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| | = <span style="font-size: 19px; line-height: 23.799999237060547px;">Industrial Digester Types</span> = | | = <span style="font-size: 19px; line-height: 23.799999237060547px;">Industrial Digester Types</span> = |
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| | == <span style="font-size: 19px; line-height: 23.799999237060547px;">Batch plants</span> == | | == <span style="font-size: 19px; line-height: 23.799999237060547px;">Batch plants</span> == |
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| | = Small-scale Digester Types = | | = Small-scale Digester Types = |
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| − | == Fixed-dome Plants<br/> ==
| + | *[[Fixed-dome_Biogas_Plants#Fixed-dome_Plants|Fixed dome Biogas Plants]]<br/> |
| − | | + | *[[Fixed-dome_Biogas_Plants#Floating-drum_Plants|Floating Drum Plants]] |
| − | A fixed-dome plant consists of a digester with a fixed, non-movable gas holder, which sits on top of the digester. When gas production starts, the slurry is displaced into the compensation tank. Gas pressure increases with the volume of gas stored and the height difference between the slurry level in the digester and the slurry level in the compensation tank.
| + | *[[Fixed-dome_Biogas_Plants#Low-Cost_Polyethylen_Tube_Digester|Low-Cost Polyethylen Tube Digester]]<br/> |
| − | | + | *[[Fixed-dome_Biogas_Plants#Balloon_Plants|Balloon Plants]] |
| − | The costs of a fixed-dome <span data-scaytid="37" data-scayt_word="biogas">biogas</span> plant are relatively low. It is simple as no moving parts exist. There are also no rusting steel parts and hence a long life of the plant (20 years or more) can be expected. The plant is constructed underground, protecting it from physical damage and saving space. While the underground digester is protected from low temperatures at night and during cold seasons, sunshine and warm seasons take longer to heat up the digester. No day/night fluctuations of temperature in the digester positively influence the bacteriological processes.
| + | *[[Fixed-dome_Biogas_Plants#Horizontal_Plants|Horizontal Plants]]<br/> |
| − | | + | *[[Fixed-dome_Biogas_Plants#Earth-pit_Plants|Earth-pit Plants]]<br/> |
| − | The construction of fixed dome plants is labor-intensive, thus creating local employment. Fixed-dome plants are not easy to build. They should only be built where construction can be supervised by experienced <span data-scaytid="40" data-scayt_word="biogas">biogas</span> technicians. Otherwise plants may not be gas-tight (porosity and cracks).
| + | *[[Fixed-dome_Biogas_Plants#Ferrocement_Plants|Ferrocement Plants]]<br/> |
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| − | The basic elements of a fixed dome plant (here the '''<span data-scaytid="44" data-scayt_word="Nicarao">Nicarao</span> Design''') are shown in the figure below.
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| − | | [[File:Nicarao biogas.gif|555px|RTENOTITLE]] <small class="IMGLEGEND">Fixed dome plant <span data-scaytid="45" data-scayt_word="Nicarao">Nicarao</span> design<ref name="TBW">TBW</ref>''': 1. Mixing tank with inlet pipe and sand trap. 2. Digester. 3. Compensation and removal tank. 4. Gasholder. 5. <span data-scaytid="47" data-scayt_word="Gaspipe">Gaspipe</span>. 6. Entry hatch, with <span data-scaytid="48" data-scayt_word="gastight">gastight</span> seal. 7. Accumulation of thick sludge. 8. Outlet pipe. 9. Reference level. 10. Supernatant scum, broken up by varying level.'''</small><br/> | |
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| − | | [[File:Fixdomscheme.gif|366px|RTENOTITLE]] <small class="IMGLEGEND">picture<ref name="OEKOTOP">OEKOTOP</ref>:Basic function of a fixed-dome <span data-scaytid="49" data-scayt_word="biogas">biogas</span> plant, 1 Mixing pit, 2 Digester, 3 Gasholder, 4 Displacement pit, 5 Gas pipe</small><br/>
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| − | === <span style="font-size: 17px;">Function</span> ===
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| − | A fixed-dome plant comprises of a closed, dome-shaped digester with an immovable, rigid gas-holder and a displacement pit, also named 'compensation tank'. The gas is stored in the upper part of the digester. When gas production commences, the slurry is displaced into the compensating tank. Gas pressure increases with the volume of gas stored, i.e. with the height difference between the two slurry levels. If there is little gas in the gas-holder, the gas pressure is low.
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| − | === Digester ===
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| − | <small class="IMGLEGEND">'''[[File:Biogastunesia01.jpg|200px|RTENOTITLE]]'''</small>
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| − | <small class="IMGLEGEND">Fixed-dome plant in <span data-scaytid="102" data-scayt_word="Tunesia">Tunesia</span>. The final layers of the masonry structure are being fixed.</small><ref name="gtz/GATE">gtz/GATE</ref>
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| − | The digesters of fixed-dome plants are usually masonry structures, structures of cement and <span data-scaytid="52" data-scayt_word="ferro-cement">ferro-cement</span> exist. Main parameters for the choice of material are:
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| − | *Technical suitability (stability, gas- and liquid tightness);
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| − | *cost-effectiveness;
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| − | *availability in the region and transport costs;
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| − | *availability of local skills for working with the particular building material. | |
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| − | <br/>Fixed dome plants produce just as much gas as floating-drum plants, ''if they are gas-tight''. However, utilization of the gas is less effective as the gas pressure fluctuates substantially. Burners and other simple appliances cannot be set in an optimal way. If the gas is required at constant pressure (e.g., for engines), a gas pressure regulator or a floating gas-holder is necessary.
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| − | === Gas-Holder ===
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| − | The top part of a fixed-dome plant (the gas space) must be gas-tight. Concrete, masonry and cement rendering are not gas-tight. The gas space must therefore be painted with a [[Plasters and coats for digesters and gas-holder|gas-tight layer]] (e.g. 'Water-proofer', Latex or synthetic paints). A possibility to reduce the risk of cracking of the gas-holder consists in the construction of a [[Optional Parts of a biogas plant#Weak ring|weak-ring]] in the masonry of the digester. This "ring" is a flexible joint between the lower (water-proof) and the upper (gas-proof) part of the hemispherical structure. It prevents cracks that develop due to the hydrostatic pressure in the lower parts to move into the upper parts of the gas-holder.
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| − | === Types of Fixed-dome Plants<br/> ===
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| − | *'''Chinese fixed-dome plant''' is the archetype of all fixed dome plants. Several million have been constructed in [[Biogas Technology in China|China]]. The digester consists of a cylinder with round bottom and top. | |
| − | *'''<span data-scaytid="103" data-scayt_word="Janata">Janata</span> model '''was the first fixed-dome design in [[Biogas Technology in India|India]], as a response to the Chinese fixed dome plant. It is not constructed anymore. The mode of construction lead to cracks in the gasholder - very few of these plant had been gas-tight. | |
| − | *'''<span data-scaytid="104" data-scayt_word="Deenbandhu">Deenbandhu</span>,''' the successor of the <span data-scaytid="105" data-scayt_word="Janata">Janata</span> plant in India, with improved design, was more crack-proof and consumed less building material than the <span data-scaytid="106" data-scayt_word="Janata">Janata</span> plant. with a hemisphere digester
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| − | *'''<span data-scaytid="109" data-scayt_word="CAMARTEC">CAMARTEC</span> model''' has a simplified structure of a hemispherical dome shell based on a rigid foundation ring only and a calculated joint of fraction, the so-called weak / strong ring. It was developed in the late <span data-scaytid="110" data-scayt_word="80s">80s</span> in [[Biogas Technology in Tanzania|Tanzania]].
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| − | | [[File:Camartecfixdome.gif|550px|RTENOTITLE]]<small class="IMGLEGEND">'''Fixed dome plant <span data-scaytid="111" data-scayt_word="CAMARTEC">CAMARTEC</span> design'''</small><ref name="TBW">TBW</ref><br/>
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| − | === Climate and Size<br/> ===
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| − | Fixed-dome plants must be covered with earth up to the top of the gas-filled space to counteract the internal pressure (up to 0,15 bar). The earth cover insulation and the option for internal heating makes them suitable for colder climates. Due to economic parameters, the recommended minimum size of a fixed-dome plant is 5 <span data-scaytid="112" data-scayt_word="m3">m<sup>3</sup></span>. Digester volumes up to 200 <span data-scaytid="221" data-scayt_word="m3">m<sup>3</sup></span> are known and possible.
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| − | === Summary ===
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| − | '''Advantages:''' Low initial costs and long useful life-span; no moving or rusting parts involved; basic design is compact, saves space and is well insulated; construction creates local employment.
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| − | Advantages are the relatively low construction costs, the absence of moving parts and rusting steel parts. If well constructed, fixed dome plants have a long life span. The underground construction saves space and protects the digester from temperature changes. The construction provides opportunities for skilled local employment.
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| − | '''Disadvantages:''' Masonry gas-holders require special <span data-scaytid="120" data-scayt_word="sealants">sealants</span> and high technical skills for gas-tight construction; gas leaks occur quite frequently; fluctuating gas pressure complicates gas utilization; amount of gas produced is not immediately visible, plant operation not readily understandable; fixed dome plants need exact planning of levels; excavation can be difficult and expensive in bedrock.
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| − | Disadvantages are mainly the frequent problems with the gas-tightness of the brickwork gas holder (a small crack in the upper brickwork can cause heavy losses of <span data-scaytid="117" data-scayt_word="biogas">biogas</span>). Fixed-dome plants are, therefore, recommended only where construction can be supervised by experienced <span data-scaytid="118" data-scayt_word="biogas">biogas</span> technicians. The gas pressure fluctuates substantially depending on the volume of the stored g''as. Even though the underground construction buffers temperature extremes, digester temperatures are generally low.''
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| − | ''Fixed dome plants can be recommended only where construction can be supervised by experienced <span data-scaytid="119" data-scayt_word="biogas">biogas</span> technicians.''<br/>
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| − | '''''Variations:''' Some companies are now looking into small <span data-scaytid="124" data-scayt_word="pre-fab">pre-fab</span> fixed dome plants made of <span data-scaytid="125" data-scayt_word="fibreglass">fibreglass</span> which appears to be a low cost alternative'' to construction intensive <span data-scaytid="126" data-scayt_word="masoned">masoned</span> plants. A custom made plant can be produced in 2 days and -after transport- installed in less than 1 day!
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| − | == Floating-drum Plants<br/> ==
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| − | Floating-drum plants consist of an underground digester and a moving gas-holder. The gas-holder floats either directly on the fermentation slurry or in a water jacket of its own. The gas is collected in the gas drum, which rises or moves down, according to the amount of gas stored. The gas drum is prevented from tilting by a guiding frame. If the drum floats in a water jacket, it cannot get stuck, even in substrate with high solid content.
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| − | [[File:Floating drum mauretania.jpg|333px|RTENOTITLE]]
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| − | <small class="IMGLEGEND">'''Floating-drum plant in <span data-scaytid="127" data-scayt_word="Mauretania">Mauretania</span>'''</small>'''<ref name="gtz/GATE">gtz/GATE</ref>'''
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| − | === The Drum<br/> ===
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| − | In the past, floating-drum plants were mainly built in India. A floating-drum plant consists of a cylindrical or dome-shaped digester and a moving, floating gas-holder, or drum. The gas-holder floats either directly in the fermenting slurry or in a separate water jacket. The drum in which the <span data-scaytid="128" data-scayt_word="biogas">biogas</span> collects has an internal and/or external guide frame that provides stability and keeps the drum upright. If <span data-scaytid="129" data-scayt_word="biogas">biogas</span> is produced, the drum moves up, if gas is consumed, the gas-holder sinks back.
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| − | === Size ===
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| − | Floating-drum plants are used chiefly for digesting animal and human feces on a continuous-feed mode of operation, i.e. with daily input. They are used most frequently by small- to middle-sized farms (digester size: <span data-scaytid="132" data-scayt_word="5-15m3">5-15m<sup>3</sup></span>) or in institutions and larger agro-industrial estates (digester size: <span data-scaytid="252" data-scayt_word="20-100m3">20-100m<sup>3</sup></span>)'''''.'''''
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| − | '''Advantages'''<br/>
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| − | '''Disadvantages''': The steel drum is relatively expensive and maintenance-intensive. Removing rust and painting has to be carried out regularly. The life-time of the drum is short (up to 15 years; in tropical coastal regions about five years). If fibrous substrates are used, the gas-holder shows a tendency to get "stuck" in the resultant floating scum.
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| − | | [[File:Floatdrumschemewaterjack s.gif|300px|RTENOTITLE]]<small class="IMGLEGEND">'''Water-jacket plant with external guide frame: 1 Mixing pit, 11 Fill pipe, 2 Digester, 3 Gasholder, 31 Guide frame, 4 Slurry store, 5 Gas pipe'''</small>'''<ref name="Sasse, 1984">Sasse, 1984</ref>'''
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| − | === Water-jacket Floating-drum Plants<br/> ===
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| − | Water-jacket plants are universally applicable and easy to maintain. The drum cannot get stuck in a scum layer, even if the substrate has a high solids content. Water-jacket plants are characterized by a long useful life and a more <span data-scaytid="134" data-scayt_word="aesthetic">aesthetic</span> appearance (no dirty gas-holder). Due to their superior sealing of the substrate (hygiene!), they are recommended for use in the fermentation of night soil. The extra cost of the masonry water jacket is relatively modest.
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| − | === Material of Digester and Drum<br/> ===
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| − | The digester is usually made of brick, concrete or quarry-stone masonry with plaster. The gas drum normally consists of 2.5 mm steel sheets for the sides and 2 mm sheets for the top. It has welded-in braces which break up surface scum when the drum rotates. The drum must be protected against corrosion. Suitable coating products are oil paints, synthetic paints and bitumen paints. Correct priming is important. There must be at least two preliminary coats and one topcoat. Coatings of used oil are cheap. They must be renewed monthly. Plastic sheeting stuck to bitumen sealant has not given good results. In coastal regions, repainting is necessary at least once a year, and in dry uplands at least every other year. Gas production will be higher if the drum is painted black or red rather than blue or white, because the digester temperature is increased by solar radiation. Gas drums made of 2 cm wire-mesh-reinforced concrete or fiber-cement must receive a gas-tight internal coating. The gas drum should have a slightly sloping roof, otherwise rainwater will be trapped on it, leading to rust damage. An excessively steep-pitched roof is unnecessarily expensive and the gas in the tip cannot be used because when the drum is resting on the bottom, the gas is no longer under pressure.
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| − | Floating-drums made of glass-fiber reinforced plastic and high-density polyethylene have been used successfully, but the construction costs are higher compared to using steel. Floating-drums made of wire-mesh-reinforced concrete are liable to hairline cracking and are intrinsically porous. They require a gas-tight, elastic internal coating. PVC drums are unsuitable because they are not resistant to UV.
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| − | === Guide Frame<br/> ===
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| − | The side wall of the gas drum should be just as high as the wall above the support ledge. The floating-drum must not touch the outer walls. It must not tilt, otherwise the coating will be damaged or it will get stuck. For this reason, a floating-drum always requires a guide. This guide frame must be designed in a way that allows the gas drum to be removed for repair. The drum can only be removed if air can flow into it, either by opening the gas outlet or by emptying the water jacket.
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| − | The floating gas drum can be replaced by a balloon above the digester. This reduces construction costs but in practice problems always arise with the attachment of the balloon to the digester and with the high susceptibility to physical damage.
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| − | === Types of Floating-drum Plants<br/> ===
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| − | <u>There are different types of floating-drum plants:</u>
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| − | *'''<span data-scaytid="136" data-scayt_word="KVIC">KVIC</span> model''' with a cylindrical digester, the oldest and most widespread floating drum <span data-scaytid="135" data-scayt_word="biogas">biogas</span> plant from India.
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| − | *'''<span data-scaytid="138" data-scayt_word="Pragati">Pragati</span> model''' with a hemisphere digester
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| − | *'''<span data-scaytid="139" data-scayt_word="Ganesh">Ganesh</span> model''' made of angular steel and plastic foil
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| − | *floating-drum plant made of pre-fabricated reinforced concrete compound units
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| − | *floating-drum plant made of <span data-scaytid="140" data-scayt_word="fibre-glass">fibre-glass</span> reinforced polyester
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| − | *low cost floating-drum plants made of plastic water containers or fiberglass drums: [[ARTI Biogas Plant|ARTI Biogas plants]]
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| − | *'''<span data-scaytid="144" data-scayt_word="BORDA">BORDA</span> model: '''The <span data-scaytid="145" data-scayt_word="BORDA-plant">BORDA-plant</span> combines the static advantages of hemispherical digester with the process-stability of the floating-drum and the longer life span of a water jacket plant.
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| − | === Summary<br/> ===
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| − | '''Advantages: '''Advantages are the simple, easily understood operation - the volume of stored gas is directly visible. The gas pressure is constant, determined by the weight of the gas holder. The construction is relatively easy, construction mistakes do not lead to major problems in operation and gas yield.
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| − | '''Disadvantages: '''Disadvantages are high material costs of the steel drum, the susceptibility of steel parts to corrosion. Because of this, floating drum plants have a shorter life span than fixed-dome plants and regular maintenance costs for the painting of the drum.
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| − | == Low-Cost <span data-scaytid="146" data-scayt_word="Polyethylen">Polyethylen</span> Tube Digester<br/> ==
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| − | === Digester ===
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| − | In the case of the Low-Cost Polyethylene Tube Digester model which is applied in [[Low-Cost Polyethylene Tube Digesters in Bolivia|Bolivia]] (Peru, Ecuador, Colombia, Centro America and Mexico), the tubular polyethylene film (two coats of 300 microns) is <span data-scaytid="147" data-scayt_word="bended">bended</span> at each end around a 6 inch PVC drainpipe and is wound with rubber strap of recycled tire-tubes. With this system a hermetic isolated tank is obtained (figure <span data-scaytid="148" data-scayt_word="td1">td1</span>).
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| − | [[File:In Outlet winding Tube Digester.jpg|thumb|left|400px|Picture td2: Winding In-/Outlet Tube Digester|alt=In Outlet winding Tube Digester.jpg]]
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| − | <span style="font-size: 11px; text-align: center;">Picture <span data-scaytid="164" data-scayt_word="td2">td2</span>: Winding In-/Outlet Tube Digester.</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | <br/>[[File:Low Cost Polyethylene Tube Digester Scheme.jpg|thumb|center|500px|Low Cost Polyethylene Tube Digester Scheme.jpg|alt=Low Cost Polyethylene Tube Digester Scheme.jpg]]
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| − | <span style="font-size: 11px; text-align: center;">Figure <span data-scaytid="492" data-scayt_word="td1">td1</span>: Scheme of Low-cost Polyethylene Tube Digester. </span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | ''One of the 6" PVC drainpipes serves as inlet and the other one as the outlet of the slurry. In the tube digester finally, a hydraulic level is set up by itself, so that as much quantity of added prime matter (the mix of dung and water) as quantity of fertilizer leave by the outlet.<br/>Because the tubular polyethylene is flexible, it is necessary to construct a "cradle" which will accommodate the reaction tank, so that a trench is excavated (picture <span data-scaytid="153" data-scayt_word="td3">td3</span>).''
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| − | === Gasholder and Gas Storage Reservoir<br/> ===
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| − | The capacity of the gasholder corresponds to 1/4 of the total capacity of the reaction tube (figure <span data-scaytid="155" data-scayt_word="td1">td1</span>).
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| − | To overcome the problem of low gas flow rates, two 200 microns tubular polyethylene reservoirs are installed close to the kitchen, which gives a 1,3 m³ additional gas storage (picture <span data-scaytid="157" data-scayt_word="td4">td4</span>).
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| − | <span style="line-height: 1.5em; font-size: 11px; text-align: center;">Picture <span data-scaytid="39" data-scayt_word="td4">td4</span>: Gas Storage Reservoir</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | <span style="line-height: 1.5em; font-size: 11px; text-align: center;">Picture <span data-scaytid="60" data-scayt_word="td3">td3</span>: Tube Digester </span><span data-scaytid="59" data-scayt_word="Altiplano" style="line-height: 1.5em;"><span style="font-size: 11px; text-align: center;">Altiplan</span><span style="font-size: 11px; text-align: center;">o</span></span><span style="line-height: 1.5em; font-size: 11px; text-align: center;">of Bolivia</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | === <span data-scaytid="315" data-scayt_word="Biogas">Biogas</span> Supply Line<br/> ===
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| − | The track of <span data-scaytid="316" data-scayt_word="biogas">biogas</span> up to the kitchen is <span data-scaytid="321" data-scayt_word="realised">realised</span> directly. The digester system works with a <span data-scaytid="317" data-scayt_word="biogas">biogas</span> pressure between 15 - 20 cm water column. A security valve, which is constructed of a 1, 5 l or 2, 0 l PET refreshment bottle (picture <span data-scaytid="322" data-scayt_word="td5">td5</span>), <span data-scaytid="323" data-scayt_word="controlls">controlls</span> the pressure. For the supply line a 1/2" flexible PVC tube is used.
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| − | [[File:Tube Digester Security Valve.jpg|border|center|300px|Tube Digester Security Valve.jpg|alt=Tube Digester Security Valve.jpg]]
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| − | <p style="text-align: center;"><span style="font-size: 11px;">Picture <span data-scaytid="324" data-scayt_word="td5">td5</span>: Tube Digester Security Valve</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref></p>
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| − | ''[[File:Scheme of the biogas supply line tube digester.jpg|border|center|650px|Scheme of the biogas supply line tube digester.jpg|alt=Scheme of the biogas supply line tube digester.jpg]]''<span style="font-size: 11px;">Figure <span data-scaytid="326" data-scayt_word="td6">td6</span>: Scheme of the gas supply line.</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | === Modification ===
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| − | To be able to work in different altitudes and climate zones, in Bolivia the Low-Cost Polyethylene Tube Digester was modified into three climate types.<br/>The three implanted types are calculated for 4 - 5 hours of <span data-scaytid="327" data-scayt_word="Biogas">Biogas</span> using per day. The digesters differ in size and protection of the system.
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| − | The <span data-scaytid="331" data-scayt_word="biodigester">biodigester</span> for the Bolivian <span data-scaytid="329" data-scayt_word="Altiplano">Altiplano</span> (picture <span data-scaytid="330" data-scayt_word="td7">td7</span>) is enclosed in a greenhouse of polyethylene (250 microns), supported by two lateral adobe walls of 40 cm thickness above the hole length of the trench. This lateral walls accumulate the heat of the greenhouse effect, that with freezing temperatures during winter nights, they maintain the digester in function, by the own high thermal inertia. So it is possible to <span data-scaytid="334" data-scayt_word="realise">realise</span> the installation of a working digester in an altitude of more than 4.500 m about sea level.
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| − | For the digesters in the valley and tropical zones (picture <span data-scaytid="339" data-scayt_word="td8">td8</span>) there is no need to install a greenhouse, but it is to protect the polyethylene of the <span data-scaytid="336" data-scayt_word="biodigester">biodigester</span> about the direct solar radiation with a half shade red or better a roof. Additional it is recommended to protect this systems with a wire-mesh fence against animals like e.g. cows or chickens.
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| − | [[File:Low Cost Tube Digester Altiplano.JPG|thumb|right|450px|Low Cost Tube Digester Altiplano.JPG|alt=Low Cost Tube Digester Altiplano.JPG]]
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| − | <p style="text-align: center;"><span style="font-size: 11px;">Picture <span data-scaytid="337" data-scayt_word="td7">td7</span>: Low-cost Tube Digester <span data-scaytid="338" data-scayt_word="Altiplano">Altiplano</span> of Bolivia</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref></p>
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| − | [[File:Low Cost Tube Digester Valley.JPG|thumb|right|300px|Low Cost Tube Digester Valley.JPG|alt=Low Cost Tube Digester Valley.JPG]]
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| − | <span style="font-size: 11px; text-align: center;">Picture <span data-scaytid="340" data-scayt_word="td8">td8</span>: Low-cost Tube Digester - Valley</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | <u>'''Advantages'''</u>
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| − | Advantages are that tubular polyethylene is produced in most countries. The choice of supplementary fittings and related materials has been limited to those available locally on farms or in rural markets; they are the basic components of sanitary installations which are similar all over the world. The polyethylene tubular film <span data-scaytid="344" data-scayt_word="biodigester">biodigester</span> technology is a cheap and simple way to produce gas.
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| − | <u>'''Disadvantages'''</u>
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| − | Disadvantages are the lower gas pressure (20 cm water column / 19,6 mbar) than in the <span data-scaytid="346" data-scayt_word="fixed-dom">fixed-dom</span> system or floating drum system<span style="font-style: italic">. </span>You can't walk or use the area over the digester like in the case of the underground plants. There is a need to protect the tubular polyethylene against e.g. cows, because it could burst when the animal jumps into the digester.
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| − | [[File:Tube Digester Altiplano Carabuco Bolivia.JPG|thumb|center|400px|Tube Digester Altiplano Carabuco Bolivia.JPG|alt=Tube Digester Altiplano Carabuco Bolivia.JPG]]
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| − | <span style="font-size: 11px;">Tube Digester <span data-scaytid="347" data-scayt_word="Altiplano">Altiplano</span> - <span data-scaytid="349" data-scayt_word="Carabuco">Carabuco</span>/Bolivia</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | [[File:Tube Digester Altiplano inside.jpg|thumb|center|300px|Tube Digester Altiplano inside.jpg|alt=Tube Digester Altiplano inside.jpg]]
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| − | <span style="font-size: 11px;">Tube Digester Inside - <span data-scaytid="350" data-scayt_word="Carabuco">Carabuco</span>/Bolivia</span><ref name="GTZ / EnDev Bolivia">GTZ / EnDev Bolivia</ref>
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| − | To contrast these simple <span data-scaytid="351" data-scayt_word="biogas">biogas</span> plants, figure 2 gives an impression about dimensions of industrial plants which are, for example, built in Europe.
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| − | [[File:Indplant.gif|605px|RTENOTITLE]]
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| − | <small class="IMGLEGEND">Fig. 2: Industrial <span data-scaytid="353" data-scayt_word="biogas">biogas</span> plant with utilization of domestic organic wastes</small><ref name="TBW">TBW</ref>
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| − | === Experience with <span data-scaytid="356" data-scayt_word="Plythylene">Plythylene</span> <span data-scaytid="354" data-scayt_word="Biogas">Biogas</span> Digester (<span data-scaytid="358" data-scayt_word="PBD">PBD</span>)<br/> ===
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| − | *[[Experience with Polyethylene Biogas Digester (PBD) from some countries|Experience with Polyethylene Biogas Digester (PBD) from some countries (click HERE)]]
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| − | === Variation <span data-scaytid="363" data-scayt_word="Tyre">Tyre</span> Tube Household Digester<br/> ===
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| − | *[https://energypedia.info/TyreTube Biogas Plant Variation tyre tube household digester]
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| − | == <span style="font-size: 17px;">Balloon Plants</span> ==
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| − | A balloon plant consists of a heat-sealed plastic or rubber bag (balloon), combining digester and gas-holder. The gas is stored in the upper part of the balloon. The inlet and outlet are attached directly to the skin of the balloon. Gas pressure can be increased by placing weights on the balloon. If the gas pressure exceeds a limit that the balloon can withstand, it may damage the skin. Therefore, safety valves are required. If higher gas pressures are needed, a gas pump is required. Since the material has to be weather- and UV resistant, specially stabilized, reinforced plastic or synthetic <span data-scaytid="10" data-scayt_word="caoutchouc">caoutchouc</span> is given preference. Other materials which have been used successfully include <span data-scaytid="11" data-scayt_word="RMP">RMP</span> (red mud plastic), <span data-scaytid="12" data-scayt_word="Trevira">Trevira</span> and butyl. The useful life-span does usually not exceed 2-5 years.
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| − | '''Advantages''': Standardized prefabrication at low cost, low construction sophistication, ease of transportation, shallow installation suitable for use in areas with a high groundwater table; high digester temperatures in warm climates; uncomplicated cleaning, emptying and maintenance; difficult substrates like water hyacinths can be used.
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| − | Balloon <span data-scaytid="15" data-scayt_word="biogas">biogas</span> plants are recommended, if local repair is or can be made possible and the cost advantage is substantial.
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| − | '''Disadvantages''': Low gas pressure may require gas pumps; scum cannot be removed during operation; the plastic balloon has a relatively short useful life-span and is susceptible to mechanical damage and usually not available locally. In addition, local craftsmen are rarely in a position to repair a damaged balloon. There is only little scope for the creation of local employment and, therefore, limited self-help potential.
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| − | '''Variations:''' A variation of the balloon plant is the channel-type digester, which is usually covered with plastic sheeting and a sunshade (fig.1-E). Balloon plants can be recommended wherever the balloon skin is not likely to be damaged and where the temperature is even and high.
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| − | [[File:Foilplant.jpg|348px|RTENOTITLE]] <small class="IMGLEGEND">Photo<ref name="Henning"> Henning</ref>:Small "foil-plant" (Ivory Coast)</small>
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| − | [[File:Plant-types s.gif|500px|Plant-types s.gif|alt=Plant-types s.gif]] <small class="IMGLEGEND">Fig. 1<ref name="Biogas Plants, L. Sasse, GATE, 1988, p. 14">Biogas Plants, L. Sasse, GATE, 1988, p. 14</ref>: Simple <span data-scaytid="17" data-scayt_word="biogas">biogas</span> plants. Floating-drum plant (A), fixed-dome plant (B), fixed-dome plant with separate gas holder (C), balloon plant (D), channel-type digester with plastic sheeting and sunshade (E).</small>
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| − | === Horizontal Plants<br/> ===
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| − | Horizontal <span data-scaytid="20" data-scayt_word="biogas">biogas</span> plants are usually chosen when shallow installation is called for (groundwater, rock). They are made of masonry or concrete.
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| − | '''Advantages: '''Shallow construction despite large slurry space.
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| − | '''Disadvantages''': Problems with gas-space leakage, difficult elimination of scum.
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| − | <blockquote></blockquote>
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| − | === Earth-pit Plants<br/> ===
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| − | Masonry digesters are not necessary in stable soil (e.g. <span data-scaytid="22" data-scayt_word="laterite">laterite</span>). It is sufficient to line the pit with a thin layer of cement (wire-mesh fixed to the pit wall and plastered) in order to prevent seepage. The edge of the pit is reinforced with a ring of masonry that also serves as anchorage for the gas-holder. The gas-holder can be made of metal or plastic sheeting. If plastic sheeting is used, it must be attached to a quadratic wooden frame that extends down into the slurry and is anchored in place to counter its buoyancy. The requisite gas pressure is achieved by placing weights on the gas-holder. An overflow point in the peripheral wall serves as the slurry outlet'''.'''
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| − | '''Advantages''': Low cost of installation (as little as 20% of a floating-drum plant); high potential for self help approaches.
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| − | '''Disadvantages''': Short useful life; serviceable only in suitable, impermeable types of soil.
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| − | Earth-pit plants can only be recommended for installation in impermeable soil located above the groundwater table. Their construction is particularly inexpensive in connection with plastic sheet gas-holders.
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| − | === <span data-scaytid="23" data-scayt_word="Ferrocement">Ferrocement</span> Plants<br/> ===
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| − | The <span data-scaytid="24" data-scayt_word="ferro-cement">ferro-cement</span> type of construction can be applied either as a self-supporting shell or an earth-pit lining. The vessel is usually cylindrical. Very small plants (Volume under 6 <span data-scaytid="25" data-scayt_word="m3">m<sup>3</sup></span>) can be prefabricated. As in the case of a fixed-dome plant, the <span data-scaytid="85" data-scayt_word="ferrocement">ferrocement</span> gasholder requires special sealing measures (proven reliability with cemented-on <span data-scaytid="86" data-scayt_word="aluminium">aluminium</span> foil).
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| − | '''''Advantages''''': Low cost of construction, especially in comparison with potentially high cost of masonry for alternative plants; mass production possible; low material input.
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| − | '''Disadvantages''': Substantial consumption of essentially good-quality cement; workmanship must meet high quality standards; uses substantial amounts of expensive wire mesh; construction technique not yet adequately time-tested; special sealing measures for the gas-holder are necessary. Ferro-cement <span data-scaytid="29" data-scayt_word="biogas">biogas</span> plants are only recommended in cases where special <span data-scaytid="30" data-scayt_word="ferro-cement">ferro-cement</span> know-how is available. <!-- Navigation Footer -->
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| | = Dry Fermentation Plants<br/> = | | = Dry Fermentation Plants<br/> = |
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| | = Further Information<br/> = | | = Further Information<br/> = |
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| | [https://www.dropbox.com/sh/q0zvpvr4t1y7uxt/f5gvrXFj8c/01_Functional and operative information/02_Construction of a Biogas Plant Collection of Publications on Construction of Biogas Plants] | | [https://www.dropbox.com/sh/q0zvpvr4t1y7uxt/f5gvrXFj8c/01_Functional and operative information/02_Construction of a Biogas Plant Collection of Publications on Construction of Biogas Plants] |
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| | = References<br/> = | | = References<br/> = |
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| | + | [[Category:Biogas]] |
| | [[Category:Bioenergy]] | | [[Category:Bioenergy]] |
| − | [[Category:Biogas]]
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Control glasses for an industrial digester for solid organic waste, Germany[1]
