Post on 28-Dec-2015
Examples of Renewable Biofuel Processes being researched at Murdoch University:
1.DiCOM: Turning Solid Municipal Waste to Energy and Compost
2.Milking Algae: Energy efficient harvesting idea.
3.Second generation bioethanol: Instead of using food material (sugar based) using waste cellulosic material
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DiCOM Process
Municipal Solid Waste (MSW) in Australia
Yearly Waste generation 6.5 Mt/year
Average Waste disposal costs ($/t) 74 $/t
Potential income to waste treatment
facilities 481 M$
Treatment of the Organic Fraction of Municipal Solid Waste (MSW)
Food waste, paper, garden waste etc.
Historically – incineration or landfill
Lost public support• Ground water – leachate
• Atmosphere – green house gases (CH4, N2O)• Odour emission
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• Traditional Landfill
Unlined Landfill
Sanitary Landfill
Landifill site being lined
Landfill leachate
Organic Waste Treatment- Composting
Simple aerobic processConverts putrescible organic waste into humus rich,
hygienic productProblems:
• Odour caused by raw material exposed to open air• Vermin• Greenhouse gas emission (CH4, N2O)
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Treatment Options of the “Organic” Fraction of MSW
Aerobic Composting Large land areas are neededOdor and Leachate emissionVermin and pathogen problemsCH4 emission (20 x GHG)
Anaerobic DigestionSlow as a batch processProblems with Endproduct stabilityProblems with Process stability (acidification)
Why not combination of both ?Has been trialed (handling, cost problems)Digestion and Composting in one vesssel?
• Composting of solid waste
Introduction:
Organic Waste Treatment - Anaerobic Digestion
An Oxygen Free process
Produces biogas (mixture of CH4 and CO2)• Can be used for power generation• Makes the process more economical and sustainable
Problems:• End product not suitable for direct land application (high levels of organic acids, NH3)
• Thermophilic digestion unstable due to acidification
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WaterCorpWoodman Pt.Plant, Perth
Anaerobic
Digestion
Of Solid Waste
Anaerobic Digestion and Composting in one vessel?
Conceptual barriers of acceptance:
Aerobic bacteria require oxygen.
Strictly anaerobic bacteria (e.g. methane producers) are highly oxygen sensitve.
Can one rely on “facultative anaerobes”?
From initial microbiology point of view: compatibility concerns
Approach
Laboratory Set-Up of DiCom process
Online monitoring of:pH, Eh, oxygen, hydrogen, CO2, CH4,
Control of cycles, ORT- pat.air supply, mixing
DiCOM pilot plant built by ORT
Methods and Approaches used• Develop and operate a computer controlled laboratory digester
• Radio-isotope studies showed which pathway the bacteria
chose
• Molecular Biology Analysis (TRFLP) and Pure Culture
Techniques
• Compost stability tests and Potting trials
• Pilot scale test runs
• Biological toxity tests (ammonia, plant pathogens)
• Developing a mathematical model…PhD candidate involved inALL work at the ANAECOpilot plant
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Reactor Run Time (days)
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An aerobic process
Microbes use oxygen in the air to degrade organic matter
Products: Carbon Dioxide (CO2) + HEAT
Composting Overview:
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Organic Waste Treatment – Hybrid Process
Combined composting and anaerobic digestion
The DiCOM® Process is one such process
Developed and Patented by the Western Australian Company Anaeco
(anaeco.com.au)
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Developed and patented by Anaeco
19 day duration
Hybrid process combining aerobic composting with high temperature (thermophilic) anaerobic (no air) digestion
Treats Organic Municipal Solid Waste (MSW) stable compost
What is the DiCOM® Process?
Aerobic and methanogenic (strictly anaerobes) are typically mutually exclusive.
Aerobes need oxygen while methanogens are believed to be killed by oxygen
Also, once killed the methanogens only regrow very slowly as they require highly reduced conditions and grow slowly (doubling times of days)
DiCOM® Process challenges microbiological concepts
Air
CO2
20°C
60°C
Phase 15 Days
SortedRubbish
The DiCOM® Process
Organics + O2 Carbon Dioxide (CO2)
Aerobic microbial activity
Air
CO2
Air
Biogas
VFA = Volatile Fatty Acids (Acetate, Butyrate, Propionate)
Anaerobic Liquid
60°C
Heater
Phase 15 Days
Phase 27 Days
55°C
X
SortedRubbish
The DiCOM® Process
Fermentation CO2 + VFA VFA CH4 & CO2 (biogas)
(methanogens)
Air
CO2
Air
Biogas
Anaerobic Liquid
60°C
Heater
Air
CO2
Anaerobic Liquid
35°C
Phase 15 Days
Phase 27 Days
Phase 37 Days
55°C
X
CompostSortedRubbish
The DiCOM® Process
The DiCOM process starts with an aerobic phase (1) in which initial composting heats up the reactor to thermophilic conditions.
The heated reactor is then flooded to undergo thermophilic anaerobic digestion.
To remove any odors and organic products (e.g. fatty acids) that can cause instability a final aerobic treatment is carried out
All three steps are in the same enclosed reactor, requiring no handling and limiting gaseous and liquid emissions.
Reactor 1
Reactor 3
Reactor 2
Fill &Initial Aeration
StartAnaerobic(No Air)
Anaerobic(No Air)
Direct TransferOf Anaerobic Liquid
FinishAnaerobic(No Air)
DiCOM® Commercial Plant Structure
Final Aeration& Empty
Final Aeration& Empty
Fill &Initial Aeration
Anaerobic(No Air)
Phase 1Phase 2Phase 3
Phase 1Phase 2Phase 3
Phase 1Phase 2Phase 3
Using 3 identical reactors with rotating phases. Drain reactor that completed digestionTransfer liquor transferred to next digestion reactor.
This also provides a strong start-up inoculum.
Buffer capacity
This liquor recylce minimises water consumption and allows cross inocculation of the reactors.
Laboratory reactor of twin highly computerised, twin reactors carrying out theDiCOM process at Murdoch University, Perth.
DiCOM® Pilot Plant
Western Metropolitan Regional Council (WMRC)
• Established in 1989
• 5 member Councils.
― Town of Mosman Park
― Shire of Peppermint Grove
― Town of Cottesloe
― Town of Claremont
― City of Subiaco
Western Metropolitan Regional Council (WMRC)
• Waste management sole responsibility
• Population served: 45,000
• Area: 22km2
Staged Approach to Project Delivery
• Stage 1
• Demonstrate performance
• Single DiCOM Bioreactor
• Waste sorting capability
• Full community support
• Capacity:18,500tpa
• Stage 2
• Increase capacity
• 2 additional DiCOM Bioreactors
• Waste sorting and recyclables recovery
• Capacity 55,000tpa
pHProbe
EhProbe
H2Probe
SamplingPort
HeatExchange Unit
CirculationPump
PressureTransducer
Valve
Gas VolumeAnalyser
SolenoidValve
DO Probe
NH3Trap
CO2Trap
TempProbe
CoreTemperature
Probe
Insulated Reactor
Screen
GasAnalyser
Valve
LiquidEntry/Drain
Air FlowMeter
SolenoidValve
Air In
Reactor Design
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pH
Acetate Butyrate Acetate 2 Butyrate 2 pH
Transfer of active anaerobic culture reduces VFA accumulation (open symbols)
Volatile Fatty Acid (VFA) Profile
Electron Balance
During aeration …
Rubbish
O2 CO2
Every O2 used accepts 4 electrons
Electron
Carbon
Oxygen
Electron Balance
During the absence of oxygen …
Rubbish
Methanogen
Electron
Carbon
Hydrogen
Electron Balance
During the absence of oxygen …
Rubbish
CH4
Every CH4 contains 8 electronsAfter Lee Walker
Methanogen
Electron
Carbon
Hydrogen
Air
Exit Gas
Air
Biogas
Anaerobic Liquid
60°C
Heater
AirAnaerobic
Liquid
35°C
Phase 1 Phase 2 Phase 3
55°C
X
The DiCOM® Process
20°C
Monitor O2O2CH4
O2 O2
Exit Gas
To O2To O2To CH4
Effect of Process Optimisation on Total “Electron Flow in DiCOM® process: 50% more biogasHow about other bio-fuels from Cellulose Waste?
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Optimised
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Aerobic AerobicAnaerobic
50% increase in degradation during the anaerobic phase
Electron Equivalents
CO2 CH4
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Electron Flow For Aerobic/Anaerobic Treatments:
DiCOM®
Full Composting
Full Anaerobic
Low e- flow composting days 12-19 suggests stability Rate of e- flow is enhanced when the solid is flooded with anaerobic
inoculum/liquid Solid degradation rate is greater during thermophilic anaerobic
digestion
Low e- flow during anaerobic corresponds with VFA exhaustion
Direct transfer of anaerobic liquid is beneficial
Provided more rapid onset of biogas (and methane) production
Provided greater biogas production
Reduces the accumulation of VFA’s
Electron flow showed that a greater amount of degradation was channelled into fuel (biogas) production
Provides an economical advantage
Conclusion
DiCOM Take home messages: (the material is supposed to serve as examples that students can use if asked in an exam)
•Combination of aerobic and anaerobic processes is possible (as shown for Simultaneous nitrification and denitrification).
•In batch processes something similar to biomass retention can be used by direct transfer of inoculum from a sister reactor.
•The overall degradation performance between aerobic and anaerobic processing can be recorded online by transferring oxygen uptake rates (*4) and methane production rates (*8) into electrons (energy) removed from the organic waste
•Advanced process control needed to prevent the acidification of the reactor
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Hydrolysis
Fermentation
Can we choose which product we want?
• Organic acids and CH4 are natural, low-tech processes• Ethanol and H2 require advanced process control and
product removal.• Highest demand: ethanol
Waste Cellulose
Sugars
Ethanol Organic Acids
H2 CH4 Electricity
Hydrolysis
Fermentation
Isn’t Ethanol old and easy technology (natural fermentation)?
• From starch and sugar: yes, from waste cellulose: no.
• Ethanol from food crops not considered to be sustainable
and quantitatively sufficient
• New Breakthroughs?
Waste Cellulose
Sugars
Ethanol Organic Acids
H2 CH4 Electricity
Biological (enzymatic hydrolysis of cellulose become industrially feasible, IOGEN, Canada) Simultaneous Saccharification/ Fermentation
Hydrolysis
Fermentation
Waste Cellulose
Sugars
Ethanol Organic Acids
H2 CH4 Electricity
SSF
Simultaneous saccharification / fermentation addresses
problem of sugars inhibiting hydrolysis. More R& D needed.
Simultaneous SSF and Distillation?
Approach needed: process integration
Distillation
Bio-ethanol from cellulosic waste
First Generation Bio-ethanol(the material is supposed to serve as examples that students can use if asked in an exam)
•Production of Ethanol from sugar cane, corn and other food crops.
•While the process still requires significant energy input for distillation and growth of crops (fertilisers, water, etc.), it has some success in Brazil as a transport fuel.
•However as the proposed large scale production in the US around 2006/7 has resulted in increases in prices of the raw material and as a result also in other foods (e.g. beef, and even rice), it has been seen as very controversial.
•A second generation Biofuel, not competing with food or arable land (and ideally not with water) is being investigated world wide. It is based on largely non edible organics such as straw, paper, etc. and termed cellulosic wastes.
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Second Generation Bio-ethanol from cellulosic wastes(the material is supposed to serve as examples that students can use if asked in an exam)
•While the calorific value of cellulose is similar to that of sugar it is a lot harder to degrade requiring slowly acting cellulase enzymes.•The enzymes are typically produced by fungi such as Trichoderma•This is an aerobic process in which the fungi grow on cellulosic material•Either the enzyme needs to be costly extracted and then made available to hydrolyse cellulose enzymatically in the presence of yeasts (simultaneous saccharification and fermentation) or•an aerobic (production of fungus and enzyme) / anaerobic (fermentation of sugars to ethanol by the yeast) system can be conceptualise which could make Cellulosic bioethanol more sustainable.•Take home message: another example of integrating aerobic and anaerobic processes
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Milking Algae Concept
Traditional way of growing algae for oil(the material is supposed to serve as examples that students can use if asked in an exam)
•Advantage of traditional algal biofuel production:•higher efficiency than terrestrial plants•not competing with food production•not competing with arable land use
•Problems of extracting algal oil:•Slow growth of algae•High nutrient requirements (N, P, etc.) being costly•High levels of dead algal cells as waste product•High energy costs of drying algae and extracting oil
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Milking Algae as an alternative idea(the material is supposed to serve as examples that students can use if asked in an exam)
•Some algae contain > 50% of oil.
•If the oil could be removed without killing the algae, then the algae could be re-used to produce more oil (analogy to milking the cow insteady of killing the cow and extracting milk from the dead cow)
Advantages:•No need for fertiliser as the oil (hydrocarbon) does not contain N or P or other nutrients
•No need to wait for growth as algae can be returned to ponds in high concentrations after milking
•No production of dead algal biomass waste stream
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Example processes re-using biomass
•By re-using the catalyst (biomass) bioprocesses can profit by saving time and costs to re-grow the biomass. Examples were:
•Recycle of liquor inoculum of the DiCOM process
•Biofilm reactors = Fixed bed reactors
•Activated sludge system for wastewater treatment
•Algae recycle after removing the endproduct
•Microbial fuel cells
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End of Presentation