biogas from waste - clarke energy | fuel efficient · pdf file · 2014-12-05engines...
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Biogas from Waste
Biogas from Waste
Disposal and treatment of biologicalwaste represent a major challengefor the waste industry. For a widerange of organic substances fromagriculture, foodstuff of feedindustries, anaerobic digestion is asuperior alternative to composting.Biogas – a mixture of both methaneand carbon dioxide – is createdduring anaerobic digestion andserves as a high-energy renewablefuel that can be used as a substitutefor fossil fuels. Biogas-fuelled gasengines improve wastemanagement while maximising theuse of an economical energy supply.
Biogas Creation
Biogas results from anaerobicfermentation of organic materials.As a metabolic product of theparticipating methanogens andacidogenic bacteria, theprerequisites for its production are alack of oxygen, a pH value from 6.5to 7.5 and a constant temperature of35-45°C (mesophilic) or 45-55°C(thermophilic). The digestion periodor retention period is typicallybetween 10 and 30 days dependingupon the type of digestion employed.The anaerobic digestion systems oftoday operate largely within themesophilic temperature range.
Benefits of Waste Biogas Plants
— Production of renewable power— Treatment of a waste material— Reduced carbon emissions— Economical embedded power
production and reducedtransmission losses
— Production of soil improver— Cost effective proven technology
Waste Feedstocks
A variety of biodegradable wastefeedstocks can be used in digestionfacilities. At the outset the developershould consider what contaminantsmight be in this waste and howcould it affect the digestion processor the operation of the gas engines.
Waste-based facilities range fromsimple systems for the digestion ofcontaminant free by products, suchas those in the food preparationindustry, up to mixed wastedigestion facilities such asmechanical biological treatment(MBT) facilities accepting householdwaste. MBT facilities includecomprehensive pretreatment plantsor materials recovery facilties(MRFs) to refine the waste materialsprior to digestion.
Raw fertiliser for agricultural use
Digester
Biogas
Gasometer
Exhaust gas
Heatexchanger
Heatconsumer
Electrical energy
Gas flare
Biomass
Hygenisation
Primary pit
Biogas from Waste Schematic
Biogasfrom WasteClarke Energy is the authorised distributor and servicepartner for GE Energy’s gas engine division in a growingnumber of countries across the world. In addition toproviding high-efficiency, reliable gas engines we combinethiswith the expertise and resources to deliver unbeatableproduct support.
Whether your requirement is for the supply of a single gasengine generator or a complete turnkey power generationfacility, we can meet that need. Our ability to add value byoffering an end-to-end service, from initial proposal toreliable long-term maintenance, has led to us becoming amulti-national company with operations in ten countriesacross the globe. Our company prides itself on integrity,delivering only the highest quality products whilst providinga reliable accountable localised service.
Benefits of working with Clarke EnergyClarke Energy provides flexible solutions for your gasgeneration projects. Our services range from the supply ofa gas engine generator, through to the complete turnkeyinstallationofagaspoweredgeneration facility.ClarkeEnergyhas a dedicated, top-quality team of sales, engineering,projectmanagement, commissioningandmaintenancestaffto meet your needs. We also offer long-term maintenancecontracts backed up by a strong balance sheet, givingpeace of mind with respect to the long-term performanceof your GE gas generation equipment.
Conversion Steps from Waste to Power
The process of biogas generation isdivided into four steps:
1. Preparation of the input wastematerial – including removal ofphysical contaminants, particlesize reduction & pasteurisation
2. Digestion (fermentation),consisting of hydrolysis,acetogenesis, acidogenesis andmethanogenesis
3. Conversion of the biogas torenewable electricity and usefulheat
4. Post-treatment of the digestate
Initially the feedstock to thedigesters is received in a primary pitor liquid storage tank. From here it isloaded into the digester by variousdifferent means depending upon theconstitution of waste materials.
In the digestion tanks a series ofbiological processes are harnessedin order to produce biogas.Hydrolysis is the process where theorganic material is solubilised intothe digestion liquid. It thenundergoes the intermediate steps ofacidogenesis and acetogenesiswhich create the precursormolecules for methanogenesis.Methanogens feed off theseprecursors and produce methane asa cellular waste product.
The biogas containing thisbiologically-derived methane iscontained and captured in a gasstorage tank which is locatedseparately to the main digester, oralternatively can form its roof. Thegas storage tank acts as a buffer inorder to balance fluctuations in theproduction of gas in the digesters.
Gas Quality Considerations
The biogas may contain high levelsof water (humidity) and sulphur,depending upon the feedstock ofthe digester. Developers of biogasplants should consider the potentialfor gas contamination whendesigning their facility.
Please contact your local ClarkeEnergy sales office to provide youwith GE Energy’s technicalinstruction for fuel gas quality tounderstand the required specificlimits.
Clarke Energy is able to supply fuelgas treatment equipment either freeissue, or as part of a turnkey scopeof supply. These typically includecarbon filters, gas dehumidifiers andgas boosters.
GE Jenbacher and Biogas
The broad range of GE Jenbacherbiogas engines is specificallydesigned to run at full load with highefficiency and high availability,despite a low heating value andfluctuating gas quality and pressure.The high quality and speciallydesigned engine parts resist theimpurities that usually appear inbiogas and similar types of fuel.
Before the biogas can be fed intothe gas engines, it needs to be driedand compressed. Severecontaminants such as sulphurshould be removed if exceeding acertain level. Not only will thesemeasures considerably increase theavailability of the generator, but theywill also reduce the costs associatedwith operation.
Please request a fuel gas qualityspecification to understandoperational limits for gascontaminants in the generator’s fuel.
Waste based biogas systemstypically gain revenue in the form ofgate fees and from the sale ofrenewable electricity and heat. Thismeans that the gas engine is ofparticular importance for thesuccess of the plant. Waste facilitiesare typically required to operate atspecific times of day and have limitson the levels of waste that ispermissible to be stored on site.These factors make it essential forthe operator to have an engine withthe maximum levels of availability(running time per year) and thehighest levels of electrical efficiency,in order to convert the gas to themaximum level of electrical outputand to ensure consistent plantoperation.
Our Competence
Clarke Energy has extensiveexperience in the engineering,installation and maintenance ofgeneration facilities operating ongas derived from biological sources.
The GE Jenbacher gas engine isknown for having the highest levelsof electrical efficiency on the market.When coupled with a contractualmaintenance agreement with ClarkeEnergy, it will give peace of mind tothe customer that they will achievethe highest levels availability andhence consistent returns from theirbiogas plant.
PDM Group (Refood) Doncaster, 2 x JGMC420 + waste heat boiler
Biogengreenfinch, Westwood, UK, 2 x JGMC320
If you would like to find outmore about how ClarkeEnergy can help youdevelop your waste sectorbiogas project, pleasecontact your local office formore details.
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