Basics of Anaerobic Digestion

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About the basics of anaerobic digestion, application and basics of laboratory analyisis.


<ul><li><p>Introduction to anaerobic digestionBiogas STU</p><p>ERASMUS EXCHANGE STUDENTSFebruary 2014___________________________Ing. Juan Jos Chvez</p></li><li><p>Ing. Juan Jos Chvez</p><p>Part 1: Waste</p></li><li><p>Ing. Juan Jos Chvez</p><p>Anthropogenic activities</p><p> Anthropogenic activity (Anthropos means human, geny means origin): An effect or object originated by human activity</p></li><li><p>Ing. Juan Jos Chvez</p><p>Waste</p><p> Definition of waste, according to the EU Waste Framework Directive:</p><p>Any substance or object which the holder discards or intends or is required to discard</p><p> Waste management: All the processes involved in dealing with the waste of human activities, including its prevention, reduction, collection, transport, handling, storage, recycling, processing, incinerating, landfill among others.</p></li><li><p>Ing. Juan Jos Chvez</p><p>Waste Recovery and Disposal Codes</p><p>Waste related activities are classed as recovery (R) or disposal (D) as defined in the Waste Framework Directive (2006/12/EC). </p><p>...</p><p>...</p></li><li><p>Ing. Juan Jos Chvez</p><p>European Waste Catalogue</p><p>The European Waste Catalogue is a hierarchical list of waste descriptions, each given a code number.</p></li><li><p>Ing. Juan Jos Chvez</p><p>Philosophy of Waste Management</p><p>Avoidance or preventionMinimization or reduction</p><p>Reuse or recyclingMaterial recoveryEnergy recovery</p><p>IncinerationLandfill disposal</p><p>T H E OR Y</p><p>R E A L I T Y</p></li><li><p>Ing. Juan Jos Chvez</p><p>Examples of Waste Management</p><p> PET bottles</p></li><li><p>Ing. Juan Jos Chvez</p><p>Examples of Waste Management</p><p> Blackwaters or sewage</p></li><li><p>Ing. Juan Jos Chvez</p><p>Examples of Waste Management</p><p> 08 01 13 - Sludge from paint or varnishcontaining organic solvents or otherdangerous substances</p></li><li><p>Ing. Juan Jos Chvez</p><p>Examples of Waste Management</p><p> Automobile assembly plant</p><p>Industry08 01 13</p><p>15 01 01</p><p>15 01 02</p><p>16 01 22</p><p>19 08 12</p><p>Etc...</p><p>External waste management, contracts with competent and authorized waste companies</p><p>Internal waste management: Prevention, reduction and reuse policies; development of a waste separation strategy, improvement of the collection process. Analysis of material and energy recovery possibilities</p><p>Internal waste management:Sales from selected materials for its material or energy recovery</p></li><li><p>Ing. Juan Jos Chvez</p><p>Waste recovery</p><p>Waste recovery is the selective extraction of disposedmaterials for a specific next use, obtaining the maximumpractical benefits from products. It aims to reduce:</p><p> The consumption of fresh raw materials</p><p> Energy consumption </p><p> Air pollution</p><p> Water pollution </p><p> Material recovery</p><p> Energy recovery</p></li><li><p>Ing. Juan Jos Chvez</p><p>Material recovery of waste</p><p> Recycling: Process of turning selected waste products into new (recycled) products</p><p> Regeneration of organic and inorganic components (solvents, chemical substances, etc.)</p><p> Compost: Aerobic processes that transform organic waste into a fertilizer or soil amendment</p></li><li><p>Ing. Juan Jos Chvez</p><p>Energy recovery of wasteWaste-to-energy</p><p>Thermal technologies: Gasification (a set of chemical reactions that uses limited </p><p>oxygen to convert a carbon-containing feedstock into a synthetic gas, or syngas CO2 + CO + H2)</p><p> Pyrolysis (a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. For example, the bio-oils)</p><p> Thermal depolymerization Plasma arc gasification or plasma gasification process (PGP)</p><p>Biological technologies: Anaerobic digestion (Biogas CH4 + CO2) Fermentation (examples are ethanol, lactic acid, hydrogen) Other biological treatments</p></li><li><p>Ing. Juan Jos Chvez</p><p>Part 2: Anaerobic digestion</p></li><li><p>Ing. Juan Jos Chvez</p><p>Biological treatment processes</p><p> Aerobic treatment process: Biological processes that occur in the presence of oxygen. </p><p> Anaerobic treatment processes: Biological process that occur in the absence of oxygen. </p><p> Substrate: It is the term used to denote the organic matter or nutrients that are converted during biological treatment</p></li><li><p>Ing. Juan Jos Chvez</p><p>1. Energy contained in WW</p><p>2. Organic carbon contained in WW</p><p>Comparison of aerobic and anaerobic processes(Wastewater treatment processes)</p><p>ANAEROBIC AEROBIC</p><p>90 % biogas5 7 % synthesis of new biomass3 5 % losses</p><p>60 % synthesis of new biomass40 % losses</p><p>ANAEROBIC AEROBIC</p><p>95 % biogas (CH4 + CO2)5 % synthesis of new biomass</p><p>50 % CO250 % synthesis of new biomass</p></li><li><p>Ing. Juan Jos Chvez</p><p>Anaerobic digestion</p><p> Anaerobic digestion (AD) is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. </p><p> AD is often used for industrial or domestic purposes at managing waste. </p><p> This process yields a final product of mainly methane and carbon dioxide, a rich biogas suitable for energy production, widely used as a renewable energy. </p></li><li><p>Ing. Juan Jos Chvez</p><p>This degradation process can be divided up into four phases,named hydrolysis, acidogenesis, acetogenesis and methanation</p><p>Anaerobic digestion</p><p>Hydrolysis Acidogenesis Acetogenesis Methanogenesis</p><p>Carbohydrates</p><p>Fats</p><p>Proteins</p><p>Sugars</p><p>Fatty acids</p><p>Aminoacids</p><p>Alcohols</p><p>Acetic acid</p><p>CO2 , H2</p><p>CO2 , H2</p><p>Ammonia</p><p>BIOGASCH4 + CO2</p><p>H2S</p></li><li><p>Ing. Juan Jos Chvez</p><p>Applications of anaerobic digestion</p><p> Stabilization of sludge in WWTP</p><p> Treatment of industrial wastewaters</p><p> Landfill gas-to-energy</p><p> Biogas stations</p></li><li><p>Ing. Juan Jos Chvez</p><p>Applications of anaerobic digestion</p><p> Stabilization of sludge in WWTP</p></li><li><p>Ing. Juan Jos Chvez</p></li><li><p>Ing. Juan Jos Chvez</p></li><li><p>Ing. Juan Jos Chvez</p><p>Applications of anaerobic digestion</p><p> Treatment of industrial wastewaters</p></li><li><p>Ing. Juan Jos Chvez</p><p>Applications of anaerobic digestion</p><p> Landfill gas-to-energy</p></li><li><p>Ing. Juan Jos Chvez</p><p> Biogas stations</p><p>The main goal of biogas stations is to produce a certain quantity of biogas from determined organic substrates, in order to generate a stable and continuous amount of energy. </p><p>Applications of anaerobic digestion</p><p>Pre-treatmentAnaerobic digestion</p><p>SubstrateBiogas</p><p>Digestate</p></li><li><p>Ing. Juan Jos Chvez</p><p>Biogas stations</p><p> Substrates for biogas stations</p><p>The substrate and the efficiency of its conversion intobiogas are the factors that will determine the viabilityof the process.</p></li><li><p>Ing. Juan Jos Chvez</p></li><li><p>Ing. Juan Jos Chvez</p></li><li><p>Ing. Juan Jos Chvez</p><p>According to the solid content of the substrate:</p><p> Dry fermentation technology (when TS is greater than ~25%)</p><p>Types of biogas stations</p></li><li><p>Ing. Juan Jos Chvez</p><p>Anaerobic fermenters (PFR)</p></li><li><p>Ing. Juan Jos Chvez</p><p>Collectors of leachate or percolate for its recirculation into the sprinkling system</p></li><li><p>Ing. Juan Jos Chvez</p><p>Biogas holders</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process control </p></li><li><p>Ing. Juan Jos Chvez</p><p>Cogeneration unit (CHP)</p></li><li><p>Ing. Juan Jos Chvez</p><p>Types of biogas stations</p><p> Liquid or wet fermentation technology (TS less than ~15%)</p></li><li><p>Ing. Juan Jos Chvez</p><p>Part 3: Operation of a biogas station</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Temperature</p><p> pH-value (Hydrogen partial pressure)</p><p> Concentration of microorganisms (Retention time)</p><p> Inoculation and cultivation</p><p> Mixing (agitation)</p><p> Volume and organic load</p><p> Type of substrate (organic content and C/N/P ratio)</p><p> Presence or formation of inhibitors Flow recirculation and bypass</p><p> Biogas recirculation and removal</p><p> Specific surface of material (Mass transfer)</p><p> Redox potential</p><p> Etc...</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Temperature operational ranges Cryophilic (0 20 C) </p><p> Psychrophilic (20 30 C) </p><p> Mesophilic (30 40 C) </p><p> Thermophilic (40 60 C)</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> pH-value (Hydrogen partial pressure)</p><p>The measure of the acidity or basicity of the tank aqueous environment. The pH optimum of the methane - forming microorganism is at pH = 6.7 7.5.</p><p>Biogas digestion failure(Acid fermentation)</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Concentration of microorganisms (Retention time)</p><p>Methanogenic microorganisms have a long generation time in general. To avoid washing out of the reactor, hydraulic retention time must be at least 10-15 days with reactor systems which do not have facilities for retaining and returning biomass. Nevertheless, retention times are recommended to be of 50 days and more. In comparison with this, the regeneration times of hydrolytic and acid-forming bacteria are significantly shorter, so that with them there is hardly any risk of washout.</p><p>[days]</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Inoculation and cultivationThe start-up phase of an anaerobic plant often last 2-4 months. The cultivation of desired cultures of bacteria can fail completely, i.e., the anaerobic digestion doesnt take place and the biogas is not produced. To avoid these problems, the reactors are often inoculated with an anaerobic sludge from other fermentation process.</p><p>Hydrolytic b.</p><p>Methanogenic b.</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Volume and organic loading rateThe volume (organic) loading rate depends on several factors such temperature range of the process, organic dry-matter content in the substrate, retention time, dosing system, among others. Mostly, biogas digesters are designed to decompose 75% of the total degradable matter, due to economical and/or operational reasons.</p><p>OLR [kg VS.m-3.d-1], [kg COD.m</p><p>-3.d-1]</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Type of substrate</p><p> Dry matter and organic dry matter content</p><p>Terminology:Abb. SK* Meaning Units</p><p>DM - Dry matter content kg TS. ton SUBSTRATE-1 </p><p>oDM - Organic dry matter content kg VS. ton SUBSTRATE-1 </p><p>TS Xc Total solids (settable solids) g SAMPLE-1 </p><p>VS Xorg Volatile solids g VS. kg SAMPLE-1 </p><p>TSS Xc,WW* Total suspended solids (retained by a membrane filter)</p><p>g TSS. kg SAMPLE-1 </p><p>VSS Xorg,WW* Volatile suspended solids g VSS. kg SAMPLE-1 </p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Organic matter content and its measurementAbb. SK* Meaning Units</p><p>TOD TCHSK Theoretical oxygen demand Total oxidation Stoichiometric amount of O2 needed for a hypothetical total oxidation</p><p>mol O2 , g O2 </p><p>COD CHSK Chemical oxygen demand - OxidabilityIt is an oxygen equivalent of the organic matter that can be oxidized by using a strong chemical oxygen agent in acid solutions</p><p>mg COD . l SAMPLE-1 </p><p>BODx BSKx Biochemical oxygen demand - BiodegradabilityMeasurement of dissolved oxygen used by microorganisms for the biochemical oxidation of organic matter</p><p>mg BOD . l SAMPLE-1 </p><p>Correlation among measurements of organic content</p><p>TOD &gt; COD &gt; BODx</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Type of substrate</p><p> Organic matter content and its measurementAbb. Meaning Units</p><p>TOC Total organic carbonIt is a parameter that measures the composition of substrates (Firstly C and then C/H/O/N/P/S ratio). Organic carbon is oxidised to CO2 at high temperatures in the presence of catalysts.</p><p>mol C, g Cmol N, g Nmol O, g Oetc.</p><p>DOC Dissolved organic carbonIt is a parameter that measures the composition of dissolved organic compounds in aqueous solutions.</p><p>-</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Type of substrate Nitrogen content and its measurement</p><p>Abb. Meaning Units</p><p>NH4-N Ammonium nitrogen or total ammoniacal nitrogen (NH4+ + NH3) mg.l</p><p>-1</p><p>NH4+ Ammonium ion mg.l-1</p><p>NH3 Free ammonia or ammonia mg.l-1</p><p>NH3-N Ammonia nitrogen mg.l-1</p><p>Norg Kjeldahl nitrogen or organic nitrogen (Protein N and non-protein N e.g. urea, nucleic acids, polymers, etc.)</p><p>mg.l-1</p><p>TKN Total Kjeldahl nitrogen (= NH4-N + Norg) mg.l-1</p><p>NOx-N Total oxidised nitrogen (NO3-N + NO2-N) mg.l-1</p><p>NO3-N Nitrate nitrogen mg.l-1</p><p>NO2-N Nitrite nitrogen mg.l-1</p><p>TN Total nitrogen (sum of all nitrogen compounds) mg.l-1</p></li><li><p>Ing. Juan Jos Chvez</p><p>Process parameters</p><p> Type of substrate</p><p> Phosphorus content and its measurementAbb. Meaning Units</p><p>PO4-P Phosphate phosphorus, orthophosphate mg.l-1</p><p>Porg Phosphorus content of organic P compounds mg.l-1</p><p>TP Total phosphorus mg.l-1</p><p>complex P Complex bonded P, that cannot be precipitated with chemicals mg.l-1</p></li><li><p>Ing. Juan Jos Chvez</p><p>Part 4: Modelling at laboratory</p></li><li><p>Ing. Juan Jos Chvez</p><p>Laboratory bioreactors</p><p>Characteristics of our reactors: CSTR model</p><p> Semi-continuous feeding</p><p> Single-stage anaerobic digestion</p><p> Mesophilic conditions (37oC)</p><p> Inoculum: Stabilized excess sludge from WWTP</p><p> TS of reactors sludge is less than 15%</p><p> OLR of reactor is less than 3 gVS.L-1.d-1</p></li><li><p>Ing. Juan Jos Chvez</p><p>Dry matter and organic dry matter content</p><p> Dry matter (DM)</p><p> Organic dry matter (oDM)</p><p> Loss on ignition (LOI)</p><p>Laboratory oven(105oC, 6 h)</p><p>Laboratory furnace(105oC, 3 h)</p><p>Analytical balance</p></li><li><p>Ing. Juan Jos Chvez</p><p>Dry matter and organic dry matter content</p><p>Gravimetric method:</p><p>Calculation Units</p><p>DM = (md-me)/(ma-me) . 1000 g TS/kg sample or %</p><p>iDM = (mb-me)/(ma-me) . 1000 g IS/kg sample or %</p><p>oDM = DM - iDM g VS/kg sample or %</p><p>LOI = oDM/DM . 100 %</p><p>e = empty a = added d = driedb = burnt</p><p>DM = Dry matteroDM = organic dry matteriDM = inorganic dry matterLOI Loss on ignition</p><p>TS Total solidsVS Volatile suspended solidsIS inorganic suspended solids</p></li><li><p>Ing. Juan Jos Chvez</p><p> Calculate TS, VS, LOI1. Maize silage</p><p>me = 100,252 g</p><p>ma = 101,586 g</p><p>md = 100,819 g</p><p>mb = 100,325 g</p><p>2. Poultry manureme = 50,125 g</p><p>ma = 55,155 g</p><p>md = 51,131 g</p><p>mb = 50,438 g</p><p>Dry matter and organic dry matter contentExercises</p><p>Literature says: Maize silage has a DM = 20-40 % and a oDM = 95%.DM (LOI) Poultry manure has a DM = 10-29 % and a oDM = 70%.DM (LOI)</p></li><li><p>Ing. Juan Jos Chvez</p><p>Organic loading rate of reactor</p><p>Organic loading rate (OLR) means how much organic matter is being introduced into the reactor in an interval of time. </p><p>For this purpose, we can use either the COD or the VS parameter.</p><p>OLRCOD = Vsubstrate.CODsubstrate/Vsludge</p><p>OLRVS = substrate.VSsubstrate/Vsludge</p></li><li><p>Ing. Juan Jos Chvez</p><p>Organic loading rate of reactorExercises</p><p> Calculate the amount of substrate that have to be loaded into the biogas plant.1. Maize silage</p><p> OLR = 3 kg VS.m-3.d-1</p><p> Vdigester = 3 000 m3 (The digester is filled with sludge at its 85% </p><p>capacity)</p><p>2. Po...</p></li></ul>