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

3

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

3

• 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)

4

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

5

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

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18

Reactor Run Time (days)

Tem

pe

ratu

re (

°C)

0

10

20

30

40

50

60

70

80

OU

R (m

mo

l/h/k

g V

S)

Temperature OUR

An aerobic process

Microbes use oxygen in the air to degrade organic matter

Products: Carbon Dioxide (CO2) + HEAT

Composting Overview:

3

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)

6

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

0102030405060708090

100

5 7 9 11Reactor Run Time (days)

Co

nce

ntr

atio

n (

mM

)

0

1

2

3

4

5

6

7

8

9

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?

0

50

100

150

200

250

0 2 4 6 8 10 12 14 16 18Reactor Run Time (days)

Ele

ctro

n E

quiv

ale

nts

(m

mo

l/kg/

h)

Optimised

0

50

100

150

200

250

0 2 4 6 8 10 12 14 16 18

Reactor Run Time (days)

Ele

ctr

on

Eq

uiv

ale

nts

(m

mo

l/k

g/h

)

Aerobic Anaerobic Aerobic 2 Anaerobic 2 Series3 Series4

Aerobic AerobicAnaerobic

50% increase in degradation during the anaerobic phase

Electron Equivalents

CO2 CH4

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14 16 18 20

Reactor Run Time (Days)

Mo

lar

Ele

ctro

n F

low

(mm

ol/h

/kg

VS

)

16

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

3

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.

3

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

3

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

3

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

3

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

3

End of Presentation