Queensland University of Technology

From the SelectedWorks of Wiji Senadeera PhD

February, 2005

Anaerobic digestion- Institute of SustainableSystems and TechnologiesWijitha Senadeera, University of South Australia

Available at: https://works.bepress.com/wijitha_senadeera/11/

Implementation and Implementation and optimisation optimisation of of

anaerobic digestion to South anaerobic digestion to South

Australian Climatic ConditionsAustralian Climatic Conditions

Wijitha Senadeera

Saiful Bari

Andrew Burge

Institute for Sustainable Systems and Technologies Initiative

Paul Harris

University of Adelaide

Objectives of the projectObjectives of the project

� Characterization and quantification of the

different wastes in the SA region

� Evaluation of Anaerobic Digestion

Technologies available

� Evaluation of economic environmental

benefits associated with anaerobic digestion

� Possible applications of biogas in SA

� Design and construct small scale trial

facility to suit south Australian conditions

What is Anaerobic Digestion ?What is Anaerobic Digestion ?

� A biological process that decomposes organic waste to

produce biogas (CH4 and CO2) and fertilizer under airless

conditions

� Environmentally and economically favourable way to

process organic waste

� A waste management strategy designed to close the loop

for organic waste;

– Generating renewable energy from biogas

– Returning organics back to the soil structure

Polymers substrates(carbohydrates , fats, proteins)

Fragments and soluble polymers

H2 CO2 organic acids acetic acid alcohols

Acetic acids

Methane

1. Hydrolysis Phase

2. Acidogenesis Phase

3. Acetogenesis Phase

4. Methanogenesis Phase

The concept of anaerobic treatment

Parameters in anaerobic digestionParameters in anaerobic digestion

� pH value

� Temperature

� Loading rate

� Retention time (HRT/SRT)

� Toxicity of the trace elements

Anaerobic Digestion

Thermophilic ~ 60°

Mesophilic ~ 35°

80°

40°

10 100Digestion Time (hrs)

Anaerobic Digestion BenefitsAnaerobic Digestion Benefits� Reduce volume of waste going to land fill

� Reduce greenhouse gas emissions

– Methane from landfill

– Carbon dioxide from electricity generation

� Treatment of waste reduces odour, pathogens,

applied in places and times for better nutrient

uptake

� Reduce BOD of waste water

� Manage environmental risks

� Reduction in global warming

Digestion ProcessDigestion Process

BIO GAS

SOLIDS

LIQUOR

FOOD/FARM

WASTES

DIGESTION

Some Industries Identified as Some Industries Identified as

suitable for Anaerobic suitable for Anaerobic

digestion in South Australiadigestion in South Australia

Agricultural waste Agro-industrial waste Municipal waste

Dairy

Farm

Beef cattle

Pig

Chicken

Horse

Sheep

Dairy Processing

Fish processing

Meat processing

Vegetable processing

Wine processing

Olive processing

Breweries

Sewage sludge

Municipal solid waste

Green/botanical waste

Estimated biogas production in Estimated biogas production in

SA based on 2004 statistics of SA based on 2004 statistics of

some waste materialsome waste material

Waste

material

Average biogas

yield per day (m3)

Yearly estimate biogas production in

SA (million m3)

Cattle 0.37 20 (0.07 PJ)

Pig 0.18 30 (0.11 PJ)

Poultry 0.011 15 (0.05 PJ)

Olive waste 3.5 (0.01PJ)

(values given in the brackets are primary energy production calculated based on gas volumes)

Properties of BiogasProperties of Biogas

� 1m3 of biogas

� Generates 1.5 KWh

� Equals 1 lb of LPG

� Equals 0.54 l of Petrol

� Equals 0.52 l of Diesel

� Calorific value ~ 24 MJ/m3

� Contains 65% CH4

& 35% CO2

Source: Horst, W. D. (2000)

Laboratory Testing Facility is Laboratory Testing Facility is

under constructionunder construction

� Determination of biogas yield with respect

to :

– different Total solids and Volatile solids for

different waste types

– At different temperatures

– Composition of biogas

– Mass and energy balance of the conversion

Commonly available AD Commonly available AD

TechnologiesTechnologies

� Standard digester

� Anaerobic contact process

� Anaerobic filter

� Upflow anaerobic sludge blanket

� Hybrid reactors

Standard digesterStandard digester

Anaerobic Digestion

Methane (CH4) Production

Active Mixing

Zone

Fresh sludgeGas Produced

Sludge

Liquid

Lagoon type digesterLagoon type digester

Digester at Adelaide UniversityDigester at Adelaide University

Anaerobic contact processAnaerobic contact process

Anaerobic filterAnaerobic filter

Upflow Upflow anaerobic sludge anaerobic sludge

blanketblanket

Hybrid reactorsHybrid reactors

� Combination of AF and UASB

� Sludge bed at the bottom

� Packing at the top

� High biomass accumulation possible

Possible applicationsPossible applications

� Heating

� Mechanical power

� Electricity generation

� Co-generation (CHP)

Micro turbine

Evaluation of environmental Evaluation of environmental

benefitsbenefits

� Emission benefits

� Land use

� Reduction in green house gas potential

Research at UNISA (ISST)Research at UNISA (ISST)� A detailed evaluation and quantification of wastes

in South Australian region suitable for anaerobic digestion

� Design and construction of a suitable small scale facility for testing different wastes and treatment methods

� Detailed evaluation and quantification of environmental benefits

� Flow diagrams and preliminary facilities depicting the conceptual layout of possible pilot plants

AcknowledgementsAcknowledgements

� Director/Agricultural Machinery Research and

Design Centre for providing me a place to stay

and carryout this study

� Directors/Institute for Sustainable Systems and

Technologies Initiative, for provision of the grant

� Director/Sustainable Energy Centre for making

me enthusiastic on this Bio-energy area

THANK YOUTHANK YOU