challenges in renewable biofuel productionilp.mit.edu/images/conferences/2012/euro/23 -...

Greg Stephanopoulos MIT-Europe Energy Conference March 28, 29, 2012

2012 MIT-Europe Energy Conference

Rome

March 28-29, 2012

Challenges in Renewable Biofuel Production

Gregory Stephanopoulos MIT


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)


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


Difference between Ethanol and all the others

We can make ethanol


Bio-fuels: Primarily a feedstock story

Produced either from

•  Biomass, or, •  Any feedstock by biological methods


Summary of the state-of-the-art in biofuel development

(in 4 slides)


1. Sugar platform

Starches (Corn) Sugarcane

Hydrolysates of plentiful biomass-algae

Sugars Ethanol

Advanced biofuels

Easy conversion

Biomass deconstruction still challenging

Straightforward with yeast

Requires Metabolic Engineering


Plentiful Biomass?


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 76 112 Wheat and grass straw 15 18 Hay 15 18 Total cropland biomass 106 148 Dedicated biofuel crops 102 164 Woody biomass 110 137 Paper and paperboard 10 20 Animal manure 6 12 Municipal solid waste 90 120 TOTAL 424 601


Potential of biofuels (USA)

  70-100 gallons ethanol/dry ton of biomass   42-60 B gallons Ethanol/year or 28-40 B gallons of gasoline equivalent 20-30% of gasoline used

  Potential is greater when advanced biofuels are produced such as biobutanol or biodielsel

(1 ton of ethanol = 333 gallons, or 1 Gallon = 3 kgs, or 1 B Gallons = 3 M tons)


Sophisticated pathway and microbe engineering is required to create biocatalysts for converting

sugars to advanced biofuels

Coupled with

Advanced bioprocessing (isobutanol)


Pentanol Synthesis

12

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

Greg Stephanopoulos MIT-Europe Energy Conference March 28, 29, 2012 13

Thiolase

Dehydrogenase &

Dehydratase Mutase Reductase

Biofuels toolkit


Biofuels toolkit


Advanced metabolic engineering

Allows biosynthesis in microbes of almost any fuel or chemical,

natural or not


Cells: Little chemical factories with thousands of

chemical compounds interconverted

through thousands of chemical reactions

Main substrate: Sugars

Products: Virtually

infinite


Redirecting Carbon Flux

Rxn

1

Rxn

3

Rxn

2

Rxn

5

Rxn

4

Rxn

6

Pentanol

Substrates ?P 2 P 4

P 4

18

CoA activator

CoA remover

HPLC analysis


2. Biofuel production by direct photosynthesis

Algae

Sun

Biomass

Oil-alkane production

Other biofuels (ethanol)

Productivities are high but cultures very dilute

Key challenge: Cost-effective dewatering

Just growth

Metabolic Engineering; Secretion?

Oil recovery


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


3. Biodiesel

Oils Biodiesel (FAME)

Simple trans-esterification reaction Key issues: Feedstock cost and availability


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)


Wild type

Recombinant Some results on recombinant oil producing microbe

Total sugar consumed: 312 g/L Total oil produced: 80g/L in 72 hours Yield: 29.4% Theoretical Maximum Yield: 31%

0

10

20

30

40

50

60

70

80

90

0 24 48 72

FAM

E (g

/l)

Lipid production

Patent pending


A tripod of feedstock and products

Feedstock: Glucose/sugar

(1 kg)

Product: Ethanol

(~0.51 kg)

Product: Fats/Oils (0.31 kg)

Amounts of two products are energetically equivalent (possible due to the almost theoretical yield of our microbe)


Electrofuels

(They can increase the yield of solar energy conversion by an order of magnitude relatively

to photosynthetic systems)


The “Electrofuels” FOA was released in Dec. 2009 in response to a need for more efficient biofuel production technologies

27

Photosynthesis

Biomass

EtOH, Advanced biofuels

Algae

Pyrolysis oils

Biodiesel, Advanced biofuels

Electrons/ Reducing equivalents

Syngas, CH3OH, CH4,

Advanced fuels?

Chemical Catalysis Biological

Catalysis

Advanced Fuels

Electrofuels


Bio-GTL

Goal: Produce an infrastructure compatible fuel (biodiesel) from CO2 and CO/H2 Asset: Oleaginous microbe with extremely high yields, productivities, and titers Strategy: Fix CO2 with CO/H2 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

Ana

erob

ic C

O2

redu

ctio

n

H2OSplit

O2

H2

Aerobic oil production from CO2product

OIL

Product of CO2 fixation

NewCO2Recycled CO2

Ana

erob

ic C

O2

redu

ctio

n

H2OSplit

O2

H2


OIL

Product of CO2 fixation

NewCO2Recycled CO2

Ana

erob

ic C

O2

redu

ctio

nA

naer

obic

CO

2 re

duct

ion

H2OSplit

O2

H2

H2OSplitH2OSplit

O2

H2


OIL


OIL

Product of CO2 fixationProduct of CO2 fixation

NewCO2Recycled CO2

NewCO2Recycled CO2


Supporting Evidence

Growth and acetate production of Acetobacterium woodii on fructose and H2/CO2

 Preliminary Calculations:  Acetate Productivity: 2.4 g/

L/day (0.1 g/L/h)  0.274 g oil/g acetate  3.33 Kg OIL/Gal  ~170 Million gals of

fermentor capacity required for a 50Mgal/year oil plant

 O.D. 25-30x lower of a typical EtOH fermentation

 Specific rate g/g/hour comparable to ethanol


Main Challenges

  Main Challenge 1: Improve oil production from acetate: 20-30 g/L at yields greater than 80% of theoretical maximum and productivities of 0.6-1.0 g/L/h

  Main Challenge 2: Increase Volumetric Productivity of acetate production by ~ 15 fold


4. Bio-GTL

Natural gas Steel mills

Gasification of biomass, MSW, coal

SynGas

Ethanol

Advanced biofuels

Expensive gasifiers

Clostridia (Koskata, AlzaTech)

Acetate

Acetogens (Moorella)

OIL

via Metabolic Engineering


CO2

Acetyl-CoA Metabolic pathway

2e -

2e - 2e -

2H+ + 2e -

Acetyl CoA

Acetic Acid Ethanol

2e -

2e -

Met

hyl B

ranc

h

Car

bony

l Bra

nch

Acetyl - PO32-

ATP

Acetaldehyde

Hydrogenase

CODH 2e -

Acetyl-CoA Synthase

ATP

CO2

CO

H2

2e -

Isobutanol and other biofuels


Electron production

2 CO2 + 8 e- C2H4O2

Acetyl-CoA pathway

H2 2 H+ + 2 e-1

CO + H2O CO2 + 2 H+ + 2 e-1

hydrogenase

CODH

If electrons from H2

2 CO2 + 4 H2 C2H4O2 + 2 H2O If electrons from CO

4 CO + 2 H2O C2H4O2 + 2 CO2

4 moles needed


Gas fermentation challenge: solubility

Species C* (mM) CO2 48 CO 1.2 H2 0.83

@T=37 0C, P=1 atm.

Strategies: 1.  Closed bioreactor: High pressure 2.  Continuous-gas bioreactor: High mass transfer rate


Summary of kLa

Reactor Diffuser Agitation (rmp) kLa (1/hr) Stirred tube 100 1.74

Column tube NA 13.2 Column Micro bubble NA 25.8


0

5

10

15

20

25

30

0 50 100 150 200 250 300

Tota

l Car

bon

(g/l)

Time (hr)

Carbon utilized-exp 2 CO availability-exp 2

CO2 availability

Carbon utilization: Experiment 1

Utilization = 0.5×cell mass + 0.4×Cacetate

(g/l)

Availability of Gas = 12×kLa×C* (g/l/hr)

)( *tLA CCakN −=


0

5

10

15

20

25

30

0 50 100 150 200 250 300

Tota

l Car

bon

(g/l)

Time (hr)

Carbon utilized-exp 1 Carbon utilized-exp 2 CO availability-exp 1 CO availability-exp 2 CO2 availability

Carbon utilization: Experiments 2,3

  Gas fermentation is limited by CO availability 4 CO + 2 H2O C2H4O2 + 2 CO2


Experimental summary-Acetogens

Feedstock Acetate (g/l) Productivity (g/l-hr) CO2, CO, H2 25 0.13

CO2, CO 29 0.18 CO 30 0.40

Glucose, Syngas 21 0.39 Glucose, CO2 26 0.42

Electron donors: H2, CO, glucose Electron acceptor: CO2


The future of biofuels: Take away points

1.  Corn ethanol will max out at ~15B Gallons/year 2.  Biomass supply: Sufficient for 25-40 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


The future of biofuels: Take away points (cont’d)

7.  Drop-in biofuels: Unnecessary. Aim for maximum cost-effectiveness

8.  Algae: Were promoted on the basis of productivity and not-land 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


The end

Questions?


•  Co-products   Marketing such compounds

as, higher-priced, chemicals

u Summary: Bio-GTL technology


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

What is the likelihood that one of the advanced biofuels will compete

successfully with ethanol?


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 ~ $1.20-1.40 •  Hence, biodiesel can be produced from sugars at an estimated total cost of $1.80-2.00 •  Probably less with other feedstocks that have potential for drastically lower cost


0

50

100

150

200

250

300

0 10 20 30 40 50 60 70 80 90 100

OD

Hours

2L fermenter

YL-‐Eng-‐OD

YL-‐Wild-‐OD


14

26

105

123

0

20

40

60

80

100

120

140

CB+Hemo+Glut1 D9+CB+Hemo+Glut1

TAG/

Sugar g

/l

Mutant strains

2L bioreactor with C5 Hz with 200g/l sugars

TAG

Sugar consumed

Mutant1 Mutant2


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

Mutant 2 Mutant 1 Mutant 3

41

155


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 0.75-0.85 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


Where is this biomass?


•  1.1 Billion tons mined per year •  Gillette Coal field (Wyoming): 80 miles strip with 10 top-producing 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

Coal does not come easy


Biorefineries are geographically confined

51 51 MIT

Oil refinery BioRefinery


BR D=60 miles

S

S

S

S

S

S

S

S


Economics


-‐$20

$0

$20

$40

$60

$80

$100

$120

$140

$160

$180

$200Per Barrel Cost Oil Equivalent Product Prices

CO2 cost (ignoring indirect CO2 consequences) Carbon Storage CostAdditional Transportation Cost Non-‐Feedstock Oper CstCapital Cost Feedstock Cost


-‐ $60 -‐ $40 -‐ $20 $0

$20 $40 $60 $80

$100 $120 $140 $160 $180 $200 Per Barrel Cost Oil Equivalent Product Prices

CO2 cost (ignoring indirect CO2 consequences) Carbon Storage Cost Addi?onal Transporta?on Cost Non -‐ Feedstock Oper Cst Capital Cost 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 CO2 added. For

thermochemical conversion, FT and MTG with or without carbon capture and sequestration (CCS)

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