• Daniel Ikhu-Omoregbe; Seun Oyekola

• HOD; Senior Lecturer

• Cape Peninsula University of Technology

• South Africa

POTENTIAL OF BIOGAS AS A

RENEWABLE AND

SUSTAINABLE ENERGY

SOURCE

INTRODUCTION & BACKGROUND

• World is currently challenged with energy crisis and the

associated global warming

• Renewable energy sources e.g. solar and wind are

attractive

• Sustainable energy sources and waste management

approaches have potential to curb crisis

• Biogas from wastes can be used for replacement or

supplement of fossil fuels

What is Biogas • Produced by the breakdown of organic matter in the

absence of oxygen

• Raw materials: sugarcane residue, maize silage, manure,

sewage , municipal waste etc.

• Chemical composition: methane (CH4) [~50%], carbon

dioxide (CO2) [~25%], hydrogen sulphide (H2S), moisture

[~1%] & nitrogen (N2) [~10%]

What is Biogas (cont’d) • Uses: heating & electricity generation

• Can be cleaned & upgraded to natural gas standards

(biogas to biomethane).

• Energy composition: 18630-26081 kJ/m3 depending on

CH4 content

Landfill gas to energy (LFGTE)

• Landfill: One of the most commonly adopted technologies

for municipal solid waste (MSW) disposal.

• Landfill gas (LFG): type of biogas produced from landfills.

• LFG is composed of 41% of methane

Anaerobic Digestion

A biological process in which microorganisms break

down biodegradable material in the absence of oxygen,

producing CO2, CH4 etc

Waste Feedstocks

• A wide variety: wastes from households, food & biomass, processing industry, MBT (mechanical biological treatment) & agricultural facilities.

• Anaerobic digesters considerations: contaminants and other environmental/ physicochemical factors. Owing to feedstock complexity, pre-treatment required

Why Biogas as renewable energy resource

• Most waste management approaches are for pollution

prevention & public health protection.

• Integrated approach to the management of wastes

which focuses on energy recovery will have a

significant economic and environmental impact.

– Cogeneration of “green” electricity: CHP systems driven by

biogas used for heating digesters, premises (households,

businesses). Electricity used locally or transmitted to public

electricity grid

– Reduction of dependence on fossil fuels

– Reduction of GHG emissions

– Reduction of wastes

– Reduction of soil & groundwater pollution

– Contribution to national targets (environmental & energy)

BENEFITS TO SOCIETY cont’d

– Compatibility with water scarcity

– Job creation

– Convenient storage

– Flexible & efficient end use of biogas: CHP, cooking, lighting,

combustion, fuels for vehicles etc

– Reduction of GHG emissions

– Reduction of wastes

– Reduction of soil & groundwater pollution

– Contribution to national targets (environmental & energy)

POTENTIAL IN SA: SMALL SCALE

APPLICATION • Simple, low cost, low maintenance technology

• Biogas systems were first introduced to South Africa in 1957 by a pig farmer in Johannesburg.

• 200 biogas digesters scattered across South Africa. Mostly small domestic units and a few NGO driven initiatives.

• 1.0 m3/day biogas

– Sufficient to power a two-plate gas stove for a couple of hours

– Production requires

• black water from 15 to 20 people or manure from three cattle, or 10 pigs, or 1,000 chickens.

• A biogas digester for a smallholding costs ~R40,000.

POTENTIAL IN SA: LARGE SCALE

APPLICATION

• Large scale designed to process large amounts of feedstock.

• Decentralised farm-size units are increasing productivity by

supplementing their feedstock with agricultural residues

• BiogasSA has undertaken a 500 kW project for an abattoir with

potential of generation of ~60% electricity requirement from biogas (an

estimated 1.4 GWh/year).

– Feedstock is slaughter waste. Hence an integrated approach for waste

disposal & energy production

R&D+ Capacity building Dept. of Chemical Engineering

1. Landfill gas to energy (LFGTE) Project: LG from MSW can be captured, cleaned & converted into useable energy or electricity to address SA energy demands.

• CCT potential – Population of 3.7 million. Manages 5000 wastes/d

– 3 operating landfill sites. Bellville site linked to CPUT project

– Bellville site received received 434 051 tonnes of MSW in 2013

– Potential for 36 463 m3 of biogas≅ 2 104 023 MWh electricity≅ R141 million = R35.25 million at 25% recovery

2. Biogas from sewage with production of biosolids: process mediated by Acti-zyme. – Based in Chitungwiza, Harare, Zimbabwe

– Waste from WWTP poorly handled

– Bioenergy & biosolids obtainable

– Bioenergy for energy needs of plants & biosolids as fertilizer

CONCLUSION

• Biogas industry..

1. Has the potential to displace up to 2 500 MW of grid

electricity in SA (ESI Africa, 2013).

2. Could complement the govt.’s Independent Power

Programme (IPP) aimed at producing 3 725 MW of

power from renewable sources by 2016.

3. Has potential to develop a domestic industry in

excess of R10 billion