Biofuels Production & Environmental Impacts: A European perspective Graeme Walker
www.abertay.ac.uk
Federation of Latin American Chemical Societies Meeting July, 2008
Outline • • • • •
European Biofuels: overview Bioethanol: pros & cons, environmental impact Bioethanol: current processes, future challenges & opportunities Bioethanol from lignocellulose Conclusions & future prospects
Why biofuels?
Environment
Fuel Security
Agriculture
European Biofuels The 20:20 goal = 20% renewables by 2020 • Biogas (Anaerobic Bacteria) Current production • Biodiesel (Brassica napus, Animal/veg oils) • Bioethanol (Yeast)
• Biohydrogen (Cyanobacteria, Clostridia, PNS Research & Development
bacteria)
• Bio-oil (Botryococcus braunii, other microalgae) • Biobutanol (C.butylicum, C.acetobutylicum)
Biodiesel in Europe • Biodiesel accounts for 76% of total biofuel consumed in the EU • EU biodiesel production set to increase by 55% in 2008 to 16Mt (European Biodiesel Board) • But, in 6 EU countries, biodiesel production has fallen since 2006 (due to higher feedstock prices and subsidised imports from USA)
Bioethanol: Global Consumption [Note: All Biofuels expected to account for 8.5% of global energy use by 2030 – US Energy Information Administration]
Projected Fuel Ethanol Consumption. Source: IEA 140000 120000
Million Litres
100000 80000 60000 40000 20000 0 1975
1980
1985
1990
1995
2000
2005
Year Brazil
US & Canada
EU
World
2010
2015
2020
European bioethanol? 400
millionL
2006
350
Substrates: - Sugarbeet
Spain Germany France Poland Italy Sweden Hungary Lithuania Czech R Holand Latvia
300
250
200
- Wheat
150 100
50
0
Country
Biofuels in the UK (HGCA Newsletter 2/4/08)
• So far, UK biofuel production is much less than the amount required to fulfil the RTFO target (5% by 2010) • Currently biofuels only account for a small percentage of the UK fuel market, a mere 0.70%. • There is presently only one ethanol plant in operation (British Sugar, production capacity of 55,000t). • This would suggest that total UK biofuel production for 2007 was around a quarter of a million tonnes.
British bioethanol (1936)
Why Bioethanol? [Climate saviour or climate pariah?]
Pros CO2 neutral Reduced dependence on oil Agricultural diversification Clean burning, low toxicity Less GHG emissions (~65% less) Higher flash points (better fire safety) Better biodegradability Co-generation of electricity
Cons Food-to-fuel Lower oil price Sustainability Energy balance Residues, emissions Inefficient microbes Hydroscopic Less mpg
Bioethanol: current substrates?
Brazilian ethanol programme (Proalcool*) SUGAR CANE
Bagasse
Ethanol Sugar CO2
Animal feed, Fuel electricity *~380 Distilleries in Brazil >24bn litres ethanol/yr [40% of transport fuel]
>700,000 jobs created >$2bn savings pa.
Fusel oil Vinasse
Food Chemicals
Biogas
Yeast
Animal feed
USA Bioethanol processes (Gasahol) CORN (maize)
Crude starch Microbial amylases Syrup conversion Yeast Fermentation Distillation By the end of 2007, U.S. will have processed 3 bn bushels of corn for ethanol = 30.28 billion liters
GASAHOL
Bioethanol Scientific & technological challenges (especially from lignocellulosic feedstocks)
NOTE: lignocellulosic ethanol production/consumption estimated to result in 75-80% Green-House-Gas emissions reduction compared with gasoline
Second-generation bioethanol: some potential cellulosic (non-food) feedstocks • • • • • • •
Wood chips/sawdust/forestry residues/SRC Waste paper Corn fibre/cobs/stover Municipal Solid Waste, MSW Straw, bagasse Cereal hulls/spent grains “Energy crops” (Switchgrass, Miscanthus, Ryegrass, etc.)
• Cyanobacterial cellulose
Some cellulose-to-ethanol plants (USA) • • • • • •
New York & Michigan (wood chips – Mascoma) Tennessee (switchgrass – Mascoma) Maine (wood chips – RSE Pulp & Chemical) Kentucky (corncobs – Ecofin/Alltech Inc) Louisiana (bagasse – Celunol) Ohio (corn fibre – Genahol)
Selected international others: Iogen (straw – Canada); Abengoa (straw – Spain, US); Etek (softwood – Sweden); Elsam (straw –Denmark); TMO (straw/wastepaper– UK); NEDO (rice straw – Japan); Tavda (wood – Russia); Mossi & Chistophi (sorghum fibre – Italy)
Lignocellulosic bioethanol – key areas for improvement • Cellulose hydrolysis – Steam explosion, acids, enzymes (cellulases, arabinozylanases, ligninases) – New pre-treatments: ozonolysis+ultrasound? – SSF (e.g. Thermoanaerobacterium saccharolyticum)
• Fermentation – – – –
Xylose fermenting yeasts or bacteria Very high gravity wort (>20%v/v ethanol) Thermotolerant/alcohol tolerant/inhibitor tolerant yeasts Optimised nutrition (esp. metal ions like Mg, Zn)
• Distillation – Anhydrous ethanol (molecular sieves, azeotropes, membrane pervaproation) – Energy balances!
Second-generation bioethanol: research challenges Lignocellulosic material
1 Pretreatment Pre-hydrolysis [physico-chemical]
Hydrolysis [biological]
Fermentation (hexose)
2
Distillation 3 BIOETHANOL
Fermentation (pentose)
4 Energy
Ethanologenic yeasts Feedstock
Fermentable substrate
-Wheat, Maize, Barley -Sugarcane/Beet
Starch hydrolysate (maltose, glucose) Sucrose
-Potato, Rice
Starch hydrolysate (maltose, glucose) Saccharomyces Inulin hydrolysate (fructose) Kluyveromyces Lactose Kluyveromyces Starch Schwanniomyces Laminarin (glucose) Pichia angophorae Xylose, arabinose, glucose, Pichia, Candida, cellobiose Pachysolen, Kluyveromyces GM S.cerevisiae
-Agave/Artichoke -Cheese whey -Raw starch -Seaweed -Paper, sawdust, straw, wood, spent grains, cornsteep liquor, paper, rapeseed residues, MSW, bagasse, corn fibre
Yeasts* Saccharomyces Saccharomyces
*Other microbes? Zymomonas, E. coli (GM), Klebsiella (GM), Bacillus (GM), Thermoanaerobacterium saccharolyticum
Saccharomyces cerevisiae strains cannot ferment pentose sugars as D-xylose and Larabinose. Too bad, because… •Grass •Corn stover •Wheat bran •Barley husks
(16% xylan, 5% arabinan) (19% xylan, 3% arabinan) (19% xylan, 15% arabinan) (20% xylan, 9% arabinan)
Xylose fermentation pathway Xylose XR
Xylose isomerase
Xylitol
Bacteria, Piromyces
XDH
Xylulose
• • • • • • • • •
S. cerevisiae
ETHANOL
Brettanomyces naardenensis Candida intermedia var intermedia Candida lyxosophila Candida shehatae var. lignosa Candida tenuis Cryptococcus albidus Kluyveromyces marxianus Pachysolen tannophilus Pichia stipitis
The yeast message • Yeasts are extremely diverse physiologically (but yeast biodiversity virtually untapped)
• S.cerevisiae is a rather exceptional yeast and may not be the best for bioethanol (xylose non-fermenter) • We need more knowledge of yeast cell physiology (Especially in non-Saccharomyces yeasts)
• Yeast stress is a dilemma (e.g. ethanol tolerance) • Bacteria are competitive
Bioethanol from spent grains?
???
Spent grains are cereal residues from breweries and distilleries 2006 figures Whisky Production (x106 L p.a.)
Yield alcohol (L/t)
Residues (1000 t dry matter)
Grain (wheat or maize)
273
490
209
Malt (barley)
170
531
135
Scottish grain and malt distilleries
Lager brewery
85% malt 15% wheat
Grain distillery
86% maize 14% malt
Ale brewery
96% malt 4% roasted malt
Malt distillery
100% malt
Bioethanol from spent grain: Current Research Pretreatment Pre-hydrolysis −Ale (malt) − Lager (malt +
Enzyme Hydrolysis
wheat)
1. 2. 3. 4.
Temp? Acids? Novel pre-treatments? Enzymes Characterisation of sugars, inhibitors
−Whisky (malt) −Spirit (maize + malt)
Fermentation (Glucose, xylose, arabinose) • C6 & C5 sugars
• P. stipitis, K. marxianus etc.
Distillation
BIOETHANOL
“Potential” bioethanol from UK spent grains British Breweries (2007)
Scottish Distilleries (2007)
• 210,974 tonnes SG • Would yield: 21M litres bioethanol
• 297,000 tonnes SG • Would yield 20.5M litres bioethanol
NOTE: Existing (lab-based) process is inefficient (hydrolysis and Pichia or Kluyveromyces fermentation ~20%CE)
- estimated potential >100M litres/year
Novel lignocellulose pre-treatment technology?
• Ultrasound (20 kHz-1 MHz)
+ • Ozonolysis (O3)
CH2OH O
CH2OH O
O. +
O3 H2O 2HO .
O2 + O . oxygen atom
OH
(1)
O OH
O
CH2OH
(1)
OH
O
CH2OH
(2)
2HO . hydroxyl radical H2O2 hydrogen peroxide
O
OH
O
HO. hydroxyl radical
(2)
O
OH O
OH
O
O OH
CH2OH
CH2OH O
CH2OH O
O
O OH
O OH
O
CH2OH
O
OH
O
OH O OH
O O
Conclusions & future prospects • • • • •
Global biofuels increasing rapidly Europe is lagging behind (esp. bioethanol in UK) Yeast biodiversity is untapped for fermentation New lignocellulosic pre-treatments required Plentiful biowaste available (eg. spent grains, straw, wood, corn residues, paper etc.)
• 2nd-generation bioethanol is the way forward!
Acknowledgements • Abertay University
Yeast Group
(Raffaele De Nicola, Jane White, Biju Yohannan, Stelios Logothetis, Irma Ochigava, Paola Bruno, Jason McColm, Jason Bennett, David Bremner, Rashmi Chand)
• Royal Society of Chemistry, FLAQS organisers
Thank you!
