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

Example of a renewable biofuel process: DiCOM Take home messages: Combination of aerobic and anaerobic processes is possible (as shwn 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. 3

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 (CH 4, N 2 O) Odour emission 3

Organic Waste Treatment- Composting  Simple aerobic process  Converts putrescible organic waste into humus rich, hygienic product  Problems: Odour caused by raw material exposed to open air Vermin Greenhouse gas emission (CH 4, N 2 O) 4

 An aerobic process  Microbes use oxygen in the air to degrade organic matter  Products: Carbon Dioxide (CO 2 ) + HEAT Composting Overview: 3

Introduction: Organic Waste Treatment - Anaerobic Digestion  An Oxygen Free process  Produces biogas (mixture of CH 4 and CO 2 ) 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, NH 3 ) Thermophilic digestion unstable due to acidification 5

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

 Designed, developed and patented by Organic Resource Technologies Ltd. (Proven process at pilot-scale)  Hybrid process combining aerobic composting with high temperature (thermophilic) anaerobic (no air) digestion  Operated within a single vessel (SBR) minimise in-process handling  Treats Organic Municipal Solid Waste (MSW)  stable compost  renewable energy  19 day processing duration What is the DiCOM ® Process? 7

 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 CO 2 20°C 60°C Phase 1 5 Days Sorted Rubbish The DiCOM ® Process  Organics + O 2  Carbon Dioxide (CO 2 ) Aerobic microbial activity

Air CO 2 Air Biogas  VFA = Volatile Fatty Acids (Acetate, Butyrate, Propionate) Anaerobic Liquid 60°C Heater Phase 1 5 Days Phase 2 7 Days 55°C X Sorted Rubbish The DiCOM ® Process  Fermentation  CO 2 + VFA  VFA  CH 4 & CO 2 (biogas) (methanogens)

Air CO 2 Air Biogas Anaerobic Liquid 60°C Heater Air CO 2 Anaerobic Liquid 35°C Phase 1 5 Days Phase 2 7 Days Phase 3 7 Days 55°C X Compost Sorted Rubbish 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 Start Anaerobic (No Air) Anaerobic (No Air) Direct Transfer Of Anaerobic Liquid Finish Anaerobic (No Air) DiCOM ® Commercial Plant Structure Final Aeration & Empty Final Aeration & Empty Fill & Initial Aeration Anaerobic (No Air) Phase 1 Phase 2 Phase 3 Phase 1 Phase 2 Phase 3 Phase 1 Phase 2 Phase 3

Using 3 identical reactors with rotating phases.  Drain reactor that completed digestion  Transfer 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 the DiCOM process at Murdoch University, Perth.

DiCOM ® Pilot Plant

Western Metropolitan Regional Council (WMRC) Established in 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: 22km 2

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

Reactor Design

 Transfer of active anaerobic culture reduces VFA accumulation (open symbols) Volatile Fatty Acid (VFA) Profile

Electron Balance During aeration … Rubbish O2O2 CO 2  Every O 2 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 CH 4  Every CH 4 contains 8 electrons Methanogen Electron Carbon Hydrogen

Air Exit Gas Air Biogas Anaerobic Liquid 60°C Heater Air Anaerobic Liquid 35°C Phase 1Phase 2Phase 3 55°C X The DiCOM ® Process 20°C Monitor O2O2 O2O2 CH 4 O2O2 O2O2 Exit Gas

Aerobic Anaerobic  50% increase in degradation during the anaerobic phase Electron Equivalents CO 2 CH 4

Reactor Run Time (Days) Molar Electron Flow (mmol/h/kg VS) 16 Electron Flow For Aerobic/Anaerobic Treatments: DiCOM ® Full Composting Full Anaerobic  Low e - flow composting days 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

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

Milking Algae an example of biomass recycle (retention) (the material is supposed to serve as examples that students can use if asked in an exam) 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

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

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