o/o 2 o/o ... .. .....

6 film 2 o/o 200/0 .5

-The inside face of each brick must be in strong, direct contact with the next brick. Fill the rest completely with mortar mix and with sorne little stone pieces, to obtain better pressure.

-The size cf the sand particle has to be smaller than 0.35 mm.

-To determine ·the shell form, use: 1 central axis and a cord to mark the radius of the shell or of the cylinder (with a leve!).

+The first two rows of the coitar should be formed from brick halves, placed verticaily.

-The tube to the inlet chamber should be covered with 3 applications of pure cement paste, to be brushed on.

-The slope of the base of the upper dome is extended (with string), with the radius to the last bi ick of the cylinder.

+Lirne paste: 3 days before use, put lime in 3(r-40 o/o water and grind; 24 hours later, sift it through 1 mm. mesh. Protect with plastic from excesses of water and sun.

29

The Chinese-type digester uses all types of agricultura! waste, includíng human excretion, while it is always recommended that a mixture of materials be used, The Chinase operation techniques permit the digestion of cetlulose material, e.q., grain residues, grass, leaves, etc., as long as the d igester is loaded with material that has been aerobícal ly pre- composted. The techniques of pre-compost is described in a subsequent diagram. lt is important to emphasize that a !arge degree of the success of the Chinese biogas technology deper.ds on pre-compost, and the following advantage are to be derived:

2.4 RAW MATERIALS FOR DIGESTERS

t ypo: CHINESIE

011poo1t1: 12 M3

oon toi n1: PLANT 1

SCALE. PLANT 'ºª'º:

trCDl_CATED

projeot: 810· 6AS Dl6ESTER WITH MUO BAICkS

P L ATE 33 1/3 GENERAL

3.50

- ~-- --

--.!" ---- ··-~·

1.14

2.25 - -+

l. 7 5 +----- --------- -- ---- --- -------------.!'------------- -· ·- ----------------.¡------- ------------· ······------.r- ---- --------- . 94 .eo . ss 1. 20

-->t· -·- ------------ -------------------------------- ---------------------- !!L 04

-- -- - f ·

/ I ¡ I

¡ I // 1/

DIGESTER ENTRANCE / AND WATER SEAL / 1

/ I / /

"' 1 //:// ,, ,,.. / ....................... ..,., /

......... - . - .,,,,.., ..._...::::- --t- --- ::. _..,, ---t---- •

INTAKE CHAMBER

OUTLET CHAMBER

---,-- ....... »>: __ , ............ ....- ..,..,..-- ..._-.. ....... .,,,., ,,,- ......... ,.......,,, .......

/ / . ....... ~/ - 1 '~, '' ',,

\'\ \\ \\ \\ \\ ,, \\ \ \ 1 \

OIGESTER DOME OF MUO BRICKS AND FINE PLASTER

e• O-·+·...;.> e'

OJ olade

P L AT f oontolns: 1ca!e:

2 SECTJON INDICATED

oapaolty: tJ pe: 12 MS CHINl!:SE

SCALE. r : 33 1/3 SECTION A- A 0 project: 810·9AS Oltll!:8TER IN MUO

l!I RICICS

OJ otade ········----·-···-----·-·-··-------···----·-- ··---------------·--f-···- . ··--f-------······----·----.;- .... ,r ......

"5. 00 . 30 . 90 • 06 --.!'-···-·-- ---····· ····--.'/"-ir-·----·-·····-·- .

.64 .'06

·ª~····· .. _,f.

\ \ \

\ \

1 1

OUT LE T . 42 1

. . 1 . 30 1 1

s a t_· t .06 ·ti· 44 .. .20

l. 21 BIOMASS INLIET PIPE

2.79 1 \A• 3.18 \ \ \ \ \ \ \ \ \

1 \ R•2.38

\ \ \ \ \ 1 \ \

I I

I /

INTAKI! CHAMBER \ \

1 \

.45

_.05 ..

.35

,29

1.58 .50

OUTLET CHAMBER

+--------· 1 FILLER j\

1

2.25 .06

.06 1. 2 575 .12 .06 . 9 o -----.~,._·.....,~-----··-·-·

.06

,06 .70 .06 .9775 ,605 tt------~-.."#---·---------·~-.........;.-- ·-t---

.06 1. 715 L

P LATE oontaln1: BOQI• '.

3 SECTION • DETAILS INDICATED oqpaolty; f)'p•:

12 M! CHINESE

projoot: lillO·GIAS Dl8ESTER WITH MUO llRICKS

ola de

ELEVATION SCALE. 1: 10

SCALE.

.46

331/5 SECTION

CONCRETE COVER .05

.05

PLANT SCALE. 1 10

.01

.14

-·~ ~---:--&ó .. DIGESTl!:R BASE WITH PACKED

EARTH ANO SMALL STONES

.14

DETAil B-5

!llUD BRICKS · CYLINDER WALL WITH

DETAil 8·5

PLASTUiED ANO

---- ?'~ /

I , 1 1 \ x ' ' /

:---..... _

COLLAR ANO WATER SEAL

.08 1.02 .06 -~"iªL"'-fft, ·-·----------.-~-.~~--.,l<Ja--

.os 1.0 2 .o e . ao --#----··--·-········-#···-·-···-·--··· t

¡·

REFI NEO COVER

.01

., DETA!L COVER

. 30

5. ,2 ~- ··--------·~- ----···----+

1 ' 1

i 1 ·58

+.os~ .oa .20

1.21

279 2.09

.ao

.26

.64 .34

4 SCALE. t:IO PLANT type: CHINE.SE

S!CTION· DETAil 1 NO 1 C ATE D

oopoolty: 12 M5

eoole:

projeot: BIO·EIA8 01Cilllt8Tltfl WITH MUO BRICKS

P L ATE oontolns:

ola de OJ . SCALE. 1 : 331/3 e - c ' SECTION

1 .58 1

.06--' .20 t

1.21

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-./'---. -- . 8 o --- - ----.¡.

/ / /

/

.14

1

1. 40

ELEVATION SCALE. 1: 10

-~ »I --:tt,f-· . 5 8 ·-·--~

-·-4'#···--·--·----···--·-·------·--- ··---·-~- .or .66 .01

~O!'INi;:cr ~ 5/J/," Pl,.ASTIC >lOSIE

TO GAS OUTLET PIPE-

JI) i/~" u /tii" IFION

IUNDLE

ABOVE THE DOME, VHH<m WIU. Bt: PLAST!!RED BEFOAll! l'"ILUN~

2.79

.64

.46

THE FILLER WILL BE CFi\11-'~CTIED

.14

1051 .12 07

DETAil COVER

.20

.40

.04

1 • L .04

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.681 ¡

1 t·º' .16¡:~

,,,.: CNINIEU'. 5

P&'fAILI •••lo: INDICATID

P l. ATE oontQIH:

proJect: 810· 8AI DltE ITIR 1 N MUD 8RICK9

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I I I

I 1 R• 2.18 I I I

COMPACTED FILLER

LIME MORTAR SEAL

COLLAR OF COMPACTED BRICK

MORTA R

.. .. ~ .16 .. ..

SCALE. 1: 10 A- 3 DETAil

.64

SCALE. 1: 10 B-3 DETAil

\ \ 1 \ \ftn 3. IS

1 \

BASE MORTAR

IS lAY!ERS OF PLASTIERING AND WATER· PROOFIN6

I I

I I /R" 2.38

I I

/ / PIORTAR

PLASTERIMG IN DOME WITH COíVIPACIEi> FILLE~ ABOV!!

35

The effluent should be collected simultaneously with the periodic loading, to be used in agriculture livestock activities or for aquaculture. Every 6 months, more or less, the Chinese digester should be emptied to collect the sedimentary sludge and liquid effluent, leaving a tenth of the initial volume of the latter in the digester, asan innoculator far the new load.

The gas is carried by plastic pipes directly to stoves, larnos, motors, and other combustion devices. This design does not allow the user to obtain biogas at a constant pressure; thus, it is recommended that the consumption of this gas be regular, in order to avoid great fluctuations in the pressure.

2.6 UTILIZATION OF DIGESTER PRODUCTS

The Chínese-type digester functions on a semí+contmous basis. lt is initia11y loaded with pre-composted material at a concentration level of 7-5 ojo of the total of solíds in suspension and, then it is reloaded periodically (daily, every other day, or weekly) with raw materials, preferably precornposted, in a quantity equivalent to the gas produced. lt is recommended that the liquid effluent be recirculated frequently.

2.5 DIGESTER OPERATION

f. obtaining of more homogenous and accessible eff!uents and sludge. Moreover, it is very lmportant fo add different types of inoculares in the initial load, up to a voiume of 10 o/o of the total volume of liquid.

e. partia! degrading of the initial raw material, which accelerates the production of biogas tuel,

d. heat that raises the temperature of the initial solution of the loas.

c. heat that is responsible far destroying the majority of parasites which are initially present.

b. generation of heat (60--70ºC) that removes the waxy coating of the straw and permits partial cellulose and lignine breakdown untíl their homogeneous disintegration in the digesting 1 iquid, avoiding the formation of foamy scurn,

a. adequate temperature for the multiplication of aerobic and anaerobic bacteria.

~ MIXTURE OF THE PILE UP MATERIAL

1111 SPRINKEL WITH LIME WATER 2 %

• OIGIESTIER NUTRITION COVER THi. CATTLE WITH so K@. OF FRESH 1'4ANURE

• RESTING DAYS 1%1 MATERIALS. SELECTION

- CHAP OF THE FIBROUS MATERIAL = PILE UP OF THE MANUR[ ANO STRAW

D A y s o t 2 3 4 5 6 1 8 9 10 ti 12 13 i4 15 16 17 18 l9 20 21

~ = • ~ • • • • • • • rB • ~ = • • • ~ • ~ • • •

~

~

[:]] • • • • mi • • •

PREFERMENTATION CHRONOGRAM

37

AVAILABLE INFORMATION COLOMBIA JAMAICA GUATEMALA ** PERU

Entity "Providence" Experi- Scientific Rearch CEMAT IT!NTEC mental Farm Council

Person in charge J. Correa Bulla K.C. Lee R. Cáceres J. Verastegui Numoor of digesters under ronstructlon 9 3 síze of djgester ( m3) 12 67 12 10 Location Bogotá Kingston Platean Plateau Environmental temperature 12-27 22-28 10-22 10-18 Altitude (m/sea Ievel] 2.600 100 1600-2000 1600-4000 Construction technique Concrete Prefabricated Puzzolanic brick Molded concreted

block

Biogas production 3m3 f day 150 m3* 2-4 hr/day 2-3m3 ¡ day lnitlal raw material manure Composted Pre-composted Pre-composted

Chicken-manure manure and straw manure and straw Periodk raw material manure Chicken manure Fresh human Fresh sheep

water feces Cornpost manure and water

Biogas uses cooking cooking Cooking and illumi- Cooking and illumi- nation nation

Effhient uses agriculture agrículture agriculture agricul ture Slude uses agriculture agriculture agrlculture agrículture Sanitation date l 0-4 coliforms/ml 95 o/o death rate

500 viable eggs among parasltes

* Estimated or expected data ** OLA DE built one digester similar to those descríbed, which total 1 O.

KNOWN LATINAMERIC:AN EXPERIMENTS WITH CHINESE TYPE DIGESTERS WITH DOMES, AS OF JUNE 1980

38

In any case, the use of local construction materials, such as compacted earth, brick, stone or ferrocement, is recommended, in order to keep down costs,

use. This type of digester can be built on a small family scale or on a large scale for industrial

We use as examples a digester with a 16 m3 capacity another with a 12 m3 capacity, which respectively, can process the manure from five and eight dairy cows kept in a barn. The íormer produces between 8 and 12 m3 of biogas per day, and the latter, between 4 and 8 m3.

Any type of material can be used, but low+cost ferrocement is recommended. The versatility of the system means that the digester can be built by the users themselves.

3.2 CONSTRUCT!ON MATERIALS

Near the source of the raw material, preferably below the stable or beds of the contributing anímals. The topography of the terrain may vary becuase of the nature of the project.

Loeatien

Continuous or serni+continuous loading. Discharge at short or long intervals, as convenient.

Operation

The construction of the gasometer is similar to that described for the OLADE-Guate- mala type biogas plant, with a gasholder made from 26 gauge galvanized metal, protected by anti+rust paint and interconnective polyethylene piping; although a gasometer iarger than one described in subsequent pages is preferable, in arder to avoid the entry of excess pressurs dueto gas accumulation.

The digester is an uderground rectangular, horizontal pit with a separate gasometer. lt is loaded through one end and the liquid effluent and digester sludge are discharged through the opposite end. There are 4 outlets at this end: biogas, solid and foamy scum, liquid bio+tertülzer. and serni+l iquid bio-fertilízer in the form of sludge.

Genera!ities

3.1 BASIC DESIGN

3. DIGESTER: XOCHICALU-MEXICO TYPE

11 bags of . 45 kg.

1.5 m3 0.5 m3 5 units 2 kg.

450 units 1 unit

QUANTITY

30 bags of 45 kg.

3.5 m3 1.0 m3

15 kg. 3 ro lis

(120 m2) 2 units 3 units

10 units 2 units 3 units 4 units 3 units 8 units 1 unit 1 unit 1 unit 1 unit

35 units 15 kg. 14 pieces

1 piece

39

23. River sand 23. Grave! 25. Wire mesh of 1/4" x 12 m. 26. Tie wire 27. Bricks 2" x 4" x 8" 28. Gasholder (according to the design)

22. Cement

GASOMETER SINK

6. Cement pipes 10" x 3' 7. PVC pipes 1/2" x 5 m. 8. Elbows 1/2" 9. Universal unions 1/2"

10. Couplers 1/2" 11. Stopcock 1/2" 12. Tees of 1/2" 13. Nípples.of 1/2" x 3" 14. Nipples of 4" x 10" 15. Níppíes of 2" x 10" 16. Stopcock 2" 17. Stopcock 4" 18. Wire mesh of 1/4" x 12 m. 19. Water proofing agent 20. Wood boards of 3/4" x 6" x 6' 21. Rectangle shaped scum gate of the meta 1 pi ate of 1/8" mou nted

on an iron angle frame of 1-1/2 x 1-1/2 x 1/8" with screws and knobs incorporated. Of 0.30 x 0.60 m. (wíth rubber gasket}

2. Ríver sand 3. Grave! (approximately l" diameter} 4. Tie wire 5. Chicken wire

l. Cement

MATERIALS

LIST OF MATERIALS FOR THE OLADE-XOCHICALL Y-MEXICO TYPE DIGESTER OF 16 m3

40

a. Site Selection: b. Calculation, choice of size of plant (s), and outline; c. Technique to be used; d. 1 Excavation and assembly

11 Cutting and assembling tank (if it is of ferrocement but no .larger than 20 m3) and excavation of the sarne:

e. Casting, etc., of base and walls;

Phases:

We will cite a typical case and point out the options:

There is an infinite number of variations, adaptable to conditions of site, sub+soit, topography, climate, use, materia Is, labor, etc.

3,3 CONSTRUC:TION TECHNIQUES

2. River sand 3. Grave! 4. Tie wire 5. Chicken wire (3/4") 6. Cement pipes 10" x 3' /. L;: .... ,¿Leo polyethylene 8. V1fae .nesh of 1/4" x 12 m. 9. PVC pipes 1/2" x 5m.

10. Elbows 1/2" 11. Universal union 1/2" 12. Couplers 1/2" 13. Stopcock 1/2" 14. Tees of 1/2" 15. Nipples of 1/2" x 3" 16. Nipples of4" x 10" 17. Ntpples of 2" X 10" 18. Stopcock 4" 19. Stopcock 2" 20. Wood boards of 3/4" x 6" x 6' 21. Waterproofing agent 22. Rectangte shaped scurn gate of the metal plate of 1/8" mounted

on an iron angle frame of 1-1/2 x 1-1/2 x 1/8" with incorporated knobs and screws. Of 0.30 x 0.60 m. (with rubber gasket)

23. Double gasometer with galvanized platear fyberglas polyester resin of 1.5 m3 capacity

l. Cernent

llUANTITY

23 bags 45 kg.

2.5 m3 1.0 m3

15 kg. 86 m2

2 units 20 m2 25 units

3 units JO units

2 units 3 units 4 units 3 units 8 units 1 unit 1 unit l unit 1 unit 4 unlts

15 kg.

1 piece

1 piece

;;A-;¡:¡::¡¡;e;.LS

UST OF MATERIALS FOR THE OLAOE-XOCHICALL Y-MEXICO TYPE DIGESTER OF 12 m3

41

The technique to be used depends on an ínfinite number of externa! and local tactors, but it is recommended that the ferrocement technique be followed (see attached descriptions for general use); although even within it, variants can be chosen according to particular requirements. Thus, it would be best to accommodate the animals above the díqester, thereby doing away with the need for a floor for them, faciliting the loading process, and definitely improving the operation from a thermal point of view, since it will be used as the bed for the animals whose body temperature is 36º centigrade.

C. Technique to be Used

An íntelligible drawing should be made of the final arrangement. This is when the construction sequence will be decided (depending on various factors, as will be seen in point C)

The outline is done with stakes, cord, or lime. By marking each part in the selected place, logically working out the operation, and correcting possible problems, a final outline is made.

Havinq decided on the size and number of digesters proceed to the outline. The ideal is to lo cate the d igesters in such a way that the out let pi pe is lower, so as to take adva ntage of gravitatíonal force unloading, without the need for making a ramp. Otherwise, another excavation can be made, permitting entry as far as the valves with buckets, drums, pipes, etc. In the last instance, a purnp can be constructed to transfer effluentes and later remove them. The pump can be manual or mechanical (aeolic, electric or motorized.)

This is when it will be decided íf one or more tanks will be built, according to be availab.lity of land, etc. For example, íf the tank that would provide the required volurne were too large, given the land avai!able, (for example having chosen a site with a length width ratio of 6 to 1), two shorter tanks would be built a!though they would be wider and cost a little more; this would, at the same time, simplify maintenance. ln other words, there are both pros and cons.

B. Calculation, Choice of Size (s), and Outline. Once the quantity and quality of organic materíals to be processed are known, the volume of the digester is calculated.

-W:1ere there is a stable or farm -Where there will be a stable or farm -Where biodegradable products are available (human, garbage, agroindustry, water

lilies, pasture, fushery, etc.) -Where there is a good slope (topography) -Adequate terrain (soil consistency, subterranean water leve!) +Others

There are different factors that affect choice of site. They are listed as follows:

A. Site Selection

f. Preparatíon of floor-covering g. Completion and istallation of loading and unloading devices; h. Accessories.

.s. 25 5 .90

.10

o =~== :~1 o (

.eo .08 .os

__¡,__ • • al' • ~ , .20" .so 11(•20"

.1

BRON REINFORCEMENT OF BASE ( PlANT) SCALE. 1: 40

6. 00

--. -.11'..i.~----t-------~.r----------.r-----.Je- ---~"!"-- -------+··~--+-t---------------+ .ee .ee .ee .e s .e s .se .66 AG .66 .15 .e o

oopoo ty:Cin•id•l t1po: 6 111211 XOCfflCAW·MEXJCO t

COVERS (PlANT)

10018:

INDIC:ATED

pre)e1tt: flMROCt:Ml\AT COIHTlllUCTION OETAIL

P LA T E. contorne: PLAflT8

ola de SCALE. 1: 40

l l fi fi ~ .. ~·

11~01] ~ ---(> =

= ,~ 1

+--:~+ '' lf tt H tJ 1:1 1 u 1 ..

.OS HANGER PER SIDE

l2 .lll:

50

.05

.05 1

.50 .J._

.12 .¡,...-12

INTERIOR fl),, .20 1) 1/4" IRON .SO 14.I@ STAIRS

.12

.ee

.50

.12

l. 07& .875

OGpGolty: type: 1 e M 5 XOCHICALLI • ME 2 LATlftAL ll!LE. 1 NDl<lAT E D

projoot: FUIROCEMENT CONSTRUCTION DI TAi L

P L A T E oon111ln.: • aale :_

,15 .15 .45

.50

,50

l.4

.55

.so .05 .05

ola de

7.00 ----.j"-----------------------------------------------------------1--

.TO .TO .TO , 10 .10 .70 . 70 ~-------.r-- . 70

1.85 1.66

.16

FLOOR LEVEL 6) 1/4" IRON .10 STIRRUP PER SIDIE

IRON REINFORCEMENT ( LATERAL ELEVATION) SCALE. 1: 40

f.66 _.,,,...I"---- ---------------- -··--·--·-+-

• !515 . 55 • 15 fS

.... i

oopooltJ: t11~•: 18 MI >CQCHICALLl·MEXICO

P L A T 1 oontolna: aool•:

3 El.IVATION INDICATll!D

pro)•ot: Fl!'.RROCEMENT CONSTRUCTION 1>11: YAIL

OJ olade

.so

GRAVEl. ANO MORTAR F 1 LL ER

fJ 1/4" IRON

.15

.05

. 726

.326

.30

.15

.15

• 10 HANGEFIS PER SIDE

.35

.40

.60

.1!5

.05 .0!5

.11

f.85 1.65

1/4" 11 2 1/2" BOLT l.EVEL XAGONA • EAD

R EINFORCEMENT ( FRONT ELEVATION) SCALE. 1: 2 o !RON

4 o apaolty:f iooÍdol t ypo: 6 M:S XOCHICAU.1-MEXICO

oontelna: eoele: i U~l1c0r~vr

PLATI!

proj oot: F ERROCEMENT CON~TflUCT JON DETAIL

olade

IELEVATION UNSCALED LATERAL

PERSPECTIVE

l. 05

. 85

.47 .f"

111 ~ . ~ .r t. .¡..__ ·r .10 " .238 .2 36 '( .10

.67

FRONT ELEVATION Ese . 1: 15

C O V E R S ( 1 RON REINfORCEMENT)

1" .10 ,y

-.JL--·--· 2_0_3 __ .f-~ --~· 2:..:s~:s __ -,¡. . 2_e_:i ~

~=4l5~ ===!~~~ílJ===' l11

'ype: XOCHICAUI· MEXICO

oapaolt y: 1 e M?I

p L. A T E oontaln•: &-;--.;.;__--, p IUI 8 PE G TIVE

olade __ F ,.,.ROCEMENT OCONSTRUCTION projeq ~: "'" OETAIL.

I

I PERSPECTIVE

'

FORM

aoole:

5

6 SECTION B-B'

,03

GAS INLET ANO OUTLET ,32

.05

.1'>6

I" GALVANIZED PIPE

1.63

WALL PLASTERED WITH l 1/2" ALVANIZED PIPE

.115 K.20 K .40 8LOCK 2" 9A VANIZED PIPE

MORTAR

oopoolty: t)'po: 8111! 8ASOMETER XOCKICALU·MIEXICO

oontoln•: 9ECTION

.10

1/1611 BLACK PLATE

•oole: INOICATED

projeot: l'ERROCEMENT CON8TRUCTION E>ITAIL

Pl ATE SCALE 1: 20

OI olade

1.68

LEVEL ! 0.00

1

1 ·- ·-··-··-·.-·-

'

WATER LEVEL

j-.t- • 1 L .85 ! 1 -.Jo .. ~--_:_::_.:__ ,._

1 i 1/4" REJNFORCEMENT

.10

.98

, , -+ .98

1.15

1.22 1.12

. ·,. ~--,:

.so ll • 18 STAIRS .10 HAN6ER PER SIDE, [6 1/4" IRON

, ¡, 1 1 1 1 -

t) .20 ,08 .725 ..-'-·---

t r ' . ,~ = r 1

1.95 u- ~ .81'.1 .20 ~-----º 1.5~ . 71l .~ = ~ i

'/ ~ . J .88 .7211 -.¡<------·-·--+

,80

t 11 1 .05

lt * ... l. ... ~ 1..'= .. ~ J. ~ ~ . ~ ~ --J<----,ja-----·---·--.r- -., .se .sol( ... 20"".1B .10 " .70 " .TO - .TO " .10 - .70

~ .TO - . 70 .TO " .70 .20 L 00 .. --- -·---------··--------·----·-·-~· _.,,_ • 7. 00

IRON REINFORCEMENT OF BASE ( PLANT) SCALE. 1: 40

, .... /º e- ' /

1.72• ·- ~ 1 1.525 1525 I===

~

o I==

.,._ ' .r ~ ·:~ .¡a

~.10 ~ .. ~ ". ~ 11"' ... - . wr ~

.20"'" J. ~ ~ • .729 ~ .726 .725

.. V - .so .so .28 . 725 .728 . 7215 .728 • 7 2" . 726 .7 2 '5 1.00 +-·- .. ------·----·----··------.!'--

7. 25

COVERS ( PLANT) S CALE. 1: 40 o; ola de projeot: FERROCEMENT COf<IS T!tUC TI ON

DETAil

P l ATE oontolna: aoole:

t Pl Al'ITS INOICATED

oopoolty: type: te MS XOCltlCALl.l·MEXICXJ

capoolt7:{inaioel tJp•: e Na XOCHICAL.LH>n:x1co 2

PLAT E 0011toln•: aoole: L. IJLIVATION IPIDICATIO

projoo1: f'll'lftOC!Ml.!NT CONSTRUCTION DETAIL

ola de,

1 RON REINFORCEMENT (LATERAL ELEVATION) SCALE. 1: 40

-+·-·-······ ···--··-·---·--- ·-- ··-· ·--- ·-·-·-·· ---·-··-··----·-·---··- -- ····--·· 6.00

.66 .66 .68 .66 'I .. ..... ,,. ...... __ :----f------., .... "----.r----·---.¡ ..... • ----ir

.66 .e s .es .ea .ea

GRAVEL ANO MOl'ITAR F 1 LLE R

l.5JT, .::

.o .06

.35

.10 .lO .45

.:!161 .. r 1.30

.36

ois ;os

.10

NATURAL FLOOR LEVEL .Olil HAN6H PIUt SIDE l(j 1/4" ·IROlll

oapoolty:c in•id•I typo: 6 MI XO<:MICALU·MllXICO

PLATI! oont aln•: 1u1C1le: 1. KLL'!VAT108e INDICATKD

pro)nt; ,ERROCt:fllENT CONSTAUCTION DITAI L

olade

- .. ,/11-"------~~-----------.r-~ .60 . 60

GRAVEL AND MORTAR FILLER • IHi '·of .225 .t

.Ol!I .cs .13 .os .05

.41'

. 41 .54

.~ IRON REINFORCEMENT (FRONT ElEVATION) SCALE. 1: 20

HEXAGONAL - HUI> .os HAN6Ef! PER SIOE MATU&:IAL FLOOR LEVEL 1/4" ll 2 l/2w 801.T

.10 .10 ,10 .10

.05

.81'5 .30

.es

.48

1.52 l. S7 .65 - 1/4" !RON

•o•t•: INDICATIO

P L A T 1 oontolne: ILIVATIOll

4 PIRlf'tGTIVI oapoo1t1: , ....

projeot: ,IRROCEMENT CONSTRUCTION DIETAIL

OJ olade

tfp•: XOCHICAU.1-MIXICC

PERSPECTIVE

ELEVATION SCALE. 1: 15 LATERAL

---------------------- ----------,------,------------------------ ------ - --- --- ----- ------------ - -.r- 1. 70

1 ._50

FRONT ELE VATI ON SCALE. 1 : J5

.10

... +----_.,.b~---..•,...__..,.. .. _ t .1 o .-2 s , . 2 e " .1 o ., -

.,o ......

.50 -.¡---· ------~-

COVER$ (IRON REINFORCEMENT)

• P'IRftOCIUU:NT proje11t. OITAIL

ft• olade ~ CONtTRUCTION

FORM

CT 1 V E PERSPE

COV&::R

.,,.: XOCMKUllLL 1-fdl)(IC O 6

P L AT& ..... : UfOtc,n I! D

pro}eot: ,i!UtROCIMINT OOMITAUCTION DlfAfL

p l A N T SCALE. 1: 20

IROH BAR

FEEDER PIPE A-6 DETAil

l/G" MOLE

. ..¡ MAXIMUN WATl!fij Llll'll'lliL

---

.20 1.18

E l E V A T I O N 9CAL!. 1: ao

, COMINi'il FROM Ol6UTíER

og'-

1/4" IRON BAR t\!UIDU

e "·· -.::~ ,. ·,7

,,,,~,

a. ae • ,I'- ..

e t a • DETAIL A-G_

ri< MAXIMUN WATER

l LEVEL

.., I<- .. _ - - - - - '"" t;t"'" -------. l. 20

1

t.20 -1>-

, ..

i'LOC>a L 111:'/ltL

1/2" PIP! TO THi GMOwTU 1/2" TEI )> 1 . ··. /

!OGM 'l .... f-' QAS ~IS"!'!'lmllTl41lM . ..

54

Frorn experience acquired over the first constructions of the XOCHICALLl-MEXICO type digesters, sorne defficiencies have been noted caussed by lack of adequeate experience in construction with ferrocement, this repercutes in the hermetical characteristic of the digester. Another problem noticed is that related to the system of initial loading.

3.7 COMMENTS ABOUT THE APPLICATION OF THIS TECHNOLOGY

The two products mentioned can be applied to the soil as fertilizer, as inert material, or they can be used in hydroponic cultivation. The drainage liquid can also serve as food for fish and birds. lts use with larger animals (10 o/o protein, dry base, in addition to vitarnins, minerals, homones, etc.), is currently being studied. The scum can be recycled or cornposted.

The sludge from the digester has a moisture content of 88 o/o, so it can be handled like slurry. lt has the advantage of being a finished and concentrated product; app!ied to crops, it yields more as a fu nction of cumu lative effects.

3.6 UTILIZATION OF DIGESTER PRODUCTS

The water that is collected can be recirculated to economize it.

This ought to be done in such a way that the leve! does not fall below 50 cm. from the bottom, so as not to stop the process. The unloading can be done daily, enery two weeks, montly, etc. Two-thirds of the daily load can be unloaded as liquid, anda quarter as sludge.

Unloading the Digester

lt is necessary to ensure that there is no leakage, particularly through the screws of the scurn removal outlet.

The digester should be !oaded until the liquid covers the mouth of the in!et pipe. The skimrning process takes place 2 or 3 times a year , keeping in rnind that the first scurn forrns, 15 days after the initial loading, so that it becomes necessary to drain liquid as far as the lower lev.el of the scum removal outlet and to extract the scum with a device designed for the at purpose, by dragging.

i·~ is similar to that described for the Chinese system; in other words, its load is semi- continuous or continuous; the initial load is preferably made with pre-composted material. n.e addition of the initial liquid is preferably a mixture, with 10 o/o of the residual liquid from another d igester or from a septic tank.

3.5 OPERATION OF THE DIGESTER

For this type of dlgesters, organic waste, sewage, manure, organic industrial wastes, crop residues, etc., may be used as raw material. To the mixture of solids introduced into the diqester liquid {water and/or innoculators) must be added until there is an approxi- matsly 90 o/o dilution.

3.4 RAW MATERIAL FOR DIGESTER

55

5. The semicylindrical cealing shall stay underground once construction is finished, to secure a better preservation of internal heat inside the digestor.

4. Construction of the gasometer could be avoided by constructing the plant with a semicylincrical cealíng as indicated in the diagram.

b) With 50 o/o digested muds (approximately 15 to 20 days of previous digestion in another digester) to avoid un-expected floatation of cel1ulose vegetal material.

a) Excl usive!y with man u re and water, not usi ng vegeta 1 fybers. The latter cou Id be miced with the manure when the digester has regularized its ferrnentinq cycle and gas production, adding such in the way established in point 3.5 dillution could be made with the required volume of water and utilizing no more than 30 o/o of the liquid efluent, as recycling inoculous material.

3. The initial load of the digester should preferently be made as follows:

2. To make the flood gate in accordance to the one of the design in the appended drnwing (appended chart).

1. To construct the cealing in a semicylindrical form and forming a sale body together with the walls (see appended chart)

The main changes in the design recommended are:

In arder for this technology to comply with its objectives, changes in the design are being made with the purpose of avoding the mentioned problems. Nevertheless, it is very lmuortant to bear in mind the type of sand and quality of cement to be used, since if those are not the best, this will also create big problems.

3. During the initial load, the vegetal fybers and the digested materials and manure tend to float rapidly, impeding the expected bio-degradation.

2. Gas leaks in the f!ood gate dueto utilization of gaskets and sealers-wtrtch are not hermetical.

l. lnefficient sealing in the union of the taps and the cealing, this causses gas leaks.

Therefore, the main prob!ems observed are;

A JOI EX oont11lna: aaolo: --,--1 lllUYATION F. IMDI CATl'.D

UIPHftJ: typo: 18 111' XOCHICAL.U-MEXICO

projeot : DIÉTAU. OF MODIFICATIONS FOR CIALHtt AND 'L.001) 8ATI!

QI olade

1.00

SCALE. 1: 20

ELEVATION FRONT

l. 65

______________ V_'A_LV_E_F_O_R_M_U_O_S_D_RA_l_N_A_6E_

-4'-------,Jr-'"------,,¡f'OL---·----·-·---+- 0. !5 !5 0.5!5 0.55

VALVE FOR LIOUIOS ORAINA6E

SCUN &ATE

0.15

CLAMPS

OVERFLOWIN9 LEVEL

GAS STORAGE

GIROUND Lll:\IEL

0.35

o. 35

0.35

0.50

0.10

2.00 0.35

oopoolt7: t:fp•: G M' XOCHICALLl~Mt:XK:O 2

A PU ro< oontalH: •OGle: llllVATION F. INDICATED

projut: MTAIL º' lllODtflCATIONI '" GIALIH9 AND ,LOOD tAT&

CW olade

SCALE.1:4

fLOOD GATE ANO VALVE FOR LIQUIDS DRAINAGE

SIDE VIEW

DRILLllllG FOR SCREWS

CEMENT FILUNG

CLAMPS

DRAINAGE VALVE FOR MUOS

0.15

0.55

DRAINAGIE

SCALE. a: ao

ELEVATION fRONT

1.00

-~ 0.50 0.50

VALVE FOR LIQUIDS 0.10

CI.. AMPS

GAS STORAGE

0.35

0.35

OJO

enough units units unit unit u nits unit unit

2 4 1 1 3 1 1

units 20

6

4.0 1.0

35 15

3

bags of 45 kg. m3 m3 pieces kg. ro!ls (120 m2) Kg.

40

QUANTITY

7, Waterproofing agent 8. Cement pipes of 10" x 1 m. 9. Wood for ramp and structure

10. Galvanized tubing l " x 5 m. 11. Elbows l" 12. Tee 1" 13. Stopcock l" 14. Nípples ot l " x 3" l 5, Couplers of 1" 16, Universal union l "

2. River sand 3. Grave! 4. í ron 1/4" x 12 m. 5. Tie wire 6. Chicken wire

l. Cement

MATERIALS

UST OF MATERJALS FOR CONSTRUCTION OF A DIGESTER llE-MEXICO TYPE OF 10 m3

The following is a type example for construction of a 10 m3 digester.

Constructíon of the digester can be done by using different materials, which should be selected according to the economic capabilities for initial investment and to work within the estabtished guidelines. lf possib!e, the construction materials that can be found in the site where the digester is located should be used, and we recommend to use the conventional tedmiques of concrete or ferrocement to obtain better construct ion facilities.

4.2 CONSTRUCTION MATERIALS

lt is a family dígester of 10 m3, whích is located nearby the stable on source of raw material, as well as nearby the síte where the gas and the fertilizer wíll be utilized.

The entry for the mixture is located in the lower part of the digester and un!oadíng operation culd be done by the unloading pipe or overflowing device towards the unfoadíng sink,

Th is type of d igester is of a horizonta 1 spreaded construct ion. The body is located undergound with the purpose of giving a good thermal isolation. lt has a pri mary gas storaqe inside the digester (incorporated gasometer). lts geometry and operation form have beer. designed to secure a continuous functioning.

4.1 BASIC DESIGN

4. DIGESTER: llE-MEXICO TYPE (llE :- ELECTRICAR RESEARCH INSTITUTE - INSTITUTO INVESTIGACIONES ELECTRICAS

59

The construction plans of the digester with ferrocement techniques are as follows.

The unions of the feeding and unloading pipes must stay completely sealed with mixture.

When constructing the digester with ferrocement technique, it must be checked that the mixture has the sufficient water (a little dry mixture}, so that it will be fixed in the porosities left by two coats of chicken wire that is placed; then, the walls are polished with mixture, polishing them especially with waterproofing element in the internal part of the digester, with the purpose of impeding humidity and gas leaks.

The construction technique utilized in this digester varies according to the type of selectad materials.

4.3 COl\ISTRUCTJON TECHNIQUES

unit 1

unit units unit unit units

1 2 1 1 2

17. Reduction couplers of 1/2" x l" 18. Galvanized tubing of 1/2" x 5 m. 19. Stopcock 1/2" 20. Coupler of 1/2" 21. N'.pple of 1/2" x 3 22. Circular metal plate of 60 cm. x 1/8" thickness (access

and cleaning gate}

60

The overflowing device, besides being an unloading alternative, is also a water sea! that works as a relief valve in case the interna! pressure will overpass the maximum perrnissible pressure.

The digester is loaded every day with a mixture volume determined previously and the same volume is extracted by communicating receptacles towards the unloading sink, avoiding the utilization of pumps.

During the first load it is necessary to introduce the inoculous material, with the ourpose of accelerating de-composítion of the organic material, and therefore the gas ;:>roduction.

Loading is done in a continous or semi-continous form, through an entry chamber, feeding it the first load with pre+cornpound material preferably.

4.5 OPERATION OF THE OIGESTER

This digester utilized a technology of high dillution, and dueto this the raw material fed, has around 8 o/o of total salid materials in dillution (water and/or inoculous material). lt is fed with manure from 8 to 10 semi-stable cows or the equivalent in other animals; this could be mixed with wastes from harvests and a compound can be prepared in such a way that it will disgregate the organlc material.

4.4 RAW MATERIAL FOR DIGESTERS

PLATI! ciontoln•: •oolo:

1 PLANT trtDICATED

oopaolt)' :t.inaÍdo) t7p•:

10 ••• 111- NIXICO

projur: flftROC::EfUNT COIUITRUCTIOM DSTAIL

SCALE: 1. 75

PLANT GENERAL

7.00

'! , . 1 " 1.00 .18

l. 30

.18 ~

. e+·~ ·.l.

a

eo r.so

8

11 LOADING- :SINK UNLOADING SIN!<

e' +·-() '-- .._ i L-- ,__

-,1'- - .12.,~ - .., 11. - ; t

~ "¡,_,I

·~

~-- - ' ·---·---~-·---m~•--'• 1.20 . - ~------ -- ------- +- l. - . ... - ft . ,,. .,. . .,. T .,. .. -· -~ . - - . - - - - .. - ----- ..., _______ 2.00 A' -- --

.;; . ·,..·· . 1 ,Ir.. l ... : .. ,_., . ·¡-; iL ..,

.16 .12..,.._ {>~oif''..f, . . .. ..

N l. ~ 80 , 1 '(.,

s

.IS <¡)- .

1.1'0 +-· A

.15

octpaoity: (inslde) T ype: 10 m3. 11 E - MIEXICO

oontains: •OGI•: ClllOSS- 9ECTIOft 1NO1 CA T IE D

,,.1tJ.Det: FIERROCIUtlNT CON8Tft'UCTION O!TAIL .

SCALE. 1: 75

A-A' CROSS - SECTION

f"ElllROCEfdEftT FRAME WITH l5/4"

WiAE MESH 8 0111. THICK

ASBESTOS- C!MENT TUSE ( jf 20 cm. ) 7.00

.80 .95

.15

SLOPli. 2 %--

DETAI l

ASIHSTOS- CEMLUH

TUIH! ( ~ 20 owi. t

UNLOADING SINM

2 P LATE

DIGESTER 1.50 1.96

LAYER Of' CONCRETE

MIXTURE LEVIL t/4"

L--------------' o . :

@_ 70 Olll.

IRON @ 1/4"

WIT» 4 !'8 1/4" f'ERROCEMENT FRAME WITH 3/4" WIRE

MESH S =. THICK

CHAU.I u: • 12 om.

LOADING SINK

fJ'pt: 111-MEXICO

aapaolt1: l onout•I 10 1118. 3

pr~)eot: PlfUlOC IMl.NT CONITRUCTION OITAIL.

O ol SCALE. 1 30

e-e• CROSS - S~CTION

LAYll:R Of CONCRETE

@ 41!1 om. IRON , 1 4"

FER ROCE MENT .J':..!!.AM~!.!!_ __ 5/_~-~·--·- WIRE MESH 8 om. THICK

l. 20

1.50 IRON GI CEM!NT J.95

FERROCEMENT FAANE ~!!.~ ... ~'.!..~WIRI! MI!:~!!. .. 8 om. THICIC

IRON g¡j 1/4" @. 60 om.

aoal•: UtDICATID

oontoln1: CltOff·HC~

PLATE

type: 111 ~ MEXICO

capooity: l inoi.soJ 10 .. s. 4

p L A T e: oontolu: PlltlPleTIVI

O!TAIL

aoel•:

ISOMET.RY P,ojeot: PlftltOCRNllNT OOIHT,.UCTJON D16ESTER

3/4" ---

1

QJ Ola ·e

UNLOADING SI~~- OUTLET

SPILLWAV ·--tt;:r- .. ·~------ .. -~--~-~- GALVANIZED PIPE r"

4 fil 1/4"

CHAIN 12 ll 12 cm. WITH

TECHNICIAN ACCESS 60 cm. fli

FERROCEMENT FRAME WITH WIRE MESH 8 cm. THI CK

GAlVANIZEO Pl?E SUNK IN f'ERROCEMIENT

twe:.,: nz:mxr 'iil 'wrtrr w«m wucr::e =

5 PL AT 1 oontoina: •oote:

DllETAIL-PERSPEC. lNPICATl!:P SINK LOADING

, proj eot: Fll!;RROCIUH NT C ONSTftuC TI Off DIETAIL.

oopoolty: !insiol typ11: 10 r11a. 111!.- MEXIOO

DIGESTER OUTLE T

SCALE. 1: 10 SPILlWAY DETAil

. 45

GROUND LEVE] ..

ISOMETRY

66

The efluent could also be utilized for aquaculture or far poultry feeding.

The efluent that is separated each time the digester is loaded, is utilized directly in aqrlculture, and it is not advisable to storage it for a long time. The production efficiency is improved if the efluent is backfed periodically through the loading sink.

The gas is taken by a pipeline directly for its utilization, either far cooking purposes, ilJL•mination by lamps, or to move rnotors of interna! combustion. lt rnust be taken ínto

'consideration that if a separated gasometer is not designed, this design will not permit to obtain gas at constant pressure. Therefore, it is recommended to have a regular consumption with the purpose of avoiding big pressure fluctuations.

4.6 UTJUZATl(lrd OF THE DIGESTION PROOUCTS