51 biofuel production
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Biofuel Production
Prof. Tony Bridgwater
Bioenergy Research Group
Aston University, Birmingham B4 7ET
AV Bridgwater 2008
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Biomass
Carbohydrates e.g. corn, wheat
Sugarfrom cane or beet
Vegetable oil e.g. rape, palm, soy, jatropha
Lignocellulosics (lignin, cellulose and hemicellulose)e.g. wood, grass, straw, residues
Fertiliser and other inputs have a major impact on thesustainability of crops. Lignocellulosics generally have alower requirement.
There are many agronomical criteria for crop selection ofwhich yield (dry t / ha.y) is important for maximising use
of land
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Biofuels
Oxygenates
Methanol Ethanol
Butanol Mixed alcohols Dimethyl ether
Hydrocarbons Biodiesel Synthetic diesel
Synthetic gasoline Methane (CSNG)Other
Hydrogen
Generation
2G1G & 2G
1G & 2G2G2G
1G2G
2G1G & 2G
1G & 2G
First generation (1G)biofuels are from food suchas:
Ethanol from sugar, corn Biodiesel from rape oil
Second generation (2G)biofuels are from wholecrops such as wood andgrasses:
Synthetic diesel Methanol Ethanol
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Feeds, processes, products
Thermalconversion
Esterification
Ethanol,Butanol,
Chemicals
Biodiesel(FAME,RME)
Chemicals
Synthetic H/C,Ethanol, Butanol
Methanol,Chemicals
Power, Heat
Starch & sugars Oil plants
Biologicalconversion
Residues ResiduesLignocellulose
1G1G2G 2G
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1st and 2nd generation biofuels
First generation biofuels are from foodstuffs such as:
Ethanol from sugar, wheat or corn about 2 t/ha/y inEurope and USA, up to 6 t/ha/y from sugar cane in Brazil
Biodiesel from vegetable oils about 1 t/ha/yThese are important in introducing biofuels and increasingawareness.
Second generation biofuels are from whole crops such aswood, energy crops, residues, such as:
Synthetic diesel about 4 t/ha/y
Methanol about 8 t/ha/y Ethanol about 5 t/ha/yHigher yields and absence of competition with food give
these a longer term future
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Feeds, processes, products
Thermalconversion
Esterification
Ethanol,Butanol,
Chemicals
Biodiesel(FAME,RME)
Chemicals
Synthetic H/C,Ethanol, Butanol
Methanol,Chemicals
Power, Heat
Starch & sugars Oil plants
Biologicalconversion
ResiduesLignocellulose
Residues
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Bioethanol 5% limit in gasoline in Europe for cars (E5).
E85 (85% ethanol) is used in USA and E100 in Brazil
Concerns:
Logistical and market compatibility Vapour pressure
Hygroscopicity andlow temperature properties Materials compatibility
Low energy density ~1/3 Fuel compatibility
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Bioethanol technologyBiological processes
Mature technology for 1G from sugar, grain and corn.
Developing technology for 2G from lignocellulosics.
Hydrolysis releases C6 & C5 sugars, separates lignin. C6 sugars fermentation is commercial. C5 sugars fermentation needs to be demonstrated
Lignin needs to be utilised for energy efficiency In 1G technology, more energy is often input than is
derived in the ethanol, and significant improvements are
needed.Thermal processes
Commercial but mixed product with other alcohols.
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2 Generation bio-ethanol
Sugars
Byproducts
ResiduesWastesDistillation
Bioethanol
Hydrolysis
Syngas
Ethanol synthesis
Thermal Gasification
Syngas
Fermentation
Other alcohols
Biomass
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Feeds, processes, products
Thermalconversion
Esterification
Ethanol,Butanol,
Chemicals
Biodiesel(FAME,RME)
Chemicals
Synthetic H/C,Ethanol, Butanol
Methanol,Chemicals
Power, Heat
Starch & sugars Oil plants
Biologicalconversion
Residues ResiduesLignocellulose
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Biodiesel
Methyl esters of vegetable oil e.g. rape, soy, palm,sunflower to reduce viscosity and improve otherproperties.
The process is lowtemperature and catalytic:batch, semi-batch, semi-continuous, or continuous
Byproduct glycerine needsto be used
Concerns
Different oil sources result in different quality productsthat is difficult to control
Low temperature performance is variable and poor
Limited to 5% in diesel for vehicles in Europe due tomaterials and compatibility concerns
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Current status 1st generation Bioethanol is attractive as the technology is available
commercially Concerns over properties and energy density
Biological 1G technology from corn has low efficiency Biological 2G has some development challenges Thermal 2G gives mixed alcohol product
Biodiesel is attractive as a motor fuel as it can be readilyblended with diesel The quality is variable Low temperature characteristics are variable and poor Low yields and crops have high energy inputs
Competition of food vs fuel has led to high food price rises; There is also competition for land and sustainability issues
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Feeds, processes, products
Thermalconversion
Esterification
Ethanol,Butanol,
Chemicals
Biodiesel(FAME,RME)
Chemicals
Synthetic H/C,Ethanol, Butanol
Methanol,Chemicals
Power, Heat
Starch & sugars Oil plants
Biologicalconversion
ResiduesResiduesLignocellulose
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Synthetic hydrocarbons
Synthetic hydrocarbons include diesel, gasoline, kerosene
They are entirely compatible with conventional fuels in all
proportions, but are much cleaner. At least in the medium term, these are likely to be the
biofuels of choice due to their ease of assimilation into
markets, familiarity by the vehicle industry and consumers,energy density,
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Routes to 2nd G hydrocarbons
1. Thermal gasification
a) + Fischer Tropsch
b) + Methanol synthesis + upgrading by MTG or MOGD2. Pyrolysis + upgrading
a) by hydro-processing
b) by zeolites3. Hydro-processing vegetable oil
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Syngas
1: Biofuels via thermal gasification
Biomass
Solid Biomass Gasification
Fischer Tropsch
MTG
Conventional synthetic gasoline and diesel
Mt synfuelMOGD
Refining
Methanol
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Challenges
The process most commonly considered is thermalgasification to clean syngas and synthesis of hydrocarbonsby Fischer-Tropsch (FT)
Biomass is a widely dispersed resource that must betransported over large distances at significant cost.
Biomass preparation for entrained flow gasification can be:
Torrefaction to render biomass more friable for grinding Liquefaction by fast pyrolysis
Gasification technology is unproven at large scale.
Gas cleaning is a major challenge and unproven The minimum economic size of Fischer Tropsch is widely
considered to be 20,000 bbl/day or nearly 1 million t/y
biofuels requiring nearly 5 million t/y biomass.
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Fischer Tropsch
Syngas
Pretreatment by pyrolysis
MTG
Conventional synthetic gasoline and diesel
Fast pyrolysis
75% wt. liquid
Gasification
Torrefaction
85% wt. solid
Biomass
Mt synfuelMOGD
Refining
Methanol
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Pretreatment Torrefaction is low temperature pyrolysis to dry and
partially devolatilise biomass. The product yield isaround 85% and can be more readily ground like coalfor gasification.
Fast pyrolysis produces a mobile liquid (bio-oil) with upto 10 times the energy density of biomass. The productyield is up to 75%
Liquids are easier to handle, store and transport. Fast pyrolysis can be decentralised and located nearthe biomass resources
Conversion of biomass to a liquid near sourcereduces transport costs, and reduces gasificationcosts.
Pressurised oxygen gasification of liquids is easier
and lower cost than solid biomass
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Pyrolysis + Fischer Tropsch
Gasn.
F-T
Biomass
Biomass
Biomass
Biomass
Biomass
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Capital costs
0
2000
4000
6000
8000
10000
12000
14000
16000
0 2 4 6 8 10 12
Pyrolysis + large FT
Small gasification +small FT
Biomass input million dry t/y
Capital cost, million
Large gasification + FT
Small FTunproven
Large
gasificationunproven
Small pyrolysis& large FT
proven
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Solid vs liquid gasification
Capital cost increase of ~10% due to diseconomies ofscale in small pyrolysis plants
Capital cost reduction of ~15% due to lower feedhandling costs
Capital cost reduction of ~10% due to lower costs infeeding a liquid to a gasifier at pressure compared tosolid biomass
Cost reduction of ~10% from absence of alkali metalsslagging and erosion
Efficiency loss of ~5% due to additional processing step
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Methanol based processes
Methanol well established technology from natural gas.
MTG (Methanol To Gasoline) commercial technologyproven in New Zealand from naturalgas. High yield and high efficiency
MOGD (Methanol to Olefins, Gasolineand Diesel) well researched tech-nology. High yield and high efficiency
Mt synfuel new process via propylene
Methanol, MTG etc are moreselective than FT and potentially giveup to 30% higher yields (from ~50%to ~65% on an energy basis)
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2: Upgrading bio-oil directly
Production of hydrocarbons requires rejection of the oxygen: Hydro-processing rejects oxygen as H2O
C1H1.33O0.43 + 0.77 H2 CH2 + 0.43 H2O
Separate process, requires hydrogen, high pressure Gives projected yield of around 25% naphtha-likeproduct for refining, without H2 or 15% with H2
Zeolite cracking rejects oxygen as CO2 C1H1.33O0.43 + 0.13 O2 0.66 CH2 + 0.34 CO2 Close coupled process requiring constant catalyst
regeneration.
No hydrogen requirement, no pressure Gives projected yield of around 20% aromatics
Feeding to conventional refinery provides quality
control and economies of scale
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Costs of upgraded bio-oil
Yield,wt%
/tproduct
HHV,GJ/t
/GJproduct
/toe
Wood feed (daf) 100 67 20 3 145Pyrolysis oil output 70 147 19 8 331
Diesel (EXCL H2) 23 592 44 13 578
Diesel (INCL H2 from biomass) 13 880 44 20 860
Gasoline 22 453 44 10 443
FT diesel * # 20 1362 42 1395
MTG gasoline * 26 43
Crude oil at $100/bbl - 560 43 15 560
Basis: 1000 t/d daf wood feed at 67 /dry t, 2006 except *# DENA report 2006
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3: Hydro-processing vegetable oil
Bio-diesel (by esterification of crude vegetable oil) iscurrently limited to 5% of conventional diesel.
Vegetable oil can be hydroprocessed to synthetic dieseland Neste have built a 100,000 t/y plant in Finland basedon palm oil and other vegetable oils. Other plants areunder construction
Generation 1 as feed is a foodstuff and product is 2nd
generation equivalent
The hydrogen requirement is much less than fast
pyrolysis liquid, but the vegetable oil productivity,sustainability and food competition issues remain.
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Thermal process summary
Conventional gasoline and diesel
Refining
Methanol
synthesis
MTG MOGD
Syngas
Liquidbio-oil
Mt-
Synfuels
Biomass
Gasification Zeolitecracking
Hydro-treating
FischerTropsch
synthesis
Liquid
bio-oil
Fast pyrolysis
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Challenges Improve crop yields and characteristics Improve 1st and 2nd generation bioethanol technology Improve lignocellulosics pretreatment for 2nd generation
Demonstrate C5 fermentation Demonstrate large scale thermal gasification Demonstrate large scale gas cleaning & conditioning
Demonstrate small scale hydrocarbon synthesis Demonstrate fast pyrolysis liquids upgrading Develop integrated biorefineries Improve catalysts Match catalysts to biomass derived primary products Robustly compare alternative systems Reduce costs
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Thank you
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