Enzyme Catalysis for Biomass Based Diesel Fuels

Enzyme Catalysis for Biomass Based Diesel Fuels

Rachel Burton

February 20, 2014

Department of Chemical Engineering,

North Carolina State University CHE 596-16 Biodiesel Production Technology

February 20, 2014

“People don’t buy what you do, they buy why you do it.” –Simon Sinek

Outline

•  Why use an enzyma:c approach to biodiesel?

•  -‐Benefit over chemical catalysts

•  Overview of enzyma:c biodiesel •  -‐Enzymes for commercial produc:on

•  -‐Transesterifica:on

•  -‐Esterifica:on

•  Enzyme Reuse

Quick Definitions TAG = Triglycerides (fat/oil) DAG = Diglycerides FFA = Free fatty acids FAME (or ME) = Fatty Acid Methyl Esters (biodiesel made using methanol) Immobilized vs. Liquid Enzymes CALB = Candida Antarctica Lipase B Novozym 435 = CALB immobilized on a plastic support (.5mm beads) TL = Thermomyces Lanuginosa lipase

Advantages of Enzymes for Biodiesel

Sustainability Profile

•  National Research Council’s Committee on Water Implications of Biofuels Production: 1 gallon of wastewater: gallon of biodiesel produced. (Oct. 2007)

•  2007, Harding et al, LCA analysis between enzymatic & chemical catalysis for biodiesel

•  Flammable and hazardous substance exposure reduction

Improved performance linked to lower energy requirements for hea:ng in the process Terrestrial ecotoxicity levels are reduced by 40% with the removal of mineral acid from the process

Hurdles to Enzymes for Biodiesel

• 15 years of research

• Hundreds of articles

• Many different

enzymes, reaction

conditions, etc.

• Overall conclusion in

most cases – too

expense

Why Now? Chicken or the egg problem:

enzyme development vs. market development.

Confluence of events:

•  Biodiesel industry is more mature and more secure

•  Drive for lower cost feedstocks, presence of high FFA virgin oils

•  Demand for increased fuel quality •  Competition for fats/oil from

renewable diesel will push efficiency •  Industry recognition of problems

with soaps, low quality glycerin, and difficulty of acid esterification

Causes process development: •  Commercial enzyme reuse trials •  Lower cost enzyme production

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Commercial Viability!

Access to affordable feedstocks

Yellow Grease

Tallow

Soy oil

Feedstock prices rising for the 2nd time; now in accordance to petrol market

Reusability Enzymes used for biodiesel production lose

activity by:

High heat (>50C or >122F) Excess alcohol

In addition, Immobilized enzymes can lose

activity by:

Any alcohol out of phase Large excess of alcohol in phase (~5% or more)

Glycerol out of phase High shear can cause immobilized enzymes to come

off of the carrier Certain polar contaminants

Mineral acids

Temporary vs. Permanent activity loss

Temporary: physical blocking of active sites Permanent: denaturing due to excess methanol

Reusability of enzymes is the key

to commercial viability!

A brief history Early Work (1987 - 1995)

• Studied cosolvents like iso-octane, hexane, diesel fuel. • Evaluated aqueous, non aqueous, and solvent-free systems, different types of

alcohols, impact of water • Studied a wide variety of liquid enzymes

• Mike Haas, Tom Foglia, Martin Mittelbach, and many others • No real biodiesel production, so these were interesting but not practical

Resurgence of interest (1999 - 2008)

• Better immobilized enzymes • Solvent free systems, good enzyme reuse

• First large scale plant in China using cosolvents ( tert-butanol )

Current Developments • Novozymes developing enzymes, immobilization techniques, lowering costs

• Piedmont Biofuels • Transbiodiesel in Israel

• Sunho in Taiwan • Blue Sun & Viesel

• Renewed interest from universities and private biodiesel producers for lab and pilot sized reactors

Summary Articles

• Haas, 2002 (review of early literature)

• Fjerbaek, 2009

• Ranganathan, 2007

• Basic components of reviews • enzyme type

• liquid vs immobilized • support type

• reaction conditions • conversion

• number of reuses • tolerance to water, methanol

Fjerbaek et al.: Biodiesel Production Using Enzymatic Transesterification.

2009.

Cosolvents – Li (2006) Tert-butanol as

cosolvent

Advantages • Can use more excess

methanol without deactivation

• Deactivation due to glycerol (clogging) does

not occur •  Impressive enzyme reuse

Built full scale plant based on

this process in China

Disadvantages • Large amount of co-solvent required which must be removed at the end via

distillation • Still had high FFA at end of process

• Reaction rate still slow

Cosolvents – Zheng (2008) • Tert-Amyl Alcohol as cosolvent

Batch Reactions • 1.78g soybean oil

• 2 – 6ml amyl alcohol • 2% Novozym 435 (CALB) •  reaction time ~ 15 hours

• Add graph here

Excellent reuse, but same problems as Li

Watanabe and Shimada (2001, 2005)

No cosolvent Use multi-stage methanol addition

to avoid deactivation Tested batch and continuous

Advantages

• No cosolvents • Minimize methanol use

• Excellent conversion (98%+) • Good enzyme reuse

Disadvantages • Still has long reaction times • Still had high FFA at end of

process • Enzyme reuse still not

commercially viable


Packed

Bed

Reactors


Esterification – very fast!

Determined maximum methanol allowable before deactivation

• 6.3% by weight methanol

Performed Enzyme Reuse Trials • Excellent conversion (98%+)

• Good enzyme reuse

Novozymes (2009)

Longevity trials: Esterification

Reaction Conditions • 20% by volume methanol, 2 stage

reaction, 45C, • Majority of reaction finished in 60

minutes • Blended FAME, MeOH, and PFAD to

address the high melting point

Still has deactivation

Relatively large excess methanol use (~2:1)

Still high FFA content (3 – 5%) after

2nd stage

U.S. Dept. of Energy: Piedmont Biofuels – Commercial Focus

Esterification

Achieving ASTM specifications

Commercial viability (enzyme reuse)

Real World Feedstocks

• Yellow Grease (15% FFA) • Brown Grease (80%+FFA)

• Palm, soy, and others

Enzymatic approach for Waste-Water Reduction

• Began investigation of enzyme catalysis for biodiesel, 2009

• Focus on esterification first •  2010---Lab working on Pilot scale (35 gal.) •  2011/2--- Pilot moving to Commercial •  2013---on-going Commercial Integration •  Validation for multi-feedstock production scheme

• First to demonstrate enzyme biodiesel to meet full ASTM specification. • Economic analysis & Enzyme reuse

CSTR system with alcohol metering, patent pending

Enzymes For Biodiesel Production

Commercial formulations: Callera series

Commercial Build

Feed Tanks

How can you use this process? •  Enzyma:c Esterifica:on: •  A. Pretreatment for exis:ng chemical plants •  B. Full conversion-‐-‐Esterifica:on for High FFA feedstocks

•  C. Enzyma:c Polishing for TRANSESTERIFICATION followed by the enzyma:c esterifica:on PROCESS

•  -‐-‐100% enzyme-‐based process in 2 steps

Replace Sulfuric Acid Pretreatment • Esterification using Callera Ultra/L Immobilized CALB or Liquid CALB

• Replaces traditional sulfuric acid technology

• Incoming Feedstocks: 2-100% FFA • Patent Pending, continuous process

• Low temperature process

• Maintains water balance • 6-12 times less methanol than acid esterification

• No acidic methanol sidestream FAeSTER Process: Fatty Acid esterification

Feedstock Pretreatment Esterification occurs quickly within 30 minutes

Achieves acid value specification by 90 minutes

Liquid enzyme transesterification •  Heat/Circulate Feedstock (42 gallons, 40ºC) •  Initial Batches

–  1%-2% enzyme by feedstock weight –  Aqueous Phase of 20% by feedstock weight

•  40% water •  60% glycerol

•  Methanol Dosing –  1.7 molar excess of methanol to feedstock –  25% initial –  Remainder metered in over 5 hours

•  Sampling –  1, 2, 4, 6, 8, 10hr

•  FAME Phase: Bound Glycerine & FFA –  24 hr

•  Aq. Phase: Glycerol, Methanol, H2O, Enzyme –  Determine Aq. Phase Removal & Methanol Dosing –  Part II

Pilot Scale Results

Commercial scale Results

Reaction complete in 6-8 hours

In-spec Bound Glycerin 0.15% 1.5FFA%

2700 gallon reactor, coil-heated,

SS, cone-bottom, 35-40C/95-104F,

20% water/glycerol, 1.7:1 methanol:FA

Reaction monitored:

1, 2, 4, 6, 8 hrs.

NOVOZYMES PRESENTATION 2/19/14 32

Alkaline wash reduce free fatty acids and glycerides and make final biodiesel meet specifications.

The soap stock is acidified and sent back

NOVOZYMES PRESENTATION�� 2/19/14 33

0

0.5

1

1.5

2

2.5

3

Before CW AXer CW

% in FAM

E TG

DG

MG

FFA

BG = 0.17%

BG = 0.10%

The enzyme works at the oil/water interface

Mixing is important – we need a an emulsion with a large surface area between oil and glycerin/water phases


Oil/FAME

Glycerin/water

Mixing


Glycerides + MeOH glycerides/glycerin + FAME

Glycerides + H2O glycerides/glycerin + FFA

FFA + MeOH FAME + H2O

Driving process by

increasing Methanol and

decreasing Glycerol and Water

Reaction at interface

Enzyme process works well with any content of free fatty acids

Affect of Water:

Too much water leads to reac:on with FAME back to FFA.

Too li\le water leads to enzyme inac:vity.

Affect of Methanol: Excess methanol inhibits the enzyme. Too li\le methanol slows reac:on.

Loss of Active Enzyme:

Loss of Enzyme = slower reac:on rate.

Balancing Act

–  2010: ASTM D6751 achieved using only

immobilized enzymes

2011: ASTM D6751 achieved using Liquid

TL & CALB

2012 + : Commercial Scale

Integration

100% Enzyme-Based Fuel meets ASTM D6751

Glycerol from Enzymatic Process

•  High purity Glycerol 99.6%

•  Economic Impact to the producer:

•  40-50 cents/lb. • 

Chemical glycerol vs. enzymatic glycerol

Chemical FAME/glycerol vs. FAME/enzymatic glycerol YELLOW GREASE FEEDSTOCK

2/19/14 39

Tsinghua China – Hunan plant Lipase-mediated industrial scale production of biodiesel (20,000t/y) put into operation Dec 8, 2006. Initially in a process with t-butanol; Now restarting in solvent free process


Final product

Blue Sun - USA. 3 enzyme reactors of 300 m3 each

Started early 2013


Viesel Biofuels – Florida USA

Summary Variables

Methanol use (minimize) Cosolvents (minimize)

Reaction time (minimize) Presence of water (minimize)

Ester conversion per minute (minimize) Final ester conversion (minimum 98% esters)

Final FFA content (maximum 0.25% FFA) Temperature (35 – 50)

System design

PBR CSTR

Continuous Batch

System robustness

multi-feedstock tolerance to impurities

Enzymes as a biodiesel catalyst are extremely well studied

but also very complex.

Still, probably worth the effort...

Type of Enzyme Candida antarctica lipase B

Thermomyces lanuginosa Pseudomonas cepacia

Rhizomucor miehei

Carrier Polypropylene

Polyethylene Activated Carbon

Silica

Form of enzyme Liquid

Immobilized

Lower Energy Use

No Soap Formation

High Quality Glycerin

Non-Toxic Low Methanol Use

Scale Neutral More Complete

Separations Esterify and Transesterify

A more competitive biodiesel industry