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  • 90% of all citrus produced in Florida is processed into juice and other products

  • Only about 1/2 of a citrus fruit is juice with the remainder becoming waste
  • n An average of 5 million tons (wet) of citrus processing residues were generated annually from over 11 million tons of annual citrus production in Florida between 1993-2004 with even higher amounts produced in Brazil

 

  • Since 2004, the citrus residue production dropped to about 3.0- 3.5 million tons (wet) annually due to hurricane and pest damage, but the Florida industry is recovering

 

  • Current practice to handle the waste is to dry and market dried citrus pulp pellets (CPP) as a cattle feed

 

  • Citrus processing residue is rich in simple and complex carbohydrates making it a good cattle feed, but it is low in protein

 

  • Until 2007, the value of CPP ($40 - $80/ ton) has been about equal or less than the production costs ($60 - $100/ton)

 

  • The increase in the price of corn along with other factors have now increased the value of CPP to approximately $170/ton

Citrus Pulp Pellets

A. large market, cheap storage and transportation
 

B. Low price ( 2-10¢/lb )
 

C. Limited or no diversification into other products and markets

Composition of Citrus Processing Residue
Approximately:   75-80%              Water
                           0.5-1.4%              Citrus oil
                             20-25%              Dry matter
 
Dry matter contains:
 
23 - 28% simple sugars
  8 - 10% cellulose
  8 - 12% hemi cellulose
 
    20   % pectin
 
    20   % mix of flavonoids
limonoids 
organic acids
protein
minerals

8-10 % cutin, waxes

 

 
   Why Ethanol?
  • Ethanol is one of the few products which can consume the large volume of CPW

  • Market development is not required

  • The value of ethanol exceeds the value of CPP even on sugar basis

  • Fuel ethanol price is $2.20-2.80/gal( i.e. 33-43¢/lb or 17-21¢/lb sugar)

  • Potable ethanol ≥ $3.80/gal

  • No fuel ethanol produced in Florida, yet

 

 

 

 

 

 

Challenges

  • Processing of CPW particles at high concentration of solids - Heat transfer - Mixing and conveying - Distillation

  • Limonene Removal

  • Sterilization

  • Enzyme cost

  • Energy (steam) consumption

  • Cattle feed acceptance

  Accomplishments

  • Pilot scale plant consuming up to 1-2 ton CPW/hr has been developed and operated for two seasons.

  • Three US Patents have been awarded for the innovative process and it’s parts:
    US Patent 7,721,980 B1, May 25,2010 US Patent 7,879,379 B1, Feb. 1 ,2011 US Patent, awarded Oct. 2012, in press

  • Limonene removal to ≤ 0.05% (≥ 95% removal) has been achieved.

  • Sterilized and disintegrated CPW mush has been prepared, hydrolyzed and fermented in simultaneous saccharification and fermentation process.

  • Enzyme cost has been lowered by more than an order of magnitude to about 50¢/gal ethanol.

  • Novel distillation column for stripping of ethanol from viscous (6,000-30,000 cP), fermented CPW has been developed.

  • Stripping of ethanol from CPW and it’s rectification to 95% concentration has been developed at the pilot scale level. Cars were driven using ethanol from CPW as a fuel.

  • Blending of simulated stillage with CPW and it’s incorporation into feed mill operation has been demonstrated.

  • Pretreated CPW and stillage were fed to cattle with excellent acceptance and no ill effects.

  • CPW from oranges, grapefruit and tangerines has been successfully processed


Production Costs of Citrus Ethanol  1,2

 
Cost Per Gallon
Citrus Peel ($0/ton)
$ 0.00
Chemicals, Enzymes  
$ 0.835

Utilities (steam,el. )

$ 0.628

Labor, Supplies & Overhead Expense



$ 0.156

Capital Depreciation

$ 0.301

 Drying of Residues  
  $ 1.40
Total Cost
1 Includes limonene
   costs
$ 3.32
Products
Value
Ethanol (1 gallon)
$ 2.25
Limonene (1.7-3.4 lb @$2.00/lb)
$ 3.40-6.80
Dried Pulp Pellet
(38 lb @$150/ dry ton)
$ 2.85
 
 
 
   
Total Value
2Size: 1,792 tons of fruit/day
$ 8.50-11.90

 

    Effect of Plant Size

Cost comparison

Citrus Pulp Pellets       Ethanol & Co-products
 

Cost/dry ton
CPW $ 0
Pressing & Drying $100
Income/dry ton
CPP $170
Limonene $ 30

Total $ 200

Net Income/dry ton
$ 100  
Cost/dry ton
CPW $ 0
Total Prod. Costs $ 116
Income/dry ton
CPP
$ 112
Limonene (@ $2/lb) $ 120-260
Ethanol (@ $2.25/gal) $ 79-101
Total $ 311-473

Net income/dry ton
$ 195-357
 

Alternative Ethanol Process

                        3-6 lb limonene

                 

Potential Products from CPW

Value Added Co-products

  • Higher value than cattle feed; $0.30-10.00/lb

  • Possible elimination of drying of stillage

  • Positive economic impact

  • In some cases products and markets need to be developed

Accomplishments

  • Recombinant bacteria for fermentation of residual C5 and C6 sugars are being developed in collaboration with Prof L. Ingram at Univ. of Florida. A 50% increase in ethanol yield, concentration and income from ethanol is possible and waste treatment will be simplified.

  • A new method for preparation and recovery of pectic fragments has been developed. The fragments have a value as ion exchangers and precipitants for heavy metal ions.
     

 

Conclusions

  • CPW is a suitable raw material for the production of fuel or potable grade ethanol

  • Coproduction of ethanol, limonene and cattle feed is economically attractive at current prices and relatively small (0.2-1.0 x 106 gal ethanol/season) plant sizes

  • Significant decrease in VOC emissions is achievable through better limonene recovery

  • Development of value added co-products from stillage provides additional opportunities
     

 

GOING FORWARD

  • Scale up to a commercial level

  • Formation of strategic partnerships with citrus processors and ethanol producers or chemical companies

  • Energy (steam) savings through integration of processing steps

  • Increase in ethanol yield and concentration by application of recombinant microorganisms

  • Extension of the ethanol production season by the utilization of sweet sorghum juice

  • Development of additional co-products

  • The process may be suitable for other pectin rich residues, such as sugar beet pulp or apple pumice

Thanks

  • USDA/ARS - CRADA Partner

  • Florida Department of Citrus

  • Peace River Citrus

  • Blue Lake Citrus

  • USDA and US DOE – 2 research grants

Renewable Spirits, LLC
 

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