Institutional Biogas Installer Manual - WISIONS
Institutional Biogas Installer ManualPrepared by
Institutional Biogas Plant Installer ManualDaniel Macharia and W.N.Musungu,February 2008IT Power Eastern Africa,Woodvale Groove, WestlandsP.O. Box 1532-00200Nairobi-KenyaTel: 254 20 4452593/4Fax: 254 20 4452597Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability2
Institutional Biogas Plant Installer ManualTable of Contents1. Introduction to Biogas Technology .51.1Introduction .51.3Types of fermentation.71.21.41.51.61.721.8Why Biogas .6The digestion process .7Sources of Feedstock .8The Role of Temperatures .10The pH-Value .10Retention Time .10Biogas plant construction .112.12.2Understanding the biogas system .11Types of Biogas Plants .122.2.1Biogas plant sizing .122.3.1Cement .132.3.3Gravel .132.3Construction Materials and equipments .132.3.22.3.42.3.532.3.6Sand.13Water .13Bricks .13Stones.14Step by Step Construction procedure.143.1Site Selection .143.3Digging and Pit Depth .153.23.43.53.63.73.83.9The Reference line .15Construction of Round-wall .16Dome Construction .17Construction of expansion chamber.18Construction of inlet chamber .19Lay-out of Pipeline .19Connecting to pints of use .20Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability3
Institutional Biogas Plant Installer Manual4Operation and maintenance .214.1Testing .214.1.1Feeding .224.1.3Precautions .224.1.24.254.3Gas production and use .22Maintenance and General Care .22Common operational problems .23Basic Drawings of Different Sizes of Fixed Biogas Plants .255.116m3 biogas plant .255.368m3 biogas plant .275.25.45.548m3 biogas plant .2691m3 biogas plant .28124m3 biogas plant .29Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability4
Institutional Biogas Plant Installer Manual1. Introduction to Biogas Technology1.1IntroductionBiogas technology is about capturing the gas that results from the anaerobic fermentation ofbiomass. The plant uses the natural processes of anaerobic digestion to produce biogas to producebiogas from animal waste or night soil. Biogas is a mixture of gas produced by methanogenicbacteria while acting upon biodegradable materials in an anaerobic condition.Biogas is a flammable gas produced by microbes when organic materials are fermented in a certainrange of temperature and moisture content. Biogas is about 20% lighter than air and has ignitiontemperature in the range of 6500 to 7500 C. It is odourless and colourless gas that burns with clearblue flame similar to that of LPG gas. Its calorific value is 20Mega Joules (MJ) per M3 and burnswith 60% efficiency in a conventional biogas stove.Naturally occurring bacteria (methanogenic bacteria) produce biogas during digestion orfermentation of organic matter in the absence of oxygen (anaerobic process). The gas producedconsists mainly of methane (CH4) and carbon dioxide (CO2). There are also traces of water vapour,hydrogen, nitrogen and hydrogen sulphide. This mixture of gases is combustible if the methanecontent is more than 50%. Biogas from animal dung contains approximately 60% methane.Table 2: Composition of BiogasComposition of BiogasGasesSymbolPercentage (%)MethaneCH450-70Carbon dioxideCO225-35HydrogenH25-10NitrogenN21-2Hydrogen sulphideH2STraceWater vapourH2O0.3The production of biogas occurs in two stages: Bacteria breakdown complex organic materials into short chain, simple organic acids.Organic materials and CO2 are either oxidized or reduced to CH4 by methanogenic microorganism.In this way methane is formed from fermentation of animal wastes or any cellulose organicmaterials. For fermentation to take place, several conditions such as absence of air, suitabletemperature, necessary nutrients, water contents and maintaining a suitable pH balance should bemet.Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability5
Institutional Biogas Plant Installer Manual1.2Why Biogasi. Manure for agriculture and aquaculture.Farmers conceive the importance of biogas units in terms of the availability of larger quantities ofbetter quality manure. A biogas plant in many situations doubles the availability of organic manure.The manure produced through biogas has a comparative advantage over ordinary manure in termsof both quality and quantity. About 70 - 75% of the original weight of cattle dung is conserved in abiogas unit while in open compost pits 50% or more is lost. Similarly, almost all the nitrogencontent in cattle dung is conserved in a biogas unit while a substantial part of this is lost duringcomposting. Biogas manure, known as ‘digested slurry’ contains a higher percentage of other plantnutrients as shown in the table below.Table 1: Comparison of plant nutrient content in digested slurry (DS) and farm yardmanure (FYM).Plant nutrientDS (%)FYM (%)Nitrogen (N)1.5 –2.00.5 – 1.0Phosphorus (P2O5)1.00.5 – 0.8Potash (K2O)1.00.5 -0.8It is a good source of micronutrients like zinc, iron, and manganese and copper which have becomelimited in many soils. Also, the complete digestion of cattle dung in biogas units kills seeds ofweeds. Organisms causing plant disease are also killed.It has been observed that the use of digested slurry as manure improves soil fertility and increasescrop yield by 10 -20%. It is recommended that the manure should be applied at the rate of 10tones per hectare in irrigated areas and 5 tones per hectare in dry land areas. The manure can beused in conjunction with normal dosages of chemical fertilizers. Such practice will help get betterreturns from fertilizers, minimize the loss of fertilizers from the soil and provide balance nutrition tocrops, while improving soil conditioning.ii. Domestic fuelPresently, agricultural residues and firewood are used as cooking fuel in rural areas. It is wastefulpractice as hardly 9 – 12% of their value is harnessed. Moreover, smoky kitchens are harmful tothe health of women and children. Also collection and storage of these materials is problematic, inparticular during the rainy season.Biogas is a clean and efficient fuel for cooking and lighting purposes. It saves the consumption ofkerosene, charcoal and wood. It avoids the need to collect firewood and twigs and thus saves thelabour of women and children who normally spend considerable time and energy to cover longdistances daily to collect fuel. It also eliminates the practice of indiscriminate felling of trees andconsequent soil erosion.It alleviates the drudgery of rural women’s lives and provides spare time for women’s activitiesthat can make a contribution to the family income.Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability6
Institutional Biogas Plant Installer ManualChildren can read under biogas illumination, during erratic supply of electricity or shortage ofkerosene.iii. Sanitation and healthBiogas units are effective means for the sanitary disposal of human excreta. In areas with drylatrines, the practice of carrying head loads of night – soil can be eliminated by attachinglatrines to a biogas unit. By putting all human and animal excreta into a biogas unit the problemof waste disposal is solved at the family level itself. During decomposition of night - soil in a biogasunit, most of the diseases – causing organisms are killed. This can serve as an effective control ofparasitic diseases, hookworm, roundworm, etc.The digested slurry remains free from foul smell and most pathogens. Mosquitoes and flies do notbreed in digested slurry. Thus biogas units improve sanitation.The incidence of eye diseases among women and children is also reduced as burning of biogasdoes not cause any smoke in the kitchen.Biogas, being a clean fuel, does not cause air pollution. It is considered a better fuel than naturalgas and liquefied petroleum gas because it does not contain sulphur. Sulphur, on burning, getsconverted into sulphur dioxide which is responsible for many lung diseases.The danger of explosion of biogas is less as it contains carbon dioxide which acts as a fireextinguisher. It is also lighter than air and thus easily dissipates in to the air making it impossible toreach ignitable concentrations.1.3Types of fermentation Continuous process Plug flow process Batch processIn the continuous process, the substrate or feed should be continuously added and at the sametime slurry will come from the other end continuously. In the batch process a specific amount ofsubstrate is fed into the biogas plant and left to be digested for a given duration of time afterwhich, more substrate is added. The system is more effective for substrate that is digested slowlyover a long period of time, such as straw and leaves. The plug flow process is a comparativelymore complicated system that entails the use of monitoring systems to balance the needs of themicrobes and that of the substrate during a flow through type of digestion system. The system ismainly for substrates with high water content.It is important to note that, for our purposes however, the continuous digestion is the most widelyapplied process.1.4The digestion processThe different groups of bacteria responsible for fermentation live in an interacting ecosystem. Eachtype of bacteria depends on others. Fermentation time is shortest when populations of differentbacteria are adequately balanced. The digestion process consists of 2 main phases: Acid formation andMethane formationPrepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability7
Institutional Biogas Plant Installer ManualIn the first phase, protein, carbohydrate and fat give rise to amino acids, alcohols and fatty acidsrespectively. Methane, carbon dioxide and ammonia are produced in the second phase.The slurry becomes thinner during the process of digestion as the carbon components are releasedin the form of gas. Biogas is slightly lighter than air and has an ignition temperature ofapproximately 7000C.The temperature of the flame is 8700C. ORGANIC ALTOSEFERMENTATIONCARBOXYL ACIDSACETIC ACIDCARBON DIOXIDEHYDROGENEBIOGASCH4 CO2SLURRYN, P, K,Figure 1: The bio-chemical process of anaerobic takes place in different steps as shown in thefigure below:1.5Sources of FeedstockBiogas can, in principle, be obtained from any organic material. The animal waste range from cattlemanure, chicken waste, municipal waste, kitchen waste, human waste are potential for being usedas a good source of feedstock.Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability8
Institutional Biogas Plant Installer ManualSome other types of feedstock such as straw, leaves and in particular water hyacinths can bedigested only in certain types of plants or using special conditioning techniques such as mulchingand pre-fermentation. Therefore reliable information or the general validity concerning gasproduction cannot be given.All feed materials consist of: Organic solids Water Inorganic solidsProperties of feed materialsAnimal /feed materialsCattle dungPig manureSheep droppingsPoultry manureHuman excrementStraws/ husksLeaves/grassWater hyacinthsApproxkg821Daily outputDung% livewtUrine52.50.080.525kg/m3Proportions in freshFeed materialC/N% livewt% 525Key: DM – Dry matter, ODM – Organic dry matter, C/N – Carbon Nitrogen ratioTable 3: Properties of different feed materialsBiogas is formed by digestion of the organic substances. Inorganic materials, minerals and metalsare unused ballast, which are not affected by the digestion process. The water makes the feedmaterial capable of flowing. This is important for a continuously operating biogas plant. It is as welleasier for the methane bacteria to come into contact with feed material, which is still fresh whenthe slurry is liquid.Slurry with solid content of 5-10% is particularly well suited to the operation of continuous biogasplants.All feed materials consist to a great extent of carbon (C) and Nitrogen (N). The carbon to nitrogenratio of 20:1 to 30:1 is particularly favourable. Mixture of nitrogen rich feed materials like chickenmanure and carbon rich feed materials like rice-husks give high gas production. Fermented slurrywith a lower C/N ratio has better fertilizing characteristics.Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability9
Institutional Biogas Plant Installer Manual1.6The Role of TemperaturesThe rate of biogas production depends on the physical properties of the substrate and thetemperature. The following types of digestion are distinguished according to the temperature in thedigester: Psychrophillic digestion 10-200C, retention time 100 days. Thermophollic digestion 50-600, retention time over 8days. (This type is not an option forsimple biogas plants). Mesophillic digestion 20-350C, retention time over 20 days.Simple biogas plants in tropical regions (i.e. Kenya) operate within a temperature range of between150C to 350C. To ensure a constant temperature, the plants are usually constructed underground.1.7The pH-Value1.8Retention TimeThe pH of the fermentation slurry indicates whether the digestion process is proceeding withoutdisturbance. A healthy digestion process shows a pH of 7.0 (slurry neither alkaline nor acid).The term ‘retention time’ indicates the period spent by the feed-material in the digester. Theretention time is calculated by dividing the digester volume with the daily fed material. The degreeof digestion increases with the retention time. The Longer the retention time, the higher is theexploitation rate of the material fed in the plant.A farmer with a small amount of animals should get a biogas plant with a long retention time. Thisincreases the investment costs on the one hand, but leads to a higher gas production from each kgof dung charged in the plant. A farmer with a lot of animals would rather get a plant with shortretention time. The dung is not fully exploited, but it might also not be necessary as he still gets alot of gas due to the large amount of feeding material. The shorter the retention time, the lowerthe investment costs. Retention time is also one factor in determining the size of the biogas plant.Except for the investment costs, long retention time has several advantages: The content of methane gas in the biogas mixture is increased, Reduces changes in temperature The C/N ratio becomes narrower so that the fertilization effects of the output slurry arehigher. The big volume of the digester buffers the formation of swimming and sinking layersReduces changes in pH and more energy output.A long retention time can compensate a low digester temperature. The digestion will be slower, butprolonged.Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability 10
Institutional Biogas Plant Installer Manual22.1Biogas plant constructionUnderstanding the biogas systemTop lidMixingchamberGas outletOverflowGas storageExpansionchamberDigesterFigure 2: Biogas plant layoutA biogas plant consists of three main components, namely: mixing chamber, digester andexpansion chamber. The required quantity of dung and water is mixed in the mixing chamber andthis mix in the form of slurry is allowed to flow and be digested inside the digester. The gasproduced in the digester is collected in the dome, called gasholder. The digested slurry flows to theexpansion tank from the digester through the manhole. The slurry then flows through an overflowopening to the storage pit where it is collected and taken to the fields for application as fertilizer.The gas is supplied to the point of use through a pipeline.Before deciding on the size of plant, it is necessary to collect dung for several days to determinethe average daily dung production. The amount of dung available daily helps in determining thesize of the plant. For example, if 1000 Kg of waste and 1m3 waste water is collected daily, a 150M3 biogas plant has to be selected.The impo
Institutional Biogas Plant Installer Manual Prepared by IT Power Eastern Africa. The Project is Funded by WISIONS of Sustainability 6 1.2 Why Biogas i. Manure for agriculture and aquaculture.
Nepal Biogas Plant -- Construction Manual Construction Manual for GGC 2047 Model Biogas Plant Biogas Support Programme (BSP) P.O. Box No.: 1966, Kathmandu, Nepal September, 1994 Sundar Bajgain Programme Manager Biogas Support Programme Tel. 5521742, 5534035 Email snvbsp@wlink.com.np Introduction The success or failure of any biogas plant mainly .
the biogas plant begin to produce biogas normally you should add raw fermentation materials into the biogas plant regularly. 2) For the 1.2m3 biogas plant to keep a 0.6m3/d biogas production, 20kg cow dung or 15kg pig dung is needed daily. 3) In the period of normal operation you can increase the concentration of the
biogas produced is used as energy in cooking food and heating water. The entire biogas system works normally and operates properly. But, after one year, the only problem we met is that the biogas production is low. The purpose of our study is to check if the weakness of the biogas volume is due to the dimensions of the biogas system.
biogas technology and the construction of biogas plants was launched in Cameroon. . hands-on manual. The tables and engineering drawings contained herein provide standard values . 10 m³ biogas plant produces 1.5-2 m³ and 1001 digested-slurry fertilizer per day on dung from 3-5 head of cattle or 8 - 12 pigs. With that much biogas, a 6 - 8 .
In some countries, biogas contributes significantly to the national energy balance. It may be used both as a fuel and to generate electricity. To produce these statistics, biogas data collection should focus on plant capacity and production of biogas and electricity. Project and policy monitoring More detailed biogas statistics may be required to
Biomass Biogas Biomass Biogas Biomass Technology Upgrades Maximum Potential Current. Emissions, metric tonnes (10. 3 . Mg for CO2eq) Feedstocks Collection and Transport Conversion Savings-80 -40 0 40 80 120 160. NOX PM CO2eq NOX PM CO2eq NOX PM CO2eq NOX PM CO2eq NOX PM CO2eq NOX PM CO2eq. Biogas Biomass Biogas Biomass Biogas Biomass Technology .
biogas technology specifically, the government has organized the National Project on Biogas Development nation-wide, and several NGO's have been active in implementing the program on the ground. Currently, there are thought to be about 2.5 million (Dutta et al., 2007) household and community biogas plants installed around India. 1.2 Why biogas?
time test takers of the American Board of Radiology radiation biology (left), physics (center), and clinical (right) qualifying examinations from 2005-2016 [2017 unavailable]. Reported average pass rates from 2018 are plotted as outliers (for radiation biology and physics) and labeled. Two-sided P-values (with distribution of normality confirmed by the Shapiro test) demonstrate that the .
