Citrus-Based BiorefineryCitrus-Based Biorefinery- Opportunities and Challenges -- Opportunities and Challenges -

Patrick L. MillsPatrick L. Mills Dept of Chemical & Natural Gas Engineering Dept of Chemical & Natural Gas Engineering

Texas A&M University-KingsvilleTexas A&M University-Kingsville Kingsville, TX 78363 Kingsville, TX 78363

Patrick.Mills@tamuk.eduPatrick.Mills@tamuk.edu

OH

CREL Annual Meeting – Washington University in St. LouisCREL Annual Meeting – Washington University in St. LouisEnergy: From Molecular Transformations to SystemsEnergy: From Molecular Transformations to Systems

October 25, 2006October 25, 2006

www.praj.netwww.ars.usda.gov

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GRADUATED

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GRADUATED

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REQUI REMENTS

THEN WE’LL REWRI TEOUR DEPARTMENTMI SSI ON STATEMENTTO MAKE I T FI T BETTER

GRADUATED

FI RST, WE’LL REDUCEOUR DEPARTMENTEXPENSES BY LOWER-I NG OUR GRADUATI ON

REQUI REMENTS

THEN WE’LL REWRI TEOUR DEPARTMENTMI SSI ON STATEMENTTO MAKE I T FI T BETTER

GRADUATED

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The New Departmental PlanThe New Departmental Plan

Starting ReferencesStarting References

2. R. J. Braddock, Handbook of Citrus By-Products & Processing Technology,Wiley-Interscience: New York, ISBN 0471190241, 247 pp, 1999.

4. Dan A. Kimball, Citrus Processing: A Complete Guide, 2nd Edition,Chapman & Hall Food Science Series, Aspen Publishers, Gaithersburg, MDISBN 0834212587, 450 pp, 1999.

5. T. R. Graumlich, “Potential fermentation products from citrus processingwastes,” Food Technology, 94-97, Dec 1983.

6. W. Q. Hull, C. W. Lindsay, & W. E. Baier, “Chemicals from oranges,”Ind. Engng. Chem., Vol. 45, No. 5, 876-890, May 1953.

3. R. J. Braddock, “Importance of by-products to citrus juice processing,”Fruit Processing, 5, pp 310-313 (2004).

1. B. Kamm, P. R. Gruber, & M. Kamm (editors), Biorefineries – IndustrialProcesses & Products: Status Quo & Future Directions,John Wiley: New York, ISBN 3527310274, 964 pp, April 2006.

Morphology of Citrus FruitMorphology of Citrus Fruit

zest

Pericarpor rind

Orange Citrussegment

wall

Mesocarp orpulp

www.infovisual.info

• 40 to 65 wt % juice• 35 to 60 wt % waste

• Lipids - oleic, linoleic, linolenic, palmitic, stearic acids; glycerol & physterol

• Sugars - glucose, fructose, sucrose, galactose, xylose, rabinose, ….)

• Acids - citric, malic, tartaric, benzoic, oxalic, succinic

• Insoluble carbohydrates – cellulose, pectin

• Flavonoids, peel oil, pigments, vitamins, minerals, …

Nutrient Composition of Citrus By-ProductsNutrient Composition of Citrus By-Products

Total World Annual Citrus Production*Total World Annual Citrus Production*

70 to 105 million tons/yr 70 to 105 million tons/yr 2000–2003 (avg’d) 2000–2003 (avg’d)

*USDA/FAS, 2003 Horticultural & Tropical Products Div.,Wash.,DC

Sweet Orange

68%

Minor genuses

3%

Tangerine18%

Lemon6%

Grapefruit5%

- Sour orange- Shaddock- Citron- Lime

USA21%

Brazil24%Med

24%

ROW31%

C. Reticulata

C. Sinensis

C. LimonC. Paradisi

C. QuanantiumC. GrandisC. MedicaC. Aurantifolia

Example: Florida Citrus Production*Example: Florida Citrus Production*

*USDOE, Office of Energy Efficiency & Renewable Energy

MM = 1 x 106

Property AmountCitrus Trees, MM 103Acreage 800,000USA Production 80%Citrus Boxes, MM 287On-Tree Value $1 MMMTotal Industry Value $ 9 MMMWet Waste, MM tons 5Dry Waste, MM tons 1.25EtOH Potential, MM gals 120

Added ValueFrom JuiceBy-Products

90 lbs/box

Citrus Juice Process & Material BalanceCitrus Juice Process & Material BalanceFresh Citrus Fruit

3000 b/hr 123,000 kg/hr

Juice extractors

Wet Peel54,600 kg/hr 82% H2O

Dryer Feed25,600 kg/hr 61% H2O

Press Cake19,000 kg/hr 65% H2O

Hammermill

Reaction Time

Presses

Dryer 14,500 kg/hr

Press Liquid35,600 kg/hr 9o Brix

Citrus Juice

Waste Heat Evap30,000 kg/hr

Oil Mill / Plant Waste

Molasses6400 kg/hr 9o Brix

33.4 %

Pellets11,000 kg/h 10% H2O

d-Limonene140 kg/hr

Molasses4400 kg/hr 72o Brix

66.6 %

(Soluble Fraction)(Soluble Fraction)

(Insoluble Fraction)(Insoluble Fraction)

Process Flow for Citrus By-ProductsProcess Flow for Citrus By-Products

Fresh Citrus Fruit Residue(Ground or Chopped)

Citrus SeedsDried Citrus Pulp

with Liquor

Press LiquorPressed Fresh

Pulp

Citrus Molasses

Citrus SeedMeal

Citrus OilsDried Citrus Pulp(w/o Molasses)

Dried CitrusMeal

Pressure withAdded Ca(OH)2

Sold as Molasses

Dried Citrus Pulp(with Molasses)

Pelleted & AddedBack to Pulp

Pressure Sieved

Dehydration Dehydration

Dehydrated without pressing

Ca(OH)2 added

Addition

Bampidis & Robinson, Animal Feed Sci. Tech. 128 (2006)

Distribution of Citrus By-ProductsDistribution of Citrus By-Products

9.80

4.90

3.43 3.19

0.74 0.74 0.49

0

2

4

6

8

10

Wt % ofBy-Product

(Orange Basis)

Basis: Basis: OrangesOranges = 40.8 kg/box; = 40.8 kg/box; Juice Yield Juice Yield ca.ca. 55%55%

Distribution of Orange Juice By-ProductsDistribution of Orange Juice By-Products

Basis: 2005 – 2006 USA Production of 695,275 MTBasis: 2005 – 2006 USA Production of 695,275 MT

Source: www.fas.usda.gov

Flavonoids2%

Pulpwash soluble solids

3%

Pectin (150 grade)

14%

Molasses (72 °Brix)15%

Peel dry pellets (10% H2O)

42%

Essential oil and d-limonene

3%

Frozen pulp21%

Pectin & Pectic AcidPectin & Pectic Acid

Pectic Acid (D-Polygalacturonic acid)

Pectin Molecule

Recovery of Pectin from Citrus PeelRecovery of Pectin from Citrus Peel

• Pectin (a polysaccharide) - white, spongy inner part of the peelPectin (a polysaccharide) - white, spongy inner part of the peel

• Significant yield loss & waste generation with conventional hydrolysis Significant yield loss & waste generation with conventional hydrolysis

BackgroundBackground

OpportunityOpportunity• Significant growth in use of low-methodoxylSignificant growth in use of low-methodoxyl (LM) pectin as a pectin as a

- Thickening or gelling agent- Thickening or gelling agent

- In formulated food applications (yogurt, milk, desserts, etc...)- In formulated food applications (yogurt, milk, desserts, etc...)

• Method for extraction & conversion of high-methodoxyl (HM) pectinMethod for extraction & conversion of high-methodoxyl (HM) pectinfrom citrus peels with high efficeincyfrom citrus peels with high efficeincy

• New enzyme or catalysts for rapid conversion of HM to LM pectinNew enzyme or catalysts for rapid conversion of HM to LM pectin

• Efficient methods for purification and formulationEfficient methods for purification and formulation

NeedsNeeds

Citrus Peel Waste as a Bio FeedstockCitrus Peel Waste as a Bio Feedstock

• Represents ca. 40 to 50 % of citrus fruitRepresents ca. 40 to 50 % of citrus fruit

• Dried pellets used as cattle feed supplementDried pellets used as cattle feed supplement

• Second to corn as a source of feed nutrientsSecond to corn as a source of feed nutrients

• CaO added - neutralize & de-esterify pectinCaO added - neutralize & de-esterify pectin

• Diffusion controlled process w/molassesDiffusion controlled process w/molasses

• COM can exceed cattle feed selling priceCOM can exceed cattle feed selling price

• Contains Contains solublesoluble & & insolubleinsoluble carbohydrates carbohydrates ((glucose, fructose, sucroseglucose, fructose, sucrose, , pectin, cellulose,pectin, cellulose, hemicelluloseshemicelluloses w/ galacturonic acid, glucose, w/ galacturonic acid, glucose, arabinose, xylose, … as monomeric units)arabinose, xylose, … as monomeric units)

Composition of Citrus JuiceComposition of Citrus JuiceProcessing Wastes (Wet Processing Wastes (Wet vsvs Dry Material) Dry Material)

0

10

20

30

40

50

60

70

80

90

Water TotalSolids

Solublesugar

AlcoholInsoluble

Solids(AIS)

CrudeFiber

Pectin CrudeProtein

Fat (Ether

extract)

Ash

Wt%

Composition at Minimum Water (W%)

Composition at Maximum Water (W%)

Dry Material

• Higher polysaccharide concentration

• Greater potential yield of sugars

• Higher energy consumption vs wet

• Higher pectin vs wet material0

10

20

30

40

50

60

70

80

90

Solublesugar

AlcoholInsoluble

Solids(AIS)

CrudeFiber

Pectin CrudeProtein

Fat (Etherextract)

Ash

Wt%

Composition at minimum AIS%

Composition at maximum AIS%

Wet Material

• Lower sugar content vs dry material

• Lower yield of sugars

• Lower energy consumption

• Hydrolysis of polysaccharides req’d

Composition of Alcohol Insoluble SolidsComposition of Alcohol Insoluble Solids (Cell Wall Fraction of Orange Peel)*(Cell Wall Fraction of Orange Peel)*

0

5

10

15

20

25

30

Wt %

Not Useful forEtOH Production

Grohmann & Bothast, ACS Symp Ser. 566 (1994)

Raw Materials forEtOH Production

• Fructose & glucose present in nearly equimolar amountsFructose & glucose present in nearly equimolar amounts• No starch is present, unlike other Ag residsNo starch is present, unlike other Ag resids• Some organic acids, Some organic acids, e.ge.g., galacturonic acid., galacturonic acid

D-Galacturonic Acid D-Galacturonic Acid StructureStructure

- Formed by the hydrolysis of - Formed by the hydrolysis of

pectinpectin

- Can be converted to d-glucose- Can be converted to d-glucose

Conversion of Orange Total Peel Solidsto Monomeric Sugars

- Comparison of Various Treatments-

Conversion of total peel solids to monomeric sugars by enzymatic and combined acid and enzymatic treatments. Left bar (Unt) of each pair represents a mean of results obtained by enzymatic treatment alone, without acid treatment. The right bar (Tr) of each pair represents the mean of results obtained by sequential acid and enzymatic treatment. The symbols above each pair of bars represent the enzymes (or combination of enzymes) used in the enzymatic part of the treatment (C=cellulase; P=pectinase; -glucosidase). The last pair of bars, labeled I"PCG, represents results of a treatment with a mixture of pectinase, cellulase and ~-glucosidase in excess. The individual sugars released are marked on the right side of the graph (Ara=arabinose; Fru=fructose; Gal=galactose; Glc=glucose; G.A=galacturonic acid; Xyl=xylose). Grohmann, K.; Cameron, R.G;. Buslig, B.S Bioresource Technology 54 (1995) 129-141

C CG P PC PCG PCG

Su

cro

se

Glu

cos

eF

ruc

tos

eG

alac

tose

Ara

bin

ose

Xyl

ose

Rh

am

ose

Gal

act.

aci

dT

ota

l S

ug

ars

Inso

l. R

esid

.U

nk

no

wn

Aqueous Extract

Insol. Solids (Acid Hydrolyzed)

Insol. Solids (Enzy. Hydrolyzed)

Enzy. Hydrolysate of Peel

0

20

40

60

80

wt %

Products from Various Solubilization MethodsProducts from Various Solubilization Methods

Enzymatic Hydrolysis of Orange Enzymatic Hydrolysis of Orange PeelPeel

Conversion of total peel solids to reducing sugars during enzymatic hydrolysis of untreated orange peel ( ...... ) and peel pretreated with 0-06% sulfuric acid at pH=2.0 at 100, 120 and 140°C for 10 min, respectively. Treatments: a No acid pretreatment;---<> . pH=2-0, 100°C, 10 min; ---o . . . . pH=2.0, 120°C, 10 min; - - - + . . . . pH=2.0, 140°C, 10 min.. Grohmann, K.; Cameron, R.G;. Buslig, B.S Bioresource Technology 54 (1995) 129-141

Enzymatic w/o acid pretreatment

Enzymatic w/diluteacid pretreatment

Effect of Particle Size onEffect of Particle Size onEnzymatic Hydrolysis of CelluloseEnzymatic Hydrolysis of Cellulose

Comparison of shake-flask and attrition methods for enzymatic hydrolysis of Whatman CF-11 cellulose. ( ) Unmilled control, () ball milled, () 60 g of glass beads, ( ) 136 g of stainless-steel beads, all with a shaker speed of 200 opm. () Attrition at 200 rpm. Cellulase complex PP 158: 1 IU/mL and 2% substrate. Neilson M. J., Kelsey, R. G ., and Shafizadhe F (1982). Biotechnology and Bioengineering, Vol. XXIV, pp. 293-304

w/o milling

conv. ball milling

Glass beads

SS beads

Attrition mill

Novel Hydrolysis Schemes of Citrus PeelNovel Hydrolysis Schemes of Citrus Peel

• Peel celluose & hemi-cellulose contain value-added glucose, sucrose,..Peel celluose & hemi-cellulose contain value-added glucose, sucrose,..

• Existing hydrolysis methods are slow (on the order of days)Existing hydrolysis methods are slow (on the order of days)

• Lack of basic understanding of hydrolysis kinetic-transport effects Lack of basic understanding of hydrolysis kinetic-transport effects

BackgroundBackground

OpportunityOpportunity

• Develop methods and process with significantly higher Develop methods and process with significantly higher conversion rates and selectivities to monomeric sugarsconversion rates and selectivities to monomeric sugars

• Novel enzymes, catalysts, and reactor systemsNovel enzymes, catalysts, and reactor systems

• Basic data on the reaction mechanism & kinetic-transport effects Basic data on the reaction mechanism & kinetic-transport effects

• Mathematical models for kinetics, transport, & reactor systems Mathematical models for kinetics, transport, & reactor systems

NeedsNeeds

Production of Orange Juice By-ProductsProduction of Orange Juice By-Products

Basis: 2005 – 2006 USA Production of 695,275 MTBasis: 2005 – 2006 USA Production of 695,275 MT

Source: www.fas.usda.gov

123.9

43.4

9.3 9.3

40.3

62.0

6.2

294.3

0

50

100

150

200

250

300

Dry pellets(10% H2O)

Molasses(72 °Brix)

Essentialoil and d-limonene

Pulpwashsolublesolids

Pectin (150grade)

Frozenpulp

Flavonoids Total

1 X

103 M

etr

ic T

on

s

Catalytic Oxidation of LimoneneCatalytic Oxidation of Limonene

trans-carveol

OAc

-terpinyl acetateR-Limonene

OH

+ O2

PdCl2 / CuCl2

HOAc

15 hr, pH = 6

or

R-Limonene

+ O2

PdCl2 / CuCl2

tert - BuOH

tert – BuOOH (aq.)

OOt-Bu

OOt-Bu

tert-butyl peroxide derivatives

+

w/o LiCl with LiCl

Oxdn of Limonene - Product DistributionOxdn of Limonene - Product Distribution

OAc OAc

1 2 3

O OH

4 5 6

OH

OAc

a. Conventional Wacker

OH OH O OH

OH

CHO

OOt-Bu

OOt-Bu

OOt-Bu

5 7 4 8 9

10 11 12 13 14

OH

b. Wacker with t-BuOH & t-BuOOH

Functionalized Derivatives of D-LimoneneFunctionalized Derivatives of D-Limonene

• Limonene & other mono-terpenes are recovered from citrus peel oilLimonene & other mono-terpenes are recovered from citrus peel oil• Derivatives (alcohols, aldehydes, ketones, allylic ethers, carboxylicDerivatives (alcohols, aldehydes, ketones, allylic ethers, carboxylic

acid esters, epoxides…) are useful in pharma, perfumery, flavors acid esters, epoxides…) are useful in pharma, perfumery, flavors

BackgroundBackground

OpportunityOpportunity

• Limited literature exists on application to natural products Limited literature exists on application to natural products

• Synthesis of new molecules, specialty polymers, & materialsSynthesis of new molecules, specialty polymers, & materials

• New organometallic catalysts for mono-terpene functionalizationNew organometallic catalysts for mono-terpene functionalization

• Fundamental studies on kinetics, mechanisms, multifunctional reactors Fundamental studies on kinetics, mechanisms, multifunctional reactors

• Novel multiphase microreactor system designs & mini-plants Novel multiphase microreactor system designs & mini-plants

NeedsNeeds

Example of a Flavonoid - DiosmetinExample of a Flavonoid - Diosmetin

• A human CYP1A enzyme activity-inhibiting natural flavonoid.A human CYP1A enzyme activity-inhibiting natural flavonoid. • Diosmetin has antimutagenic and anti-allergic behavior.Diosmetin has antimutagenic and anti-allergic behavior.

Flavones & FlavonoidsFlavones & Flavonoids• Naturally occurring aromatic secondary

plant metabolites

• > 4000 have been identified in plants

• Positive health benefits- antioxidants - cardioprotective- antiviral - anticarcinogenic- antiallergenic

• Amount & type depends on citrus genusand agricultural growth factors

Novel Sepn & Conversion Methods for By-ProductsNovel Sepn & Conversion Methods for By-Products

• By-products (lignin, protein, limonene..) are produced in variousBy-products (lignin, protein, limonene..) are produced in various

parts of the existing citrus process (hydrolysis, milling, etc.)parts of the existing citrus process (hydrolysis, milling, etc.)

• Some behave as enzyme inhibitors, microbiocides, contaminants,… Some behave as enzyme inhibitors, microbiocides, contaminants,…

BackgroundBackground

OpportunityOpportunity

• Develop rxn-sepn methods or processes that convert theseDevelop rxn-sepn methods or processes that convert theseto value-added products (flavors, perfumes, nutraceuticals,..)to value-added products (flavors, perfumes, nutraceuticals,..)

• New enzymes, catalysts, and/or reaction-sepn processes New enzymes, catalysts, and/or reaction-sepn processes

• Insight and new data on mechanisms & kinetic-transport effects Insight and new data on mechanisms & kinetic-transport effects

• Mathematical models for the kinetic-transport processesMathematical models for the kinetic-transport processes

NeedsNeeds

ConclusionsConclusions

• Citrus waste has potential as a biorefinery platform.Citrus waste has potential as a biorefinery platform.

• Notable differences vs corn & grain-based processes.Notable differences vs corn & grain-based processes.

• Conversion to EtOH represents one useful application.Conversion to EtOH represents one useful application.

• Specialty products would enhance economic potential.Specialty products would enhance economic potential.

• Various opportunities for novel enzymes, catalysts,Various opportunities for novel enzymes, catalysts,reactors, separations, & derivatives.reactors, separations, & derivatives.