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merupakan copy dari materi presentasi "Biomethanation of Municipal Solid Waste"

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  • BIOMETHANATION

    OF

    MUNICIPAL SOLID WASTE

    Presented by,

    Salin Kumar Sasi

  • URBAN WASTE SCENARIO

    Urban India generates about 1.4 lakh MT/day of MSW

    Requires 1750 acres of land for land filling/year

    Courtesy-MNRE

  • PHASES

    PHASE I MSW SCENARIO IN INDIA

    PHASE II BIOMETHANATION

    PHASE III FACTORS AFFECTING

    BIOMETHANATION

    PHASE IV BIOMETHANATION PROCESS

    PHASE V BIOMETHANATION OF MSW IN INDIA

    PHASE VI BIOMETHANATION PLANT IN

    ABROAD AND INDIA

    PHASE VII RESULTS AND DISCUSSIONS

  • PHASE I

    MSW SCENARIO IN INDIA

  • Courtesy-MNRE

  • TECHNOLOGICAL OPTIONS FOR

    ENERGY RECOVERY FROM URBAN WASTES

  • Courtesy-MNRE

  • Courtesy-MNRE

  • POTENTIAL OF ENERGY FROM

    URBAN WASTES

    2007 2017

    MSW

    (lakh tpd)1.48 2.15 3.03

    MW 2550 3670 5200

    MLW

    (mcd)17.75 20.70 24.75

    MW 330 390 460

    2012

    Courtesy-MNRE

  • INDIAN SCENARIO

    As per MSW Rule 2000, biodegradable material

    should not be deposited in the sanitary landfill

    Therefore there is almost no scope of generation of

    biogas in the form of landfill gas from new sanitary

    landfills

    However, there is a huge potential of trapping the

    landfill gas generated in the old dump-sites across

    the country, particularly the large ones with more

    than 5 meter thickness (height plus depth)

    Courtesy-MNES

  • Courtesy-NEERI

  • WTE TECHNOLOGIES

    Bio-methanation

    Incineration

    RDF

    Gasification

    Integrated systems

  • MERITS OF BIOMETHANATION

    Reduction in land requirement for MSW disposal.

    Preservation of environmental quality.

    Production of stabilized sludge can be used as

    soil conditioner in the agricultural field.

    Energy generation which will reduce operational

    cost.

    Supplement national actions to achieve real, long

    term, measurable and cost effective GHGs

    reductions in accordance with Kyoto Protocol.

  • PHASE II

    BIOMETHANATION

  • Courtesy-MNRE

  • PRINCIPLES

    Complex process leading to generation of methane and carbon dioxide.

    Process involves three steps (Barlaz et al 1990) Hydrolysis Acidification Methanogenesis

    Process can be carried out in Single step Two step

  • HYDROLYSIS

    Anaerobic bacteria breakdown complex organic molecules (proteins, cellulose, lignin and lipids) into soluble monomer molecules such as amino acids, glucose, fatty acids and glycerol.

    Monomers are available to the next group of bacteria.

    Hydrolysis of complex molecules is catalyzed by extra cellular enzymes (cellulose, proteases and lipases).

    Hydrolytic phase is relatively slow ,can be limiting in anaerobic digestion.

  • ACIDOGENESIS

    Acidogenic bacteria converts sugar, aminoacids and fatty acids to organic acids (acetic, propionic, formic, lactic, butyric acids), alcohols and ketones (ethanol, methanol, glycerol and acetone), acetate, CO2and H2.

    Acetate is the main product of carbohydrate fermentation.

    The products formed vary with type of bacteria as well as with the culture conditions (temperature, pH etc).

  • ACETOGENESIS

    Acetogenic bacteria converts fatty acids and alcohols into acetate, hydrogen and carbon dioxide .

    Acetogenic bacteria requires low hydrogen for fatty acids conversion .

    Under relatively high hydrogen partial pressure, acetate formation is reduced and the substrate is converted to propionic acid, butyric acid and ethanol rather than methane.

  • METHANOGENESIS

    Methanogenesis in microbes is a form of anaerobic respiration.

    Methanogens do not use oxygen to breathe, oxygen inhibits the growth of methanogens.

    Terminal electron acceptor in methanogenesis is carbon.

    Two best described pathways involve the use of carbon dioxide and acetic acid as terminal electron acceptors:

    CO2+ 4 H2 CH4 + 2H2O

    CH3COOH CH4 + CO2

  • Acetate

    Short chain fatty acids

    Lipase, protease, pectinase

    cellulase, amylase produced

    by hydrolytic microorganisms

    Stage 1 Hydrolysis

    Organic matter

    (Carbohydrates, lipids, proteins etc)

    Stage 2 Acidogenesis

    (mainly acetic and formic acid)Stage 3 Acetogenesis

    Acetate CO2 and H2

    Methane +CO2

    -oxidation, glycolysis

    deamination, ring reduction

    and ring cleavage

    Carboxylic volatile acids, keto acids,

    hyroxy acids, ketones, alcohols,

    simple sugars, amino aicds,H2 and CO2

    Stage 4 Methanogenesis

    Courtesy-Kashyap .D.R et al ,2003

  • PHASE - III

    FACTORS AFFECTING

    BIOMETHANATION

  • Courtesy-MNRE

  • NUTRIENTS

    Lower nutrient requirement compared to aerobic bacteria.

    COD:N range is 700:5.

    N used in synthesis of Enzymes, RNA, DNA.

    Concentration of various nutrients (Speece et. al ,1996)

    N : 50 mg/lP : 10 mg/lS : 5 mg/l

  • pH

    Most important process control parameter.

    Optimum pH between 6.7 & 7.4 range for methanogenic bacteria (Zehnder et. al. 1982).

    Excess alkalinity or ability to control pH must be present to guard against the accumulation of excess volatile acids.

    The three major sources of the alkalinity are lime, Sodium bicarbonate and sodium hydroxide.

  • TEMPERATURE

    Constant and Uniform temperature maintenance.

    Three temperature range

    Psychrophilic range ; < 200 C.

    Mesopholic range ; 200 C to 400C.

    Thermophilic range ; >400 C.

    Rates of methane production double for each 100C temperature change in the mesophilic range .

    Loading rates must decrease as temperature decreases to maintain the same extent of treatment.

    Operation in the thermophilic range is not practical because of the high heating energy requirement (Ronald L. Drostle 1997)

  • Study of temperature variation (Alvarez Rene et al 2007).

    Forced square-wave temperature variations

    (i) 11 0 C and 25 0 C,

    (ii) 15 0 C and 29 0 C,

    (iii) 19 0 C and 32 0C.

    Large cyclic variations in the rate of gas production

    and the methane content.

    The values for volumetric biogas production rate and

    methane yield increased at higher temperatures.

    The average volumetric biogas production rate for

    cyclic operation between 11 and 25 0C was 0.22 L d -1 L -

    1 with a yield of 0.07 m 3CH 4kg -1 VS added (VSadd)

  • Between 15 and 29 0C the volumetric biogas

    production rate increased by 25% (to 0.27 L d -1L-1with

    a yield of 0.08 m 3CH 4 kg -1 VSadd).

    Between 19 and 32 0C, 7% in biogas production was

    found and the methane yield was 0.089 m3 CH4 kg-1

    VSadd.

    Digester showed an immediate response when the

    temperature was elevated, which indicates a well-

    maintained metabolic capacity of the methanogenic

    bacteria during the period of low temperature.

    Periodic temperature variations appear to give less

    decrease in process performance than as prior

    anticipated.

  • Courtesy- Alvarez Rene et al 2007

  • SOLID RETENTION TIME (SRT) AND

    HYDRAULIC RETENTION TIME(HRT)

    SRT is defined as the average time the solid particles

    remains in the reactor.

    The anaerobic digestion is typically performed in

    Continuously Stirred Tank Reactor (CSTR).

    The performance of CSTR is dependent on hydraulic

    retention time (HRT) of the substrate and the degree of

    contact between the incoming substrate and a viable

    bacterial population (Karim et al.,2005).

    An increase or decrease in SRT results in an increase or

    decrease of the reaction extent.

  • MIXING

    Mixing creates a homogeneous substrate preventing

    stratification and formation of a surface crust, and

    ensures solids remain in suspension.

    Mixing enables heat transfer and particle size reduction

    as digestion progresses .

    Mixing can be performed in two different ways(Kaparaju

    P et al,2007):

    Continuous mixing SRT is equal to HRT

    Non-continuous mixing SRT is more than HRT

  • The effect of continuous , minimal (mixing for 10 min

    prior to extraction / feeding) and intermittent mixing

    (withholding mixing for 2 hr prior to extraction/feeding)

    on methane production was investigated in lab-scale

    CSTR (kaparaju P. et. al ,2007) .

    On comparison to continuous mixing, intermittent and

    minimal mixing strategies improved methane

    productions by 1.3% and 12.5%, respectively.

  • ALKALINITY

    Calcium, magnesium, and ammonium

    bicarbonate are examples of buffering substances

    found in a digester .

    A well established digester has a total alkalinity

    of 2000 to 5000 mg/L.

    The principal consumer of alkalinity in a reactor

    is carbon dioxide .

  • TOXICITY

    Toxicity depends upon the nature of the substance

    , concentration and acclimatization .

    NH 4-N concentration of 1500-3000 mg/L at 200C

    and pH 7.4 and above is considered stimulatory .

    Anaerobic process is highly sensitive to toxicants

    due to slow growth rate.

  • PHASE-IV

    BIOMETHANATION PROCESS

  • Courtesy-MNRE

  • BIOMETHANATION INCLUDES FOUR

    MAJOR ELEMENTS

    1. Pretreatment.

    2. Digest

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