Abstract
This ȱ paper ȱ profiles ȱ biomass ȱ as ȱ a ȱ source ȱ of ȱ sustainable ȱ energy.
ȱȱ It ȱ illustrates ȱ the ȱ scale ȱ and ȱ scope ȱ of ȱ bioenergy ȱ world ȱ wide ȱ and ȱ the ȱ range ȱ of ȱ biomass ȱ resources ȱ that ȱ can ȱ be ȱ converted ȱ to ȱ heat, ȱ power, ȱ fuels ȱ and ȱ other ȱ value Ȭ added ȱ products.
ȱ It ȱ notes ȱ the ȱ emergence ȱ of ȱ wood ȱ pellets ȱ as ȱ a ȱ renewable ȱ fuel.
ȱ ȱ The ȱ paper ȱ takes ȱ a ȱ look ȱ at ȱ greenhouse ȱ gas ȱ emissions ȱ of ȱ bioenergy ȱ systems ȱ and ȱ compares ȱ these ȱ to ȱ several ȱ other ȱ energy ȱ sources.
ȱȱ Energy ȱ conversion ȱ processes ȱ and ȱȱ technologies ȱ are ȱ examined ȱ and ȱ illustrated ȱ by ȱ examples ȱ of ȱ wood ȱ fuelled ȱ bioenergy ȱ plants.
ȱȱ Emerging ȱ technologies ȱ examined ȱ are ȱ biomass ȱ gasification ȱ and ȱ the ȱ production ȱ and ȱ use ȱ of ȱȱ pyrolysis ȱ bio Ȭ oil.
ȱ ȱ Bioenergy ȱ can ȱ provide ȱ several ȱ co Ȭ values ȱ and ȱ co Ȭ products ȱ and ȱ these ȱ are ȱ briefly ȱ covered, ȱ together ȱ with ȱ the ȱ various ȱ environmental ȱ and ȱ social ȱ values ȱ bioenergy ȱ can ȱ provide.
ȱȱ The ȱ paper ȱ concludes ȱ by ȱ providing ȱ a ȱ brief ȱ summary ȱ of ȱ the ȱ Australian ȱ bioenergy ȱ industry.
ȱ
Introduction
Biomass ȱ refers ȱ to ȱ organic ȱ matter, ȱ derived ȱ in ȱ recent ȱ times, ȱ directly ȱ or ȱ indirectly, ȱ from ȱ plants, ȱ as ȱ a ȱ result ȱ of ȱ photosynthesis.
ȱ ȱ It ȱ includes ȱ a ȱ wide ȱ variety ȱ of ȱ materials, ȱ from ȱ forestry ȱ and ȱ agricultural ȱ residues, ȱ to ȱ organic ȱ waste ȱ by Ȭ products ȱ from ȱ various ȱ industries, ȱ purpose ȱ grown ȱ energy ȱ crops, ȱ to ȱ woody ȱ weeds ȱ and ȱ municipal ȱ green ȱ waste.
ȱȱ
Bioenergy ȱ is ȱ the ȱ term ȱ used ȱ to ȱ describe ȱ energy ȱ and ȱ energy ȱ related ȱ products ȱ derived ȱ from ȱ ȱ biomass.
ȱ
Bioenergy ȱ can ȱ be ȱ regarded ȱ as ȱ a ȱ form ȱ of ȱ solar ȱ energy, ȱ as ȱ photosynthesis ȱ combines ȱ atmospheric ȱ carbon ȱ dioxide ȱ with ȱ water ȱ in ȱ the ȱ presence ȱ of ȱ sunlight ȱ to ȱ form ȱ the ȱ biomass, ȱ while ȱ also ȱ producing ȱ oxygen.
ȱ ȱ This ȱ process ȱ ȱ ȱ can ȱ be ȱ represented ȱ by ȱ the ȱ formula: ȱ
Light
CO
2 ȱȱ + ȱȱ 2H
2
O ȱ ([CH
2
O] ȱ + ȱ H
2
O) ȱ + ȱ O
2 ȱ
Heat ȱ ȱ where ȱ [CH
2
O] ȱ represents ȱ the ȱ biomass ȱ (as ȱ ȱ carbohydrates).
ȱ
The ȱ energy ȱ bound ȱ into ȱ the ȱ biomass ȱ can ȱ be ȱ recovered ȱ through ȱ a ȱ variety ȱ of ȱ bioenergy ȱ processes ȱ and ȱ technologies.
ȱ ȱ During ȱ the ȱ energy ȱ recovery ȱ process, ȱ the ȱ carbon ȱ dioxide ȱ bound ȱ in ȱ the ȱ biomass ȱ is ȱ released ȱ to ȱ the ȱ
Australian Forest Growers Conference 2006 ȱ ȱ atmosphere.
renewable, ȱ ȱ ȱ Bioenergy when ȱ the illustrated ȱ in ȱ Figure ȱ 1.
ȱ ȱ ȱ is ȱ regarded biomass ȱ ȱ energy ȱ consumption ȱ of ȱ around ȱ 400EJ/year.
ȱ as resource consumed ȱ in ȱ the ȱ energy ȱ conversion ȱ process ȱ is ȱ replenished ȱ by ȱ the ȱ growth ȱ of ȱ an ȱ equivalent ȱ amount ȱ of ȱ biomass.
ȱ ȱ Globally ȱ some ȱ 220 ȱ billion ȱ dry ȱ tonnes ȱ of ȱ biomass ȱ are ȱ produced ȱ through ȱ photosynthesis ȱ per ȱ year.
ȱȱ The ȱ energy ȱ stored ȱ globally ȱ in ȱ biomass ȱ represents ȱ about ȱ
0.02% ȱ of ȱ solar ȱ energy ȱ incident ȱ on ȱ earth.
ȱȱ This ȱ small ȱ portion ȱ of ȱ the ȱ energy ȱ absorbed ȱ by ȱ biomass ȱ is ȱ equivalent ȱ to ȱ approximately ȱ eight ȱ times ȱ the ȱ global ȱ anthropogenic ȱ primary ȱ
Biomass ȱ can ȱ present ȱ itself ȱ in ȱ many ȱ forms, ȱ from ȱ relatively ȱ dry ȱ (e.g.
ȱ rice ȱ husks) ȱ to ȱ very ȱ desired ȱ end ȱ products.
ȱ ȱ Converting ȱ the ȱ biomass ȱ can ȱ utilise ȱ a ȱ variety ȱ of ȱ paths ȱ and ȱ technologies.
ȱ ȱ The ȱ primary ȱ conversion ȱ processes ȱ are ȱ via ȱ thermal, ȱ biochemical ȱ or ȱ mechanical/physical ȱ processing.
ȱ ȱ These ȱ are ȱ
Bioenergy ȱ has ȱ an ȱ inherent ȱ advantage ȱ over ȱ other ȱ forms ȱ of ȱ renewable ȱ energy ȱ such ȱ as ȱ wind ȱ and ȱ solar ȱ energy.
ȱȱ As ȱ the ȱ energy ȱ bound ȱ into ȱ the ȱ biomass ȱ provides ȱ inherent ȱ energy ȱ storage, ȱ bioelectricity ȱ can ȱ be ȱ dispatched, ȱ providing ȱ firm ȱ capacity, ȱ unlike ȱ some ȱ other ȱ
332 ȱ ȱ wet ȱ (sewage ȱ can ȱ contain ȱ 98 ȱ percent ȱ water).
ȱȱ
As ȱ such, ȱ appropriate ȱ technologies ȱ are ȱ required ȱ to ȱ convert ȱ the ȱ biomass ȱ to ȱ the ȱ

sources ȱ dispatched ȱ by ȱ nature.
ȱ ȱ This ȱ allows ȱ excellent ȱ utilisation ȱ of ȱ the ȱ bioenergy ȱ plant’s ȱ capacity.
ȱ ȱ ȱ
Biomass
Wood, MSW, Energy Crops... Manures, Sewage, Food Wastes ... Oil Palm ...
Thermal Processing Biochemical Mechanical
Combustion Gasification Pyrolysis
Anaerobic
Digestion
Fermentation
Crushing
Oil Crops
Heat and Power
Chemical
Feedstocks
Figure 1: Bioenergy conversion routes. ȱ
Scale of bioenergy
At ȱ a ȱ global ȱ level, ȱ in ȱ 2004, ȱ renewables ȱ accounted ȱ for ȱ 13.3% ȱ of ȱ the ȱ 10,579 ȱ Mtoe ȱ
(million ȱ tonnes ȱ oil ȱ equivalent) ȱ of ȱ the ȱ world’s ȱ primary ȱ energy ȱ supply ȱ (International ȱ Energy ȱ
Agency ȱ 2005).
ȱȱ This ȱ is ȱ equivalent ȱ to ȱ 443 ȱ EJ ȱ of ȱ primary ȱ energy ȱ supply.
ȱ ȱ Biomass ȱ and ȱ waste ȱ
(97% ȱ of ȱ which ȱ is ȱ biomass) ȱ represented ȱ almost ȱ
80% ȱ of ȱ the ȱ total ȱ renewables, ȱ followed ȱ by ȱ hydro ȱ at ȱ 16.5% ȱ of ȱ the ȱ renewables ȱ component.
ȱȱ
Biomass ȱ as ȱ a ȱ primary ȱ energy ȱ source ȱ is ȱ of ȱ the ȱ same ȱ order ȱ of ȱ magnitude ȱ as ȱ natural ȱ gas, ȱ coal ȱ and ȱ oil ȱ and ȱ is ȱ more ȱ than ȱ double ȱ nuclear ȱ ȱ energy.
ȱȱȱ
When ȱ one ȱ considers ȱ only ȱ electricity, ȱ renewable ȱ electricity ȱ is ȱ the ȱ third ȱ largest ȱ contributor ȱ at ȱ the ȱ global ȱ level, ȱ after ȱ coal ȱ and ȱ gas ȱ and ȱ ahead ȱ of ȱ nuclear ȱ and ȱ oil.
ȱ ȱ ȱ In ȱ 2004 ȱ renewables ȱ accounted ȱ for ȱ 17.6% ȱ of ȱ the ȱ total ȱ global ȱ electricity ȱ production.
ȱ ȱ 90% ȱ of ȱ the ȱ renewable ȱ electricity ȱ was ȱ produced ȱ by ȱ hydro ȱ power ȱ plants, ȱ followed ȱ by ȱ biomass ȱ and ȱ waste ȱ
Ethanol Biodiesel at ȱ 6% ȱ of ȱ the ȱ renewable ȱ electricity ȱ component.
ȱȱ
Although ȱ fast ȱ growing, ȱ geothermal, ȱ solar ȱ and ȱ wind ȱ accounted ȱ for ȱ less ȱ than ȱ 4% ȱ of ȱ renewable ȱ electricity ȱ in ȱ 2004.
ȱ ȱ In ȱ 2004 ȱ it ȱ was ȱ estimated ȱ that ȱ installed ȱ biomass ȱ electricity ȱ generating ȱ capacity ȱ in ȱ OECD ȱ countries ȱ totalled ȱ approximately ȱ 25,000 ȱ MW.
ȱ ȱ Of ȱ this ȱ
13.6
ȱ GW ȱ was ȱ solid ȱ biomass, ȱ 6.8
ȱ GW ȱ municipal ȱ solid ȱ waste, ȱ 2.6
ȱ GW ȱ gas ȱ from ȱ biomass ȱ and ȱ 2.7
ȱ GW ȱ of ȱ capacity ȱ was ȱ non Ȭ specified ȱ combustible ȱ renewables ȱ and ȱ wastes.
ȱȱȱ ȱ
As ȱ such ȱ bioenergy ȱ is ȱ an ȱ important ȱ contributor ȱ to ȱ world ȱ energy ȱ supplies.
ȱ ȱ In ȱ
Australia, ȱ biomass ȱ contributes ȱ approximately ȱ one ȱ percent ȱ of ȱ the ȱ bioelectricity ȱ energy ȱ mix, ȱ with ȱ sugar ȱ cane ȱ bagasse ȱ dominating ȱ at ȱ 368 ȱ ȱ
MW ȱ installed ȱ capacity.
ȱ ȱ Landfill ȱ gas ȱ contributes ȱ approximately ȱ 105 ȱ MW, ȱ with ȱ other ȱ major ȱ contributions ȱ from ȱ sewage ȱ gas ȱ and ȱ black ȱ liquor ȱ (BCSE ȱ 2004).
ȱȱȱ
Australian Forest Growers Conference 2006 333

Greenhouse gas emissions
As ȱ noted ȱ above, ȱ bioenergy ȱ is ȱ essentially ȱ carbon ȱ dioxide ȱ neutral.
ȱ ȱ This ȱ is ȱ recognised ȱ under ȱ the ȱ Kyoto ȱ Protocol.
ȱ ȱ However, ȱ even ȱ when ȱ one ȱ takes ȱ into ȱ account ȱ the ȱ fossil ȱ fuels ȱ used ȱ in ȱ the ȱ production, ȱ harvesting, ȱ transportation ȱ and ȱ fuel ȱ processing ȱ of ȱ the ȱ biomass, ȱ the ȱ net ȱ carbon ȱ dioxide ȱ emissions ȱ associated ȱ with ȱ a ȱ bioenergy ȱ plant ȱ are ȱ generally ȱ very ȱ small ȱ and ȱ only ȱ approximately ȱ five ȱ percent ȱ of ȱ that ȱ of ȱ a ȱ coal ȱ fired ȱ power.
ȱȱ
This ȱ is ȱ illustrated ȱ in ȱ Table ȱ 1 ȱ which ȱ compares ȱ the ȱ life ȱ cycle ȱ emissions ȱ of ȱ carbon ȱ dioxide ȱ
(equivalent) ȱ emissions ȱ of ȱ several ȱ fossil ȱ fuel ȱ and ȱ renewable ȱ energy ȱ sources.
ȱ ȱ
Table 1: Life cycle carbon dioxide emissions for various technologies (g/kWh).
Technology g/kWh
CO
2
Coal: Best Practice
Natural gas: in combined cycle plant
Onshore wind
Hydro - existing large
Hydro – small-scale
Decentralised photovoltaic (PV)- retrofit
Decentralised PV – new houses
Bioenergy – poultry litter - gasification
Bioenergy – poultry litter – steam cycle
Bioenergy – straw – steam cycle
Bioenergy – straw - pyrolysis ȱ
Bioenergy – energy crops - gasification
Bioenergy – forestry residues – steam cycle
Bioenergy – forestry residues - gasification
Bioenergy – animal slurry – anaerobic digestion
Landfill gas
Sewage gas
14
29
24
31
49
4
Source: DTI 1999.
5
160
178
8
10
13
11
955
446
9
32
Bioenergy technologies
Bioenergy ȱ is ȱ well ȱ established, ȱ with ȱ some ȱ 90 ȱ percent ȱ of ȱ modern ȱ bioenergy ȱ plants ȱ using ȱ combustion ȱ for ȱ providing ȱ heat ȱ and ȱ power.
ȱȱ
Australian Forest Growers Conference 2006
The ȱ quest ȱ for ȱ greater ȱ energy ȱ conversion ȱ efficiency ȱ has ȱ led ȱ to ȱ the ȱ development ȱ of ȱ gasification ȱ and ȱ pyrolysis ȱ bio Ȭ oil ȱ technologies, ȱ which ȱ allows ȱ the ȱ adoption ȱ of ȱ combustion ȱ turbine ȱ technologies ȱ and ȱ opens ȱ the ȱ way ȱ to ȱ combined ȱ cycle ȱ operation ȱ (where ȱ the ȱ hot ȱ exhaust ȱ gases ȱ from ȱ the ȱ combustion ȱ turbine ȱ are ȱ used ȱ to ȱ raise ȱ steam, ȱ which ȱ drives ȱ a ȱ steam ȱ turbine ȱ and ȱ produces ȱ additional ȱ electricity ȱ from ȱ the ȱ same ȱ fuel ȱ source).
ȱ ȱ ȱ The ȱ major ȱ bioenergy ȱ technologies ȱ are ȱ summarised ȱ below.
ȱ
Combustion and co-firing
Two ȱ main ȱ technologies ȱ dominate ȱ biomass ȱ combustion, ȱ grate ȱ combustors ȱ and ȱ fluidised ȱ bed ȱ combustors.
ȱ ȱ Each ȱ of ȱ these ȱ main ȱ technologies ȱ has ȱ variants, ȱ customised ȱ for ȱ the ȱ specific ȱ fuel ȱ and ȱ project ȱ conditions.
ȱ ȱ Grate ȱ type ȱ combustors ȱ may ȱ be ȱ travelling ȱ grates, ȱ vibrating ȱ grates, ȱ or ȱ ȱ pin Ȭ hole ȱ grates.
ȱ ȱ Fuel ȱ is ȱ generally ȱ introduced ȱ into ȱ the ȱ combustor ȱ via ȱ an ȱ auger ȱ or ȱ a ȱ spreader Ȭ stoker.
ȱȱ The ȱ fuel ȱ then ȱ moves ȱ across ȱ the ȱ grate, ȱ drying, ȱ devolatising, ȱ burning, ȱ with ȱ the ȱ residual ȱ ash ȱ being ȱ removed ȱ via ȱ a ȱ variety ȱ of ȱ methods.
ȱȱ The ȱ fly ȱ ash ȱ is ȱ often ȱ used ȱ as ȱ a ȱ soil ȱ amendment, ȱ while ȱ bottom ȱ ash ȱ can ȱ be ȱ used ȱ as ȱ road ȱ base.
ȱ ȱ Biomass ȱ ash ȱ is ȱ often ȱ free ȱ of ȱ toxic ȱ metals ȱ associated ȱ with ȱ coal ȱ ash ȱ and ȱ the ȱ volumes ȱ are ȱ generally ȱ much ȱ less.
ȱȱ
A ȱ grate ȱ combustor ȱ is ȱ ȱ used ȱ in ȱ the ȱ Rocky ȱ
Point, ȱ Queensland ȱ 30 ȱ MW ȱ cogeneration ȱ plant ȱ which ȱ for ȱ part ȱ of ȱ the ȱ year ȱ is ȱ fuelled ȱ on ȱ wood ȱ waste.
ȱ ȱ
In ȱ fluidised ȱ beds, ȱ the ȱ biomass ȱ is ȱ introduced ȱ into ȱ a ȱ hot, ȱ inert ȱ bed, ȱ (such ȱ as ȱ sand), ȱ where ȱ small ȱ quantities ȱ of ȱ biomass ȱ (generally ȱ a ȱ few ȱ percent ȱ of ȱ the ȱ bed ȱ mass) ȱ are ȱ combusted.
ȱȱ
Fluidised ȱ beds ȱ operate ȱ at ȱ approximately ȱ
850°C, ȱ which ȱ results ȱ in ȱ low ȱ NOx ȱ formation.
ȱȱ
Sulfur ȱ emissions ȱ can ȱ also ȱ be ȱ limited, ȱ if ȱ necessary, ȱ by ȱ adding ȱ limestone ȱ or ȱ dolomite ȱ to ȱ the ȱ bed.
ȱ ȱ A ȱ variant ȱ of ȱ ȱ the ȱ bubbling ȱ fluidised ȱ bed ȱ combustor ȱ (FBC) ȱ is ȱ the ȱ circulating ȱ FBC.
ȱ ȱ A ȱ prime ȱ example ȱ of ȱ the ȱ circulating ȱ FBC ȱ technology ȱ may ȱ be ȱ found ȱ at ȱ
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the ȱ Alholmens ȱ Kraft ȱ pulp ȱ and ȱ paper ȱ mill ȱ in ȱ
Finland, ȱ where ȱ the ȱ world’s ȱ largest ȱ biomass ȱ boiler ȱ has ȱ a ȱ capacity ȱ of ȱ 550 ȱ MW th ȱ and ȱ 240 ȱ ȱ
MW e
.
ȱ
A ȱ third ȱ variant ȱ of ȱ combustion ȱ technologies, ȱ is ȱ the ȱ milling ȱ and ȱ dust ȱ firing ȱ of ȱ wood ȱ pellets ȱ in ȱ large ȱ boilers.
ȱ ȱ This ȱ is ȱ exemplified ȱ by ȱ the ȱ
Avedore ȱ 2 ȱ unit ȱ in ȱ Denmark ȱ where ȱ wood ȱ pellets ȱ provide ȱ up ȱ to ȱ 70 ȱ percent ȱ of ȱ the ȱ input ȱ energy ȱ in ȱ a ȱ 590 ȱ MW ȱ electricity ȱ power ȱ station ȱ unit.
ȱȱ Wood ȱ pellet ȱ firing ȱ has ȱ become ȱ a ȱ major ȱ aspect ȱ of ȱ bioenergy, ȱ particularly ȱ in ȱ Europe.
ȱ ȱ
Co Ȭ firing ȱ or ȱ co Ȭ combustion ȱ of ȱ biomass ȱ with ȱ coal ȱ and ȱ other ȱ fossil ȱ fuels ȱ can ȱ provide ȱ a ȱ near ȱ term, ȱ low ȱ risk, ȱ low ȱ cost ȱ option ȱ for ȱ producing ȱ renewable ȱ energy ȱ while ȱ offsetting ȱ the ȱ use ȱ of ȱ fossil ȱ fuels.
ȱ ȱ Co Ȭ firing ȱ involves ȱ utilising ȱ existing ȱ power ȱ generating ȱ plants ȱ that ȱ are ȱ fired ȱ with ȱ fossil ȱ fuels ȱ (generally ȱ coal) ȱ and ȱ displacing ȱ a ȱ small ȱ proportion ȱ of ȱ the ȱ fossil ȱ fuel ȱ with ȱ renewable ȱ biomass ȱ fuels.
ȱ ȱ Biomass ȱ typically ȱ provides ȱ between ȱ 3 ȱ and ȱ 15 ȱ percent ȱ of ȱ the ȱ input ȱ energy ȱ into ȱ the ȱ power ȱ plant.
ȱȱ In ȱ this ȱ way ȱ a ȱ similar ȱ proportion ȱ of ȱ the ȱ energy ȱ produced ȱ is ȱ attributable ȱ to ȱ the ȱ renewable ȱ fuel ȱ fed ȱ into ȱ the ȱ power ȱ plant.
ȱ ȱ ȱ In ȱ general, ȱ co Ȭ firing ȱ biomass ȱ is ȱ accepted ȱ as ȱ a ȱ source ȱ of ȱ renewable ȱ energy.
ȱ ȱ However, ȱ in ȱ Australia ȱ it ȱ ȱ does ȱ not ȱ qualify ȱ as ȱ ‘Green ȱ Power’.
ȱ
Co Ȭ firing ȱ has ȱ the ȱ advantage ȱ of ȱ avoiding ȱ the ȱ construction ȱ of ȱ a ȱ new, ȱ dedicated, ȱ bioenergy ȱ plant.
ȱȱ An ȱ existing ȱ power ȱ station ȱ is ȱ modified ȱ to ȱ accept ȱ the ȱ biomass ȱ and ȱ to ȱ produce ȱ a ȱ minor ȱ proportion ȱ of ȱ its ȱ electricity ȱ from ȱ that ȱ biomass.
ȱȱ No ȱ new ȱ generating ȱ plant ȱ is ȱ needed.
ȱȱ
Besides ȱ requiring ȱ a ȱ low ȱ capital ȱ investment ȱ cost, ȱ co Ȭ fired ȱ biomass ȱ is ȱ converted ȱ into ȱ energy ȱ at ȱ a ȱ conversion ȱ efficiency ȱ essentially ȱ the ȱ same ȱ as ȱ a ȱ large, ȱ coal ȱ fired ȱ power ȱ plant, ȱ which ȱ is ȱ usually ȱ more ȱ efficient ȱ than ȱ a ȱ dedicated ȱ bioenergy ȱ plant ȱ producing ȱ the ȱ same ȱ amount ȱ of ȱ renewable ȱ energy.
ȱ
Australian Forest Growers Conference 2006
Gasification
Whereas ȱ combustion ȱ operates ȱ in ȱ an ȱ oxidising ȱ atmosphere, ȱ with ȱ excess ȱ air, ȱ gasification ȱ occurs ȱ in ȱ a ȱ reducing ȱ atmosphere, ȱ with ȱ starved ȱ air, ȱ oxygen ȱ or ȱ by ȱ steam ȱ injection.
ȱ ȱ A ȱ low ȱ or ȱ medium ȱ calorific ȱ value, ȱ combustible ȱ gas ȱ is ȱ produced, ȱ generally ȱ consisting ȱ of ȱ carbon ȱ monoxide, ȱ hydrogen, ȱ methane ȱ and ȱ low ȱ quantities ȱ of ȱ other ȱ gases.
ȱȱ After ȱ cleaning, ȱ this ȱ gas ȱ can ȱ be ȱ used ȱ to ȱ fuel ȱ spark ȱ ignition ȱ engines, ȱ be ȱ dual ȱ fired ȱ with ȱ diesel, ȱ fired ȱ in ȱ a ȱ gas ȱ turbine, ȱ or ȱ with ȱ purification ȱ it ȱ can ȱ used ȱ as ȱ a ȱ feed ȱ for ȱ fuel ȱ cells.
ȱ ȱ A ȱ number ȱ of ȱ large ȱ scale ȱ biomass ȱ gasification ȱ technologies ȱ have ȱ been ȱ trialled ȱ and ȱ are ȱ under ȱ development.
ȱȱ A ȱ prime ȱ example ȱ is ȱ a ȱ Biomass ȱ Integrated ȱ
Gasification ȱ Combined ȱ Cycle ȱ plant ȱ at ȱ
Värnämo, ȱ Sweden ȱ (see ȱ Plate ȱ 1) ȱ which ȱ has ȱ operated ȱ for ȱ several ȱ thousand ȱ hours ȱ in ȱ both ȱ gasification ȱ and ȱ full ȱ combined ȱ cycle ȱ mode.
ȱȱ
Another ȱ innovative ȱ project ȱ is ȱ the ȱ Güssing ȱ gasification ȱ combined ȱ heat ȱ and ȱ power ȱ plant ȱ in ȱ Austria, ȱ which ȱ provides ȱ 2 ȱ MWe ȱ and ȱ 4.5
ȱ
MWth ȱ energy.
ȱ ȱ There ȱ are ȱ also ȱ several ȱ sub Ȭ megawatt ȱ gasifiers ȱ on ȱ the ȱ market ȱ and ȱ these ȱ are ȱ generally ȱ used ȱ to ȱ provide ȱ fuel ȱ for ȱ furnaces ȱ and ȱ to ȱ power ȱ reciprocating ȱ engines.
ȱ
Plate 1: Värnämo BIGCC plant, Sweden.
Pyrolysis
Pyrolysis ȱ is ȱ the ȱ thermal ȱ fractionation ȱ of ȱ biomass, ȱ to ȱ produce ȱ liquid, ȱ gas ȱ and ȱ solid ȱ products.
ȱ ȱ Slow ȱ pyrolysis ȱ is ȱ well ȱ known ȱ for ȱ manufacturing ȱ charcoal.
ȱ ȱ Recent ȱ developments ȱ have ȱ been ȱ directed ȱ towards ȱ fast ȱ pyrolysis.
ȱ ȱ Fast ȱ pyrolysis ȱ is ȱ a ȱ high ȱ temperature ȱ process ȱ that ȱ converts ȱ up ȱ to ȱ 75 ȱ percent ȱ of ȱ the ȱ biomass ȱ into ȱ a ȱ liquid ȱ bio Ȭ oil, ȱ
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which ȱ has ȱ a ȱ very ȱ similar ȱ chemical ȱ elemental ȱ composition ȱ to ȱ the ȱ original ȱ biomass.
ȱ ȱ This ȱ bio Ȭ oil ȱ can ȱ be ȱ used ȱ as ȱ a ȱ fuel ȱ in ȱ a ȱ diesel ȱ engine, ȱ a ȱ gas ȱ turbine, ȱ or ȱ in ȱ a ȱ furnace, ȱ or ȱ it ȱ can ȱ be ȱ used ȱ as ȱ a ȱ renewable ȱ chemical ȱ feedstock.
ȱȱ
Bio Ȭ oil ȱ typically ȱ has ȱ a ȱ heating ȱ value, ȱ on ȱ a ȱ volume ȱ basis, ȱ of ȱ about ȱ sixty ȱ percent ȱ that ȱ of ȱ conventional ȱ fuel ȱ oil.
ȱ ȱ Canadian ȱ company, ȱ
Dynamotive ȱ has ȱ recently ȱ constructed ȱ a ȱ 100 ȱ t/d ȱ bio Ȭ oil ȱ plant ȱ in ȱ Ontario.
ȱȱ The ȱ bio Ȭ oil ȱ from ȱ this ȱ plant ȱ will ȱ power ȱ a ȱ 2.5
ȱ MW ȱ gas ȱ turbine ȱ in ȱ a ȱ ground ȱ breaking ȱ ȱ bio Ȭ oil ȱ co Ȭ generation ȱ project.
ȱ
Emerging technologies for heat and power
Technical ȱ developments ȱ have ȱ been ȱ aimed ȱ in ȱ part ȱ at ȱ developing ȱ higher ȱ efficiency, ȱ modular ȱ power ȱ systems, ȱ for ȱ the ȱ distributed ȱ power ȱ market.
ȱ ȱ These ȱ have ȱ included ȱ Stirling ȱ engines, ȱ micro Ȭ turbines ȱ in ȱ the ȱ range ȱ 30 Ȭ 120 ȱ kW ȱ and ȱ fuel ȱ cells ȱ for ȱ both ȱ stationary ȱ and ȱ transport ȱ applications.
ȱ ȱ At ȱ the ȱ present ȱ time, ȱ their ȱ application ȱ for ȱ bioenergy ȱ is ȱ either ȱ at ȱ the ȱ development ȱ or ȱ early ȱ commercial ȱ deployment ȱ stage.
ȱ
Liquid biofuels
Biomass ȱ is ȱ the ȱ only ȱ renewable ȱ energy ȱ source ȱ which ȱ can ȱ be ȱ used ȱ for ȱ not ȱ only ȱ producing ȱ heat ȱ and ȱ power, ȱ but ȱ also ȱ for ȱ liquid ȱ transportation ȱ fuels.
ȱȱ Several ȱ pathways ȱ exist.
ȱȱ
Sugars ȱ and ȱ starches ȱ in ȱ various ȱ biomass ȱ varieties ȱ can ȱ be ȱ fermented ȱ to ȱ ethanol; ȱ oil ȱ seed ȱ crops ȱ can ȱ be ȱ transestified ȱ to ȱ provide ȱ biodiesel, ȱ methanol ȱ can ȱ be ȱ synthesised ȱ from ȱ gasified ȱ biomass ȱ and ȱ a ȱ variety ȱ of ȱ synthetic ȱ fuels ȱ can ȱ be ȱ produced ȱ via ȱ Fischer Ȭ Tropsch ȱ chemical ȱ processing.
ȱ ȱ These ȱ fuels ȱ include ȱ methanol, ȱ dimethyl ȱ ether, ȱ synthetic ȱ diesel ȱ and ȱ hydrogen.
ȱ ȱ Development ȱ of ȱ liquid ȱ fuels ȱ is ȱ being ȱ driven, ȱ not ȱ only ȱ by ȱ greenhouse ȱ gas ȱ mitigation, ȱ but ȱ also ȱ by ȱ rises ȱ in ȱ the ȱ price ȱ of ȱ petroleum ȱ products ȱ and ȱ the ȱ inevitable ȱ decline ȱ in ȱ oil ȱ production.
ȱ ȱ Some ȱ research ȱ relating ȱ to ȱ hydrogen ȱ production ȱ from ȱ biomass ȱ is ȱ ongoing, ȱ although ȱ direct ȱ use ȱ of ȱ biomass ȱ is ȱ seen ȱ to ȱ be ȱ more ȱ prospective ȱ in ȱ the ȱ short ȱ to ȱ mid ȱ term.
ȱ ȱ Several ȱ companies ȱ
Australian Forest Growers Conference 2006 including ȱ Volkswagen ȱ in ȱ Germany, ȱ Volvo ȱ in ȱ
Sweden ȱ and ȱ Renault ȱ in ȱ France ȱ are ȱ involved ȱ in ȱ developing ȱ and ȱ trialing ȱ so ȱ called ȱ second ȱ generation ȱ biofuels ȱ for ȱ transportation.
ȱȱȱ
Co-products and co-values
Broadly, ȱ the ȱ socio Ȭ economic ȱ benefits ȱ of ȱ bioenergy ȱ are ȱ dependent ȱ on ȱ the ȱ nature ȱ and ȱ scale ȱ of ȱ the ȱ applicable ȱ technology ȱ and ȱ regional ȱ economic ȱ setting, ȱ but ȱ would ȱ be ȱ likely ȱ to ȱ include ȱ some ȱ or ȱ all ȱ of ȱ the ȱ following: ȱ i Support ȱ for ȱ rural ȱ and ȱ regional ȱ development , ȱ stemming ȱ rural ȱ depopulation ȱ and ȱ diversification ȱ of ȱ the ȱ local ȱ economy.
ȱ i Macroeconomic ȱ implications , ȱ including ȱ security ȱ of ȱ energy ȱ supply, ȱ increased ȱ rate ȱ of ȱ growth, ȱ risk ȱ diversification, ȱ export ȱ capability.
ȱ i Supply Ȭ side ȱ effects , ȱ including ȱ increased ȱ productivity, ȱ enhanced ȱ competitive Ȭ ness, ȱ labour ȱ and ȱ population ȱ mobility, ȱ improved ȱ infrastructure ȱ and ȱ economies ȱ of ȱ supply.
ȱ i Demand Ȭ side ȱ employment, ȱ effects , ȱ income, ȱ including induced investment ȱ and ȱ support ȱ for ȱ related ȱ ȱ ȱ industries.
ȱ ȱ Demand Ȭ side ȱ effects ȱ embrace ȱ direct ȱ effects, ȱ such ȱ as ȱ plant ȱ construction ȱ jobs; ȱ indirect ȱ effects, ȱ such ȱ as ȱ increased ȱ activity ȱ in ȱ the ȱ supply ȱ chain ȱ which ȱ provides ȱ materials ȱ and ȱ services ȱ to ȱ build ȱ the ȱ plant; ȱ induced ȱ effects ȱ stemming ȱ from ȱ successive ȱ expenditure ȱ linked ȱ to ȱ the ȱ construction ȱ and ȱ operation ȱ of ȱ the ȱ plant; ȱ and ȱ displacement ȱ effects ȱ which ȱ reduce ȱ the ȱ demand ȱ for ȱ competing ȱ activities.
ȱ ȱ
A ȱ well ȱ managed ȱ bioenergy ȱ project ȱ could ȱ also ȱ have ȱ benefits ȱ related ȱ to: ȱ mitigation ȱ of ȱ dryland ȱ salinity, ȱ enhancement ȱ of ȱ animal ȱ habitats ȱ and ȱ biodiversity, ȱ management ȱ of ȱ wastes, ȱ weed ȱ management, ȱ co Ȭ production ȱ of ȱ products ȱ such ȱ as ȱ activated ȱ carbon ȱ and ȱ biofertilisers, ȱ saleable ȱ ash ȱ and ȱ odour ȱ
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reduction ȱ (from ȱ better ȱ management ȱ of ȱ animal ȱ manures).
ȱ
The Australian bioenergy industry
There ȱ is ȱ currently ȱ close ȱ to ȱ 600 ȱ MW ȱ of ȱ bioelectricity ȱ capacity ȱ in ȱ Australia, ȱ with ȱ the ȱ dominant ȱ contributions ȱ being ȱ from ȱ sugar ȱ cane ȱ bagasse, ȱ land Ȭ fill ȱ gas, ȱ sewage ȱ gas ȱ and ȱ black ȱ liquor.
ȱ ȱ Some ȱ of ȱ the ȱ established ȱ generating ȱ companies ȱ are ȱ co Ȭ firing ȱ biomass ȱ with ȱ coal ȱ in ȱ large ȱ utility ȱ boilers.
ȱ ȱ Bioenergy ȱ
Australia, ȱ an ȱ alliance ȱ of ȱ government ȱ and ȱ industry ȱ organisations ȱ acts ȱ as ȱ a ȱ forum ȱ for ȱ fostering ȱ bioenergy ȱ developments ȱ in ȱ
Australia ȱ (
).
ȱȱȱȱȱȱ
Conclusions
Bioenergy ȱ has ȱ a ȱ huge ȱ role ȱ to ȱ play ȱ in ȱ the ȱ provision ȱ of ȱ sustainable ȱ energy.
ȱ ȱ The ȱ Clean ȱ
Energy ȱ Future ȱ for ȱ Australia ȱ study ȱ (WWF ȱ
2004) ȱ identified ȱ that ȱ greenhouse ȱ gas ȱ emission ȱ reductions ȱ of ȱ some ȱ 70% ȱ could ȱ be ȱ achieved ȱ by ȱ
2040 ȱ using ȱ several ȱ existing ȱ technologies ȱ and ȱ processes.
ȱ ȱ The ȱ study ȱ found ȱ that ȱ bioenergy ȱ ȱ could ȱ play ȱ a ȱ crucial ȱ role, ȱ providing ȱ 29% ȱ of ȱ the ȱ total ȱ energy ȱ supply ȱ mix.
ȱ ȱ However, ȱ bioenergy’s ȱ potential ȱ in ȱ Australia ȱ is ȱ yet ȱ to ȱ be ȱ realised ȱ and ȱ its ȱ fortunes ȱ will ȱ be ȱ dictated ȱ by ȱ incentives ȱ such ȱ as ȱ the ȱ Federal ȱ Government’s ȱ
Mandatory ȱ Renewable ȱ Energy ȱ Target ȱ and ȱ various ȱ state ȱ government ȱ requirements ȱ for ȱ greenhouse ȱ gas ȱ mitigation.
ȱ
References
BCSE, ȱ 2004.
ȱ ȱ Renewable ȱ Energy ȱ Power ȱ Plant ȱ
Register ȱ 2004.
ȱ
.
ȱȱ
DTI ȱ (Department ȱ of ȱ Trade ȱ and ȱ Industry) ȱ 1999, ȱ
New ȱ and ȱ Renewable ȱ Energy: ȱ Prospects ȱ in ȱ the ȱ
UK ȱ for ȱ the ȱ 21 st ȱ Century, ȱ Supporting ȱ Analysis , ȱ
Annex ȱ B, ȱ 258.
ȱ
International ȱ Energy ȱ Agency ȱ Statistics, ȱ
Renewables ȱ Information ȱ 2005 ȱ with ȱ 2004 ȱ
Data.
ȱȱ
.
ȱȱ
WWF, ȱ 2004.
ȱ ȱ Clean ȱ Energy ȱ Future ȱ for ȱ Australia, ȱ
WWF ȱ Australia.
ȱ
.
ȱȱ
Contact
Dr ȱ Stephen ȱ Schuck ȱ
Bioenergy ȱ Australia ȱ
7 ȱ Grassmere ȱ Road ȱ
Killara ȱ
NSW ȱȱȱȱȱȱȱȱȱȱ 2071 ȱ
Phone: ȱ (02) ȱ 9416 ȱ 9246 ȱ
Email: ȱ
ȱ ȱ
Web ȱ : ȱȱ
.
ȱ
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