The Design & Build of a Biodigester Toilet

The Design & Build of a Biodigester ToiletDesign Project 1587

James Bass, Nishanth Cheruvu, Natasha Rayan, Charlie Savory, Kieren Sheehan

The Design & Build of a Biodigester Toilet

University of Adelaide Natasha Rayan 2

• Problem Background• Significance• Scope• Technical Background• Design• Testing & Operation• Current Progress• Future Work• Design Improvements

Natasha Rayan

Nishanth Cheruvu

Charlie Savory

James Bass

Kieren Sheehan

Problem Background

• 2.6 billion people lack access to facilities (WHO 2014)

• 2 million deaths per year (WHO 2014) • Some health implications– Cholera– Diarrhoea– Fluorosis– Hepatitis A– Schistosomiasis– Typhoid

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Sanitation

University of Adelaide Natasha Rayan

Problem Background

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(SSMV 2007)

(The Safe Toilet Blog 2010)

Definitions of Sanitation


Problem Background

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Definitions of Sanitation

Shared Sanitation:

“sanitation facility that hygienically separates human excreta from human contact and is shared between two or more households, including public toilets.”

(WHO 2014)


Problem Background

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The Proportion of the population using improved sanitation (WHO 2010)

Access to Sanitation


Problem Background

• Over 3 billion people rely on burning solid fuels (WHO 2014)

• 4 million deaths per year (GACC 2010) • Solid Fuels

– Coal– Wood– Wheat– Straw– Manure

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Energy Usage & Indoor Air Pollution


Problem Background

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(UCR Today 2012)

Social Implications


Problem Background

• Modern Fuels– Ethanol– LPG– Kerosene– Biogas

• Fewer harmful emissions• More efficient• Higher temperatures

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Alternative Energy


Problem Background

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Indication of household solid fuel use globally (GACC 2007)

Solid Fuel Usage


Problem Background

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The Proportion of the population using improved sanitation (WHO 2010)

Access to Sanitation


Problem Background

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Biomass Usage


Scope

• Design and build a WHO defined “shared sanitation” facility for waste collection

• Employ anaerobic digestion as a waste management strategy

• Ensure portability

• Comply with relevant Australian Standards

• Demonstrate a viable use for the biogas

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Objectives


Technical Background

• Human waste is harmful• Pathogens

– Viruses, bacteria and parasites spread disease

• Requires treatment

University of Adelaide Charlie Savory 14

Waste Management

• Aerobic: The breakdown of organic matter in the presence of oxygen– Major product CO2

• Anaerobic: The breakdown of organic matter in the absence of oxygen– Major product biogas (CH4 and CO2)

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DigestionTechnical Background

University of Adelaide Charlie Savory


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(Amon et al. 2005)

Biogas

Technical Factors- Temperature- Retention Time- Volatile Solids %- C/N Ratio

Gas Component

Concentration Range

Mean Value

Methane 45-75% 60%

Carbon Dioxide 25-53% 35%

Water Vapour 0-10% 3%

Nitrogen 0.01-5% 1%

Oxygen 0.01-2% 0.3%

Hydrogen 0-1% <1%

Ammonia 0.01-2.5mg/m3 0.7%



• Thermophilic: 49°C – 57°C– 10 day retention time– More common in developed industrial countries

• Mesophilic: 30°C – 38°C– 30-40 day retention time– More applicable to developing countries

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Temperature & Retention Time



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Biomass Usage



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(Salam et al. 2005)

Biogas Output

Feedstock Biogas Yield (L/kg)

Daily Production

(kg/day)

Daily Biogas Production

(L/day)

Human 30 0.6 18

Cow 25 12 300

Chicken 100 0.1 10

Pig 25 2 50



• Biodigester– Sealed container in which anaerobic digestion process

takes place

• Existing designs– Fixed dome– Floating drum– Plug flow

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Existing Designs



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(SNV 2009) (Energypedia 2009)

Fixed Dome Biodigester



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(SNV 2009) (Energypedia 2009)

Floating Drum Biodigester



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(SNV 2009) (Maximiliano Ortega 2008)

Plug-Flow Biodigester



• Prefabricated, portable biodigesters versus brick/concrete based biodigesters

(Cardo 2013) (Solar Cities 2010)

Emerging Designs

23University of Adelaide Charlie Savory


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(Coffee et al. 2009)

• Design fits the scope of 2014 project

• Several issues with design and testing

Combined Systems


Design

Isolate human waste from the user of the toiletUse the waste collected to produce biogasAffordable for low income communitiesSimple to assemble and disassembleEntirely portableSimple to use and maintain by the end users

University of Adelaide Nishanth Cheruvu 26

Criteria

Design

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Conceptual

• 4 conceptual designs• Differed in several

important ways– Digestion stages– Biodigester mechanism

• Shared common aspects– Simplicity– Effectiveness

Concept Design 1

University of Adelaide Nishanth Cheruvu

Design

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Common Aspects

Crushed BricksOutletGas Collection


Concept Design 1

Design

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Preliminary Design


Design

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Preliminary Design


Design

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Preliminary Design


Toilet Location

Design

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Preliminary Design


Design

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Preliminary Design


Inflatable Membrane

Design

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Detailed Design


Design

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Digestion Tanks• 1000L polyethylene tanks• Lightweight• Easy to modify

Detailed Design


Design

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Detailed Design

Piping• 100mm PVC for waste inlet• 20mm Blue-Line Poly for gas flows• 50mm Suction Pipe for tank connections


Design

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Detailed Design

Bioballs• Form a biofilm• Avoid clogging of effluent at the outlet


(Drsfostersmith 2014)

Design

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Costing

Subsystem Final Cost

Biodigester Tanks (x2) $400

Gas Membrane (x1) $196

Parts and Fittings $282

Toilet $0

Entire System $878


Testing & Operation

University of Adelaide James Bass 39

.

Location

• Needed– Easy access to feedstock– Security– Willing land owner

• Urrbrae High School– Farm abundant with animal waste– Locked greenhouses and gates– Active biogas program

Testing & Operation

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Sourcing Feedstock

•Human waste difficult to source•Pig waste

• Easy access•Known biogas producer

University of Adelaide James Bass

Testing & Operation

• Fire and Explosion– Flame traps designed– Explosive zoning (AS 60079.10)– Warning signs

• Exposure to Pathogens– PPE use mandatory– Standard operating procedure

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Major Risks


Testing & Operation

• Urrbrae Greenhouse– Removed the need for insulation– Provided extra security

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Thermal conditions


Testing & Operation

• Tested for leaks before addition of feedstock• During construction, digestion process was

started in four 76L drums– Added to system once construction and safety testing

was completed

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System Start-up


Testing & Operation

• Continuous process to replicate shared toilet use• 245L total feedstock added twice per week

– Equivalent to 2.75L solid and 67L liquid added daily

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Operating Procedure


Testing & Operation

• Greenhouse temperature• Feedstock pH

– Indicative of system health

• Feedstock temperature• Gas composition• Flame test• Biogas volume

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Process & Data


Current Progress

University of Adelaide Kieren Sheehan 46

Construction

• Constructed entirely by project team• Issues with gas leaks• Two weeks to complete

Current Progress

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Prototype

• Completed and filled 11th September

• No toilet– To be installed

University of Adelaide Kieren Sheehan

Current Progress

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Preliminary Results

• No flammable gas produced• Biogas production expected in 2 weeks• Tested for CH4 & CO2


Future Work

• Provided by Caroma• Construct wooden support

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Toilet


Future Work

• If successful – Urrbrae will continue to run digester

• Otherwise– Digested waste disposed appropriately– Parts recycled

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Post Treatment


Design Improvements

• Greenhouse provides warm environment• Include insulation

– Add insulating material– Tanks underground

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Improved Insulation


Design Improvements

• Inflatable membrane– Cheap– Effective– Portable– Easily damaged

• Floating drum– Provides constant gas

pressure

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Improved Gas Collection System


Design Improvements

• Cooker• Heater• Lamp• Generator

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Practical Application of Biogas


Design Improvements

• Privacy• Access to toilet• Support user and toilet

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Toilet Housing


Design Improvements

• Layer of scum forms on surface• Breaks up scum layer• Accelerates gas production

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Stirrer


Summary

• Poor sanitation kills 2 million annually (WHO 2014)

• Solid fuel use kills 4 million annually (GACC 2010)• Biodigester toilet may address both issues

• Saving 6 million lives every year• Designed and testing prototype system

56University of Adelaide Kieren Sheehan

Thanks

• Dr Cristian Birzer• Dr Paul Medwell• Neil Harris & Urrbrae Agricultural High School• Mike Hatch• Paul Stewart & Mitre 10 Malvern• Caroma• Lynair Logistics

57University of Adelaide Kieren Sheehan

References• Amon, T., Amon, B., Kryvoruchko, V., Zollitsch, W., Mayer, K. and Gruber, L. (2007). Biogas production from maize

and dairy cattle manure—influence of biomass composition on the methane yield. Agriculture, Ecosystems \& Environment, 118(1), pp.173--182.

• Cleancookstoves.org, (2010). Data & Statistics. [online] Available at: http://www.cleancookstoves.org/resources/data-and-statistics/ [Accessed 23 Sep. 2014].

• Culhane, T. (2014). SOLAR CITIES. [online] Solarcities.blogspot.com.au. Available at: http://solarcities.blogspot.com.au/ [Accessed 16 Sep. 2014].

• Drsfostersmith.com, (2014). [online] Available at: http://www.drsfostersmith.com/images/Categoryimages/larger/lg_26378_35703D.jpg [Accessed 18 Sep. 2014].

• Hymans, G. (2013). China Non-Stop: Good manners in China: what could change?. [online] Chinanon-stop.com. Available at: http://www.chinanon-stop.com/2013/07/good-manners-in-china-what-could-change.html [Accessed 16 Sep. 2014].

• Junfeng, L., Runqing, H., Yanqin, S., Jingli, S., Bhattacharya, S. and Abdul Salam, P. (2005). Assessment of sustainable energy potential of non-plantation biomass resources in China. Biomass and Bioenergy, 29(3), pp.167--177.

• Junfeng, L., Runqing, H., Yanqin, S., Jingli, S., Bhattacharya, S. and Abdul Salam, P. (2005). Assessment of sustainable energy potential of non-plantation biomass resources in China. Biomass and Bioenergy, 29(3), pp.167--177.

• Ortega, M., Agriculture, I. and Society, F. (2009). Installation of a low cost polyethylene biodigester.• Snvworld.org, (2009). Biogas. [online] Available at: http://www.snvworld.org/en/biogas [Accessed 23 Sep. 2014].• Sswm.info, (2014). Overhung Latrine | SSWM. [online] Available at: http://www.sswm.

info/category/implementation-tools/wastewater-treatment/hardware/user-interface/overhung-latrine [Accessed 16 Sep. 2014].

• Teune, B. (n.d.). Sector Development for Domestic Biodigesters: Experiences of SNV, Dutch Development Organisation. p.125.

• UCR Today, (2012). Woman & Child Cooking. [image] Available at: http://ucrtoday.ucr.edu/6664 [Accessed 10 Sep. 2014].

• Who.int, (2014). WHO | Household air pollution and health. [online] Available at: http://www.who.int/mediacentre/factsheets/fs292/en/ [Accessed 23 Sep. 2014].

• World Health Organisation, (2014). Progress on drinking water and sanitation Joint Monitoring Programme update 2014. Geneva: WHO, pp.3-4.

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Engineering

The Design & Build of a Biodigester Toilet