biomass & biofuels anareobic digestion
DESCRIPTION
Biomass & Biofuels Anareobic Digestion. San Jose State University FX Rongère March 2009. Biochemical Conversion. Thermochemical Conversion. Extraction. Anaerobic Digestion. Fermentation. Direct Combustion. Gasification. Pyrolysis Liquefaction. Steam. Gas. Oil. Charcoal. Biogas. - PowerPoint PPT PresentationTRANSCRIPT
Biomass & BiofuelsAnareobic Digestion
San Jose State University
FX RongèreMarch 2009
Biofuels
Biofuels cover a broad range of technologies and applications:
Thermochemical Conversion
Direct Combustion
Direct Combustion
Gasification
Gasification
PyrolysisLiquefaction
PyrolysisLiquefaction
Biochemical Conversion
Anaerobic Digestion
Anaerobic Digestion
Fermentation
Fermentation
Extraction
Extraction
Heat Electricity Transportation
Steam Gas Oil Charcoal Bio-dieselBiogas Ethanol
Source: From Boyle, Renewable Energy, 2nd edition, 2004
Anaerobic Digestion Breakdown of biodegradable material by micro-
organisms (bacteria) in absence of gaseous oxygen It applies to 3 different waste treatments:
Landfill Animal waste – Manure Waste water treatment
It generates a biogas composed of:Matter %
Methane, CH4 50-75
Carbon dioxide, CO2 25-50
Nitrogen, N2 0-10
Hydrogen, H2 0-1
Hydrogen sulphide, H2S 0-3
Oxygen, O2 0-2
Anaerobic Digestion
The process includes 4 major biological or chemical stages:
Carbohydrates
Polymer base on Glucose molecule C6H12O6
α-D-glucopyranoseMono-mere
CellulosePoly-mere
Carbohydrates
Proteins:
C — CO — H
O
—
NH2
H
R — N — C — C
O
H H
R’
peptide bond
Carboxyl GroupAmino Group
Example of a protein structure:Myoglobin
Carbohydrates
Fats:Polymers of fatty acids and alcohols
O
C
H — CH — CH — CH — H
O
R
O
C
O
R
O
C
O
RFatty acids
Alcohols
Hydrolysis Converts Complex organic matters (Carbohydrates,
Proteins and fats) in Soluble organic molecules (Sugar, Amino-acids, Fatty acids)
Sugar - Glucose
R — C
O — H
O
Fatty Acids
N — C — C
O — H
O
R
H
H
Amino Acids
Fermentation - Acidogenesis
Decomposition in volatile Fatty Acids (C3 and C4), acetic acid and H2
CH3 — C
O — H
O
ethanoic acid(acetic acid / vinegar)
propionic acid
CH3 — CH2 — C
O — H
O
O — H
butanonic acid(butyric acid)
CH3 — CH2 — CH2 — C
O
Acetogenesis
Conversion of the volatile fatty acids in acetic acid and H2
Bacteria syntrophic (mutually beneficial) with the methanogens
Acetic Acid
Methanogenesis
Acetotrophic methanogens2 CH3COOH 2 CO2 + H2
Methylotrophic methanogens4 CH3OH + 6 H2 3 CH4 + 2 H2O
Hydrogenotrophic methanogensCO2 + 4 H2 CH4 + 2 H2O
CH3COOH CO + CH3OH
Matter %Methane, CH4 50-75
Carbon dioxide, CO2 25-50
Nitrogen, N2 0-10
Hydrogen, H2 0-1Hydrogen
sulphide, H2S 0-3
Oxygen, O2 0-2Resulting Biogas
Anaerobic digestion drawbacks
Bacterias are sensitive to: Oxygen Temperature (35o optimal - Mesophilic) pH (stability and slightly acidic) Toxic component (H2S, NH3, metals)
Optimization and control of an anaerobic bio-digestor are complex
Takes time (several days to several years)
Municipal Solid Waste
MSW production in the USA
Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2005
EuropeJapan
Domestic waste sources in the USA
Municipal Solid Waste
Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2005
Landfill
MSW treatment in the USA
Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2005
Landfill/Recovery/Combustion in the USA
Recovery-Combustion-Landfill ratio evolution from 1960 to 2005
0%
20%
40%
60%
80%
100%
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year
Landfill
Recovery
Combustion
Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2005
Landfill
MSW treatment in the world
Source: Kai Sipilä, VTT Processes, Finland MUNICIPAL AND COMMERCIAL SOLID WASTE FOR PYROLYSIS (OILS ) AND GASIFICATION MARKETS 2002
1995
Landfill
Structure of a modern landfill
Landfill
Biogas is used to generate electricity or is sold to utilities
Major issues: Pollutants: Siloxanes, SO2, Solanes, Aliphatics
components, explosive cycloalcnes CH4 content variation
Internal Combustion Engine
Diesel cycle
inW
P1
P2
V1 V2
Pressure
Volume
outW
combQ
inout hhm
.
Methane
CH4
Energy Content: 802 kJ/mol=50,125 kj/kg
Methane Combustion:CH4+2 O2 -> CO2 + 2 H2O
Stoichiometry: 17.4 Auto-ignition temperature: 537°C Adiabatic Flame Temperature: 1,950°C Explosive limits: 5–15%
Diesel Cycle
Adiabatic Compression
AA
AA
Closed
WQdt
dE
A A
A
Closed T
Q
dt
dS
P
dPR
T
dTCpds
dTCpdh
dTRCpdTCvdu
..
.
).(.
Air is close to an ideal gas:
),(
),(
).(.
TPss
TPuu
kuMeME
Perfect compressor
Compression ratio Compression ratio
Is determined by the methane auto-ignition temperature: 537oC
1
2
P
Pr
1
1
1
2
112 ..
rT
P
PTT
40r
Constant pressure Combustion
Max temperature is limited by the materials typically 1,200oC
AA
AA
Closed
WQdt
dE
A A
A
Closed T
Q
dt
dS
Perfect transfer
12. VVPW F VF is the volume at
the end of the combustion
A part of the power is generated during the combustion phase
4.0 5.0 6.0 7.00
500
1000
1500
2000
s [kJ/kg-K]
h [
kJ
/kg
]
1 bar
40 bar
10 bar Air
Diesel Cycle
Adiabatic Expansion (similar to the compression)
AA
AA
Closed
WQdt
dE
A A
A
Closed T
Q
dt
dS
Venting pressure is not equal to P1. It is defined by the expansion to V2
Conversion rate of a Diesel cycle is about 40%. Venting temperature of 400oC allows cogeneration
Advantages/Disadvantages
Engine Advantages Disadvantages
Internal Combustion Engines
EfficiencyCostMaturity
Sensitive to CH4 concentration and pollutants (Siloxanes and silanes)Maintenance costPollutions (NOx, SOx)
Stirling Engines
Low MaintenanceNo compression requiredAccept CH4 variationLess pollution
New technologyComplexity
Gas Turbines
Low MaintenanceAccept CH4 variationLess pollution
CostEfficiency without recuperation
Other Engines
Stirling Engines
Other Engines Gas turbines
50 30 kW Capstone microturbines convert flare gas at Lopez Canyon Landfill in Sylmar, CA for 1.5 MW
20 30 kW Capstone microturbines convert flare gas at in La Ciotat, France
Liquefied Natural Gas Generation
Prometheus generates Liquefied Natural Gas from landfill biogas.
California MSW 70 MM tons per year of
MSW generation leading to 11 lb/day/capita (more than 2 times the USA average)
43 MM tons are sent to landfills (61% of total MSW), thermal conversion is about 20% of total MSW
There are three MSW mass-burn for 67 MWe and 46 landfill gas to energy facilities (LFGTE) for 280 MW
Spittelau incineration plant in Vienna.
Potential: .15 to .45 m3 of biogas/kg Biogas = 60% methane 1,800 MM Therm/y 21 TWh/y Electricity 2.8 GW
MSW Component and properties
* Ash: proportion of non burning residues† HHV: Higher Heating Value, energy content for combustion in absence of water
Direct Combustion potential: 4,000 MMTherm/y, 30 TWh/y, 4.1 GWSource: CEC-500-2006-095
Manure bio gas
Potential in California
California is the first state of the USA for dairies
California
Dairies 1.7 Millions cows 2,153 dairies (2002)
5 leading counties Tulare Merced Stanislaus San Bernadino King
Potential is: 2.4kWh/day/cow (assuming 20% used for digester heating, conversion rate:30%) 170 MM Therms/y, 1,500 GWh/y, 200 MW
Process
Digestion duration: 15-20 days
Temperature: 36oC
Energy in Dairies
Electric Energy Use on a Representative California Dairy Farm
Water Systems8%
Air Circulation10% Lighting
13%Compressed Air
4%
Milk Cooling27%
Miscellaneous2%
Waste Handling24%
Milk Harvest12%
Wide variation: 300 – 1,500
kWh/cow/y1
Narrower interval: 700 – 900
kWh/cow/y2,5
Total California: 1,190 GWh/y3
SCE guide - 2004
1: SCE guide – 20042: Audit PG&E3: A Consumer’s Look at California’s Dairy Industry - 20024: PG&E electricity bills – 2004 (Livestock)5: Scott Sanford University of Wisconsin (Wisconsin data)
Using digesters, California dairies may be energy neutral
Examples Biogas by-products can be used by microturbines for on-site
energy use, such as at this Wisconsin wastewater treatment plant
Digesting tanks at Microgy, Inc.'s biogas plant process manure from about 10,000 cows into methane and compost. Credit: Microgy, Inc.
Types of Anaerobic Digesters
There are many different types of digesters: Covered lagoons Complete mix digesters
Complete Stirred Tank Reactors (CSTR)Completely Mixed Flow Reactors (CMF)Continuous Flow Stirred Tank (CFST)
Plug flow digesters Anaerobic Sequencing Batch Reactor Fixed film digesters
Covered Lagoons
Advantages Low cost (relative) Low tech / easy to
construct
Disadvantages Cover maintenance / life Large footprint Solids / nutrient
accumulation
Complete Mix Digesters
Advantages High level of experience Works over wide range of influent Total Solids (TS) Can be used with scrape or flush systems and
swine or dairy systems
Disadvantages Poor biomass immobilization Mechanical mixing requirement
Plug Flow Digesters
Advantages Good track record with Dairy manure Works well with scrape systems
Disadvantages Requires high solids manure (11 - 14 %) Not compatible with sand bedding
Haubenschild Farm
750 cow dairy in Minnesota 59,500 pounds of milk per day Plug-flow manure digester:
130'LX30'WX14'D 1/2 million gallons 20,000 gallons each day constant 100F degrees 72,500 cf of biogas per day Biogas is 60% methane & 35% CO2
Electric generator: 150kW diesel cycle generator Waste heat recovery for digester operation and
building heat
Haubenschild Farm
Cost Analysis
Source: C. Nelson, J. Lamb Final Report: Haubenschild Farms Anaerobic Digester The Minnesota Project Aug. 2002
Revenues
yearsk
kSP 2.4
85$
355$
Simple Payback:
Internal Rate of return:Horizon: 20 years
0
1
20
1
t
tt
IRR
RCostNPG
IRR=23%
Other animals
California farm animal population
Source: CEC-500-2006-095
Companies to follow
Capstone www.capstone.com STM-bio Prometheus-Energy
www.prometheus-energy.com RealEnergy www.realenergy.com Cummins www.cummins.com Solar www.mysolar.cat.com Microgy
www.environmentalpower.com/companies/microgy/