Challenges in Renewable Biofuel Production

Transcription

1 2012 MIT-Europe Energy Conference Rome March 28-29, 2012 Challenges in Renewable Biofuel Production Gregory Stephanopoulos MIT

2 Types of biofuels and biofuel feedstocks Ethanol from corn Biodiesel from plant seeds and vegetable oils Ethanol from sugarcane Other feedstocks (not competing with food): cellulosics, algae, synthesis gas Other biofuels than ethanol (butanol, lipids, hydrocarbons)

3 Examples of advanced biofuels Other higher alcohols: butanol, isobutanol, propanol, pentanol, Longer, branched alcohols (3-Methyl-1-Butanol) Hydrocarbons of any type Oils (C16, C18) Methyl, ethyl esters of fatty acids (FAME=biodiesel) Isoprenoid pathway products: Isopentenol, farnesene Jet fuel Isooctane

4 Difference between Ethanol and all the others We can make ethanol

5 Bio-fuels: Primarily a feedstock story Produced either from Biomass, or, Any feedstock by biological methods

6 Summary of the state-of-the-art in biofuel development (in 4 slides)

7 1. Sugar platform Starches (Corn) Biomass deconstruction still challenging Easy conversion Sugars Sugarcane Hydrolysates of plentiful biomass-algae Straightforward with yeast Ethanol Advanced biofuels Requires Metabolic Engineering

8 Plentiful Biomass?

9 How much biomass is there? BTS (DOE): 1.37 billion tons/year NAE-NRC study on Alternative Fuels: Feedstock type Current amount By 2020 (million tons) Corn stover Wheat and grass straw Hay Total cropland biomass Dedicated biofuel crops Woody biomass Paper and paperboard Animal manure 6 12 Municipal solid waste TOTAL

10 Potential of biofuels (USA) gallons ethanol/dry ton of biomass B gallons Ethanol/year or B gallons of gasoline equivalent 20-30% of gasoline used (1 ton of ethanol = 333 gallons, or 1 Gallon = 3 kgs, or 1 B Gallons = 3 M tons) Potential is greater when advanced biofuels are produced such as biobutanol or biodielsel

11 Sophisticated pathway and microbe engineering is required to create biocatalysts for converting sugars to advanced biofuels Coupled with Advanced bioprocessing (isobutanol)

12 Pentanol Synthesis Challenges: 1. Supply of building block (Propionyl- CoA) 2. Condensa?on reac?on of C2 + C3 3. Acceptance of 5- carbon substrates for the rest of pathway enzymes 12

13 Biofuels toolkit Thiolase Dehydrogenase & Dehydratase Mutase Reductase 13

14 Biofuels toolkit 14

15 Advanced metabolic engineering Allows biosynthesis in microbes of almost any fuel or chemical, natural or not 15

16 Cells: Little chemical factories with thousands of chemical compounds interconverted through thousands of chemical reactions Main substrate: Sugars Products: Virtually infinite

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18 Redirecting Carbon Flux CoA remover CoA activator P 4 Substrates Rxn 1 Rxn 2 Rxn 3 Rxn 4 Rxn 5 Rxn 6? Pentanol P 2 P 4 HPLC analysis 18

19 2. Biofuel production by direct photosynthesis Sun Metabolic Engineering; Secretion? Oil recovery Oil-alkane production Algae Just growth Biomass Productivities are high but cultures very dilute Key challenge: Cost-effective dewatering Other biofuels (ethanol)

20 Algae Gallons GE/acre/year Soybeans 48 Sesame 74 Jatropha 202 (50?) Cellulosic ethanol 533 Sugarcane ethanol 566 Algae ~6,000 However, to produce 1 gallon of oil one must move around ~2,000 gallons or water

21 3. Biodiesel Oils Biodiesel (FAME) Simple trans-esterification reaction Key issues: Feedstock cost and availability

22 3. Biodiesel Key points: It is a bad idea to use vegetable oils for biodiesel Sustainable biodiesel production MUST be based on carbohydrates Gallons GE/acre/year Soybeans 48 Sesame 74 Jatropha 202 Cellulosic ethanol 533 Sugarcane ethanol 566 Algae ~6,000 Need organisms capable of converting sugars to fats and lipids (or Free Fatty Acids, FFA)

23 Recombinant Some results on recombinant oil producing microbe Lipid production Wild type FAME (g/l) Patent pending Total sugar consumed: 312 g/l Total oil produced: 80g/L in 72 hours Yield: 29.4% Theoretical Maximum Yield: 31%

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25 A tripod of feedstock and products Feedstock: Glucose/sugar (1 kg) Product: Ethanol (~0.51 kg) Amounts of two products are energetically equivalent (possible due to the almost theoretical yield of our microbe) Product: Fats/Oils (0.31 kg)

26 Electrofuels (They can increase the yield of solar energy conversion by an order of magnitude relatively to photosynthetic systems)

27 The Electrofuels FOA was released in Dec in response to a need for more efficient biofuel production technologies Photosynthesis Biomass Algae Electrons/ Reducing equivalents Electrofuels Chemical Catalysis Biological Catalysis EtOH, Pyrolysis Biodiesel, Advanced oils Advanced biofuels biofuels Syngas, CH 3 OH, CH Advanced 4, Advanced fuels? Fuels 27

28 Bio-GTL OIL Aerobic oil production from CO 2 product O 2 Recycled CO 2 Product of CO 2 fixation H 2 O Split Anaerobic CO 2 reduction H 2 New CO 2 Goal: Produce an infrastructure compatible fuel (biodiesel) from CO 2 and CO/H 2 Asset: Oleaginous microbe with extremely high yields, productivities, and titers Strategy: Fix CO 2 with CO/H 2 in acetogenic bacteria or Clostridia and/or via rmfc and feed acetate so produced to Oleaginous microbe Challenges: Achieve high rates of growth of acetogenic bacteria, and acetate produc n

29 Supporting Evidence Growth and acetate production of Acetobacterium woodii on fructose and H 2 /CO 2 Preliminary Calculations: Acetate Productivity: 2.4 g/ L/day (0.1 g/l/h) g oil/g acetate 3.33 Kg OIL/Gal ~170 Million gals of fermentor capacity required for a 50Mgal/ year oil plant O.D x lower of a typical EtOH fermentation Specific rate g/g/hour comparable to ethanol

30 Main Challenges Main Challenge 1: Improve oil production from acetate: g/l at yields greater than 80% of theoretical maximum and productivities of g/l/h Main Challenge 2: Increase Volumetric Productivity of acetate production by ~ 15 fold

31 4. Bio-GTL Natural gas Steel mills Clostridia (Koskata, AlzaTech) Ethanol SynGas Acetogens (Moorella) Acetate OIL Gasification of biomass, MSW, coal Expensive gasifiers Advanced biofuels via Metabolic Engineering

32 Acetyl-CoA Metabolic pathway Methyl Branch ATP CO 2 2e - 2e - 2e - 2e - 2H + + 2e - Hydrogenase Acetyl-CoA Synthase H 2 CO 2 CODH 2e - CO Carbonyl Branch 2e - Acetyl CoA 2e - Acetaldehyde Ethanol Acetyl - PO 2-3 ATP Acetic Acid Isobutanol and other biofuels

33 Electron production Acetyl-CoA pathway 2 CO e - C 2 H 4 O 2 hydrogenase H 2 2 H e -1 4 moles needed If electrons from H 2 CODH CO + H 2 O CO H e -1 2 CO H 2 C 2 H 4 O H 2 O If electrons from CO 4 CO + 2 H 2 O C 2 H 4 O CO 2

34 Gas fermentation challenge: solubility Species C* (mm) CO 2 48 CO 1.2 H 2 0 C, P=1 atm. Strategies: 1. Closed bioreactor: High pressure 2. Continuous-gas bioreactor: High mass transfer rate

35 Summary of k L a Reactor Diffuser Agitation (rmp) k L a (1/hr) Stirred tube Column tube NA 13.2 Column Micro bubble NA 25.8

36 Carbon utilization: Experiment 1 Total Carbon (g/l) Time (hr) Carbon utilized-exp 2 CO availability-exp 2 CO2 availability N Utilization = 0.5 cell mass C acetate (g/l) A = k L a( C Availability of Gas = 12 k L a C * (g/l/hr) * C t )

37 Carbon utilization: Experiments 2,3 30 Total Carbon (g/l) Time (hr) Carbon utilized-exp 1 Carbon utilized-exp 2 CO availability-exp 1 CO availability-exp 2 CO2 availability Gas fermentation is limited by CO availability 4 CO + 2 H 2 O C 2 H 4 O CO 2

38 Experimental summary-acetogens Feedstock Acetate (g/l) Productivity (g/l-hr) CO 2, CO, H CO 2, CO CO Glucose, Syngas Glucose, CO Electron donors: H 2, CO, glucose Electron acceptor: CO 2

39 The future of biofuels: Take away points 1. Corn ethanol will max out at ~15B Gallons/year 2. Biomass supply: Sufficient for B GGE without stressing the food supply 3. Cellulosic ethanol: Slow in coming. Several plants under deployment 4. Cellulosic ethanol: Interplay of biomass deconstruction technologies and cost of biomass 5. Cellulosic ethanol: Negative interaction between supply chain development and technology development 6. Butanol: Will do well if the E10 wall is maintained. Main advantage seems to be low volatiles

40 The future of biofuels: Take away points (cont d) 7. Drop-in biofuels: Unnecessary. Aim for maximum costeffectiveness 8. Algae: Were promoted on the basis of productivity and notland based. Key is cost-effective dewatering technologies 9. Great need: High density biodiesel and jet fuel 10. Biodiesel: Production from oils and vegetable seeds is costly and unacceptable environmentally 11. Great promise: Technologies for converting renewable feedstocks (sugars, biomass) to oil 12. Novel Bio-GTL technologies are promising

41 The end Questions?

42 Summary: Bio-GTL technology Co-products Marketing such compounds as, higher-priced, chemicals

43 What is the likelihood that one of the advanced biofuels will compete successfully with ethanol? Consider: Yields (gallons ethanol/kg sugar) is most important metric for economical process Ethanol is produced at almost maximum theoretical yield Ethanol has low energy density, i.e., very low cost per volume

44 Some calculations 1 Gallon of biodiesel = 3.8 Liters = 3.4 Kgs can be produced from 3.4 / 0.31 = 11 Kgs of Glucose that costs ~ $ Hence, biodiesel can be produced from sugars at an estimated total cost of $ Probably less with other feedstocks that have potential for drastically lower cost

45 2L fermenter YL- Eng- OD YL- Wild- OD 200 OD Hours

46 140 2L bioreactor with C5 Hz with 200g/l sugars TAG/Sugar g/l TAG Sugar consumed Mutant1 CB+Hemo+Glut1 Mutant strains Mutant2 D9+CB+Hemo+Glut1

47 72 hour fermentation. C5 Xz supplemented with 200g/L of glucose. Yield for mutant 3 is 41/155 = 26.5% Mutant 1 Mutant 2 Mutant 3

48 Some calculations with corn ethanol ~10.6 B gallons of ethanol estimated produced in US from corn in 2009 [at current production] This is equivalent to ~8 B gallons gasoline It takes units of fossil energy to produce 1 unit of energy in fuel ethanol The 10.6 B gallons of ethanol displace ~2 B gallons of petroleum, or ~1.5% of US needs It takes >30% of the US corn production to produce the 10.6 B gallons of ethanol

49 Where is this biomass?

50 Coal does not come easy 1.1 Billion tons mined per year Gillette Coal field (Wyoming): 80 miles strip with 10 topproducing mines. 1.2 million tons daily (1/3 of US total) leave the field daily, a river of coal filling more than 75 trains with 150 cars each American Electric Power (AEP) has 9,100 cars and 2,480 river barges dedicated to supplying its power plants with coal

51 Biorefineries are geographically confined BioRefinery Oil refinery 51 MIT

52 S S S D=60 miles S BR S S S S

53 Economics

54 Per Barrel Cost $200 Oil Equivalent Product Prices $180 $160 $140 $120 $100 $80 $60 $40 $20 $0 - $20 CO2 cost (ignoring indirect CO2 consequences) Additional Transportation Cost Capital Cost Carbon Storage Cost Non- Feedstock Oper Cst Feedstock Cost

55 Per Barrel Cost $200 Oil Equivalent Product Prices $180 $160 $140 $120 $100 $80 $60 $40 $20 $0 - $20 - $40 - $60 CO2 cost (ignoring indirect CO2 consequences) Addi?onal Transporta?on Cost Capital Cost Carbon Storage Cost Non - Feedstock Oper Cst Feedstock Cost Cost of fuels produced from biomass (B), coal (C), or combined coal and biomass (CB) using biochemical conversion (that is corn ethanol or cellulosic ethanol) or thermochemical conversion via Fischer-Tropsch (FT) or MTG with a carbon tax of $50 per tonne CO 2 added. For thermochemical conversion, FT and MTG with or without carbon capture and sequestration (CCS)