Measuring Small-scale Biogas Capacity And Production
Measuring small-scale biogascapacity and production
Copyright IRENA 2016Unless otherwise stated, this publication and material featured herein are the property of the International RenewableEnergy Agency (IRENA) and are subject to copyright by IRENA.Material in this publication may be freely used, shared, copied, reproduced, printed and/or stored, provided that all suchmaterial is clearly attributed to IRENA and bears a notation that it is subject to copyright ( IRENA), with the year ofthe copyright.Material contained in this publication attributed to third parties may be subject to third party copyright and separateterms of use and restrictions, including restrictions in relation to any commercial use.ISBN 978-92-95111-12-7 (PDF)This report should be cited: IRENA (2016), Measuring small-scale biogas capacity and production, InternationalRenewable Energy Agency (IRENA), Abu DhabiAbout IRENAThe International Renewable Energy Agency (IRENA) is an intergovernmental organisation that supports countries intheir transition to a sustainable energy future, and serves as the principal platform for international co-operation, acentre of excellence, and a repository of policy, technology, resource and financial knowledge on renewable energy.IRENA promotes the widespread adoption and sustainable use of all forms of renewable energy, including bioenergy,geothermal, hydropower, ocean, solar and wind energy, in the pursuit of sustainable development, energy access,energy security and low-carbon economic growth and prosperity. www.irena.orgPrepared by Samah Elsayed, IRENA Programme Officer, Capacity Building in StatisticsFor further information or to provide feedback, please contact the IRENA statistics team (statistics@irena.org).This report is available for download: www.irena.org/publications.DisclaimerThis publication and the material featured herein are provided “as is”, for informational purposes.All reasonable precautions have been taken by IRENA to verify the reliability of the material featured in this publication.Neither IRENA nor any of its officials, agents, data or other third-party content providers or licensors provides anywarranty, including as to the accuracy, completeness, or fitness for a particular purpose or use of such material, orregarding the non-infringement of third-party rights, and they accept no responsibility or liability with regard to the useof this publication and the material featured therein.The information contained herein does not necessarily represent the views of the Members of IRENA, nor is it anendorsement of any project, product or service provider. The designations employed and the presentation of materialherein do not imply the expression of any opinion on the part of IRENA concerning the legal status of any region,country, territory, city or area or of its authorities, or concerning the delimitation of frontiers or boundaries.
CONTENTS1.INTRODUCTION . 1What is a biogas digester? . 1Why are biogas statistics collected? . 1Guidance structure . 22.THE MAIN PARAMETERS AFFECTING BIOGAS PRODUCTION . 3Digester technologies . 3Plant capacity . 4Total feedstock volume . 4Feedstock properties . 5Feedstock retention time. 5Temperature . 53.PLANT CAPACITY . 6Administrative data . 6Survey of standardised biogas plant types . 7Survey of biogas plant dimensions . 74.BIOGAS PRODUCTION AND CONSUMPTION . 12Plant capacity . 13Appliance use . 13Feedstock use . 15Fuel substitution . 18Direct measurement .195.OTHER INFORMATION ABOUT BIOGAS PRODUCTION . 20Financial and technical performance . 20Emissions reductions. 21Energy access and socioeconomic impacts . 21REFERENCES . 23APPENDIX 1: BIOGAS PLANT CALCULATION TABLES . 25APPENDIX 2: BIOGAS DATA COLLECTION IN CHINA . 29Rural renewable energy statistics system . 29Green county monitoring system . 30
1. INTRODUCTIONInterest in small-scale biogas technologies hasincreased in recent years across Africa, Asia andLatin America. This has been driven by the socioeconomic and environmental benefits of usingbiogas, such as reduced firewood and keroseneconsumption, lower emissions of greenhouse gasesand indoor air pollutants and the possibilities to usebiogas to treat human and animal wastes (Bunny &Besselink, 2006). Given this trend, biogas use needsto be accurately monitored and measured.This guide aims to help energy statisticians tomeasure and estimate the capacity and productionof biogas plants, as well as other aspects of biogasproduction. The main focus is on data collectionfrom small-scale household, communal or farmbiogas plants that produce biogas in a continuousprocess (i.e. feedstocks are added and biogasremoved every day).The methods described here may also be used forlarge-scale biogas plants or plants producingelectricity, but such facilities should have monitoringdevices to measure production more easily andaccurately.WHAT IS A BIOGAS DIGESTER?The main part of a biogas plant is the digester, whichis an airtight container in which bacteria break downorganic waste through a process of anaerobicfermentation.1 This generates a gas (biogas) that ismostly methane and carbon dioxide (CO2). This gascan be used for cooking, heating and lighting, or itcan be used to generate electricity. As more materialis added to the digester, a liquid waste (slurry) isalso produced, which can be used as a fertiliser.Biogas digesters can vary greatly in capacity,ranging from small-scale units used by householdsto larger communal and industrial digesters.Feedstocks added to the digester can include manytypes of biomass such as animal, food andagricultural waste, but materials that are difficult forthe bacteria to digest (e.g. wood) should beavoided. The amount of biogas produced dependson a range of factors including the type and amountof biomass used, the digester size and temperature.WHY ARE BIOGAS STATISTICS COLLECTED?The amount and type of biogas data collected willdepend on how this information will be used. Forexample, project and policy monitoring may requirethe collection of specific and detailed data, while1KEY REQUIREMENTS FOR DIGESTER OPERATION An airtight environment with no oxygenModerate temperaturesNo lightSmall feedstock particles withbroken down fibres and minimallignin (wood) contentFor some feedstocks a starterbacteria is also necessarymonitoring of renewable energy targets may onlyneed very basic data that can be obtained from afew biogas questions in a census or householdsurvey. The following are some examples of howbiogas statistics may be used and the sorts of datathat might be needed.National energy statisticsIn some countries, biogas contributes significantlyto the national energy balance. It may be used bothas a fuel and to generate electricity. To producethese statistics, biogas data collection should focuson plant capacity and production of biogas andelectricity.Project and policy monitoringMore detailed biogas statistics may be required tomonitor implementation of biogas projects,programmes and policies. Important variables tomonitor can include: the number and size of biogasplants installed; their condition; the amount ofbiogas produced; and a range of socio-economicimpacts.Tracking progress towards targetsHousehold biogas plants are often used to producebiogas for cooking, as biogas is a clean and modernalternative to using solid biofuels. Statistics aboutthe numbers of households using biogas are neededto track progress towards clean energy goals, suchas the energy access target under the SustainableDevelopment Goal for energy (SDG 7) “to ensureaccess to affordable, reliable, sustainable andmodern energy for all.”Measuring environmental impactsBiogas can reduce the environmental impact ofenergy use in many ways. Switching to biogas canreduce CO2 emissions from energy use, as well asmethane emissions (if biogas is produced fromAnaerobic fermentation means that the fermentation or digestion occurs in the absence of oxygen.1
waste). It can also have positive benefits for indoorair pollution and land degradation when it replacesthe use of solid biofuels. To measure these impacts,information may need to be collected about severalsocial and environmental indicators as part of thecollection of biogas statistics.International energy statisticsThis guide, produced as part of the statisticscapacity building programme at the InternationalRenewable Energy Agency (IRENA), is intended tohelp countries collect and report their biogas data inan internationally comparable format.In energy balances, biogas data is usually reportedin megajoules (MJ), so conversion factors to convertfrom cubic metres of gas to MJ are given in section4 of the guidance. Other advice is also given in thetext about where different elements of biogasproduction and consumption should be recorded inan energy balanceWith the methodologies and techniques describedhere, it is hoped that the availability of biogas datawill improve, so that IRENA’s statistics will capturemore information about this rapidly growing part ofthe renewable energy sector.2GUIDANCE STRUCTUREThe remainder of this document is divided into foursections.The first section describes the main variablesinfluencing digester operation such as the digestertechnology, the type and amount of feedstock used,plant capacity and digester temperature.The second section looks at two ways to collect dataabout the capacity of a biogas plant. This includesguidance about how to make volume calculationsbased on typical biogas plant designs.A third section describes five different ways toestimate or measure biogas production andconsumption, including: estimates based ondigester size; estimates based on appliance use;estimates based on feedstock use; estimates basedon fuel substitution; and direct measurement of gasproduction.The final section describes how the environmentaland socio-economic impacts of biogas use may bemonitored, including: emissions reductions; effectson women and children; and health benefits.
2. THE MAIN PARAMETERS AFFECTING BIOGAS PRODUCTIONThis section presents an overview of some of themain variables that affect biogas productionincluding: the digester type; digester size (measuredeither as volume or expected production level); thetype and amount of feedstock used in the digester;feedstock retention time; and temperature.KEY DIGESTER TYPES Fixed dome plant(Hemisphere, Deenbandhu andChinese designs) Floating drum plant Balloon/bag digesterDIGESTER TECHNOLOGIESThere are a number of different designs of smallscale biogas digesters and recording the type ofdigester is important for estimating its capacity,particularly in cases where the digester is partlyunderground. If the owner of the digester has anoperator’s manual or watched it being installed, thenthey should know what type of digester they have.If they do not know, then the data collector will needto look at the digester to determine its type.the dome at the top of the digester. Biogas isremoved from the digester using a pipe attached tothe top of the dome.As biogas is produced, slurry is pushed out from thedigester through the outlet pipe into a displacementtank. When the biogas is used, this slurry flows backinto the digester. Some designs may also include anadditional gas storage tank connected to the gasoutlet pipe.The typical Chinese fixed dome plant often consistsof a cylindrical digester with a round top and flat orcurved bottom. Other variations of the fixed domeplant include the Deenbandhu and Deenbandhu2000 model biogas plants developed in India, whichhave a dome at the top and a curved base(Kudaravelli, 2013). Another type is the CAMARTECmodel designed by GIZ for use in Tanzania, which isbuilt as a series of brick rings in the shape of a domeon top of a flat base (Sasse et al, 1991).Floating drum plantFixed dome plantFigure 2: Floating drum plantFigure 1: Fixed dome plantThe fixed dome plant was originally developed inChina, where there are now several million of thesetypes of biogas plant.The digester in a fixed dome plant consists of anunderground pit lined with concrete or brick, with aninlet pipe that is used to add feed to the digester.Gas is produced under pressure and is stored underThe floating drum plant was designed anddeveloped in India. It comprises a brick lined pit thatis often partly underground (the digester) and adrum above ground is used as the gas collector. Apopular design is the Khadi and Village IndustriesCommission (KVIC) digester. The drum is typicallymade of steel although some newer designs usefiberglass reinforced plastic.Water and feedstocks are combined in a mixing pitwhich then flows into the underground digesterthrough the inlet pipe. As gas is produced, it iscollected in the drum, which moves up and down acentral guide pipe depending on the amount of gasbeing stored. The gas is held under pressure from3
the weight of the drum, which can be increased withthe addition of weights.As more feedstocks are added, slurry flows outthrough the outlet pipe. A gas outlet pipe is alsoattached to the drum to remove gas from the plant.A variation of this design is the small-scale aboveground floating drum plant developed in India bythe Appropriate Rural Technology Institute (ARTI).The ARTI biogas plant is made for the digestion ofhousehold food waste and is made from two plasticwater tanks with their tops removed and the smallertank placed upside down inside the larger one. Pipesare added to the outer tank to add feedstocks andremove the slurry and a gas outlet pipe is added tothe top of the inner tank (AIDG, 2009).capacity in this way. For example, in India, theexpected amount of gas produced each day may becalled the plant capacity or plant size. Biogasproduction can be reported in this way because thefeedstocks used in India usually do not change verymuch, leading to a predictable daily productionlevel. In other countries (e.g. China), the feedstocksused for biogas production vary greatly from placeto place and at different times, so plant capacity isrecorded as the volume of the plant rather than thevolume of production per day (INFORSE South Asia,2007).To avoid confusion, this guidance will use “rateddaily gas production” in calculations when thecalculations use an expected daily production leveland will use “total plant volume” if the calculationsare referring to the volume of the plant.Balloon/bag digesterRated daily gas productionThe rated daily gas production is the volume of gasthat a biogas plant is designed to produce each dayif operated under optimal conditions. Measured inm3/day, this shows the amount of biogas that isproduced (not the amount of methane).Figure 3: Balloon digesterBalloon digesters are often used in Latin Americancountries. This type of digester is usually made froma large, strong plastic bag connected to a piece ofdrainpipe at either end, with these pipes being usedto add feedstocks and remove slurry.To avoid damage to the bag, the digester is usuallyplaced in a trench and the trench is slightly deeperat the slurry outlet so that the slurry will settle there.As gas is produced the top of the bag inflates andthe gas can be removed through an outlet pipe inthe top of the bag. Gas pressure can be increased byplacing weights on top of the bag (Vögeli et al,2014).In China, a common variation of this design is thebag digester, which is a circular concrete, brick orplastic lined container covered with a plastic bag ortent. As with a fixed dome plant, inlet and outletpipes are used to add feedstocks and remove slurryand the gas is collected and removed from the bag.PLANT CAPACITYThe capacity of a biogas plant is the maximum totalvolume of gas and slurry that it can contain.However, not all countries measure biogas plant4The energy content of biogas will mostly depend onthe methane content of the biogas, which should beabout 65%. This needs to be taken into accountwhen converting figures from gas production toenergy production. Biogas will also contain othergases such as carbon dioxide, nitrogen and smallamounts of hydrogen, but these have little impacton the energy content of the biogas.Total plant volumeThe total plant volume is the sum of twocomponents: the digester volume and the gasstorage volume. It is measured in m3.The digester volume is the maximum amount ofslurry that the plant can hold, while the gas storagevolume is the amount of gas it can hold when full ofslurry. The latter is usually a proportion of theformer. The digester volume may also include asafety m
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
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 .
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.
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 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 .
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?
surface, biogas intake surface, HHO intake surface. S5 HHO Injector Biogas Injector S1 S2 S3 S4 -correction nozzle Fig. 1: Retrofit intake manifold of the Samdi S3600B-1 engine for biogas-HHO fuel supply In the simulation, biogas is denoted by MxCy where 10x is mole fraction of CH 4 (%) and 10y is mole fraction of CO 2 (%). HHO gas contains 1/3 .
A. Thomas Perhacs is the author, creator, and visionary behind the Mind Force Method. He is also the President of Velocity Group Publishing and Director of The
